Midterm 1 Flashcards

Question

Rank the following in terms of size (smallest --> largest) Bacteria and archaea Eukaryotic Cells Viruses

Answer 1

viruses < bacteria and archaea < eukaryotic cells

Answer 2

There is less predation when the bacterial cell is larger than eukaryotes because it makes it harder for the eukaryotes to ingest it

Answer 3

Can act as parasites for other bacteria if they have a small genome through which they can't make amino acids and vitamins This means they can take away resources from the cells they are attached to

Answer 4

1. Cocci (s. coccus) - spherical e.g. Staphylococcus aureus 2. Bacilli (s. bacillus) - rods e.g. Legionella pneumophila 3. Spirals e.g. Campylobacter jejuni

Answer 5

Shape can impact - motility (capable of moving by themselves, shape can determine how well they move) - pathogenesis (ability to cause disease) - ability to evade predators, immune system

Answer 6

Yes. For example uropathogenic E. coli forms long, linear filaments when leaving cells which protects from immune system

Answer 7

- grow at very high temps ( >100 C) - membranes more viscous (branched, saturated fatty acids. thermostable lipids) - thermostable proteins (more intramolecular interactions)

Answer 8

To counter the denaturing. It acts to keep it folded in the proper shape

Answer 9

Autoclave is a device used to kill bacteria (makes sure things are sterile through high pressurized steam)

Answer 10

- Grow at low temps - make cryoprotectants, antifreeze proteins (prevent ice from forming, protect membranes) - membranes have more UNsaturated fatty acids (to keep them more fluid) - proteins are more flexible (fewer H-bonds, ionic interactions, etc)

Answer 11

Because the proteins need to be able to move better

Answer 12

- grow at low pH - keep cytoplasm near neutrality (exclude/pump out H+) - surface proteins acid stable - intracellular proteins work best at neutral pH

Answer 13

So that they are less susceptible to hydrolysis

Answer 14

- grow at high pH - some live in soda lakes (high salt conc. with pH 9-12) - keeps cytoplasm near neutrality (increase H+ uptake, retention, produce acidic metabolites) - extracellular enzymes (e.g. proteases) work at high pH

Answer 15

Where one benefits and the other is not benefited/harmed

Answer 16

- Nutrient digestion - Vitamin production (e.g., B12, K) - Maintaining immune system (can maintain it in an alert state) - Blocking disease-causing organisms ("colonization resistance")

Answer 17

c) needs to be viscous to protect against them falling apart

Answer 18

Liquid media (e.g., broth cultures) Solid media (e.g., agar plates)

Answer 19

Only one strain On agar plates, bacteria form colonies. Each colony is usually derived from a single cell, We can use a colony to inoculate a pure culture.

Answer 20

Defined media, complex media, differential media and selective media

Answer 21

Synthetic; known composition - can use to study nutritional needs (e.g. minimum requirements for growth aka minimal media) - avoids complication of complex medium components (less batch-to-batch variability)

Answer 22

Contains more complex ingredients (can contain partially hydrolyzed animal tissues, milk, yeast) - E.g. peptone, tryptone, yeast extract - composition not fully defined - very rich; can support many species - useful for bacteria with unknown nutritional requirements

Answer 23

distinguishes between different kinds of bacteria e.g. blood agar - used to detect hemolytic bacteria (bacteria that are capable of degrading RBC) - hemolysis is defining feature of some pathogens (different kinds of hemolysis) - doesn't favour or disfavour certain species

Answer 24

alpha-hemolysis beta-hemolysis gamma-hemolysis

Answer 25

Definition: Alpha-hemolysis is a partial or incomplete hemolysis of red blood cells. Mechanism: In this process, the hemoglobin within the red blood cells is oxidized, leading to a greenish discoloration on blood agar plates. Appearance on Blood Agar Plates: Alpha-hemolysis is often seen as a narrow zone of greenish discoloration surrounding bacterial colonies grown on blood agar plates. Example Bacteria: Streptococcus pneumoniae is a common bacterium associated with alpha-hemolysis.

Answer 26

Definition: Beta-hemolysis is complete or full hemolysis of red blood cells. Mechanism: Bacteria producing beta-hemolysins release substances that completely break down the hemoglobin in red blood cells, resulting in the complete destruction of the cells. Appearance on Blood Agar Plates: Beta-hemolysis is characterized by a clear zone surrounding bacterial colonies on blood agar plates. The clearing is due to the complete lysis of red blood cells, leaving an empty space around the colonies. Example Bacteria: Streptococcus pyogenes is an example of a bacterium associated with beta-hemolysis.

Answer 27

Definition: Gamma-hemolysis is not hemolysis at all; there is no significant interaction between the bacteria and red blood cells. Mechanism: The term "gamma" here implies no change or activity regarding hemolysis. The bacteria do not cause damage to red blood cells. Appearance on Blood Agar Plates: There is no observable zone of hemolysis around the bacterial colonies on blood agar plates. Example Bacteria: Many bacteria fall into this category, as they do not exhibit hemolytic activity. For example, some strains of Enterococcus faecalis may display gamma-hemolysis.

Answer 28

Types of culture media designed to either support the growth of specific microorganisms or inhibit the growth of unwanted ones. Used in microbiology for isolating and identifying specific bacterial species from complex samples. Example - MacConkey Agar: Selective for: Gram-negative bacteria Inhibition of: Gram-positive bacteria through bile salts and crystal violet Differential Properties: Allows differentiation based on lactose fermentation Lactose Fermentation: lac+ bacteria produce acidic by-products pH Indicator: Neutral red turns red under acidic conditions Summary: MacConkey agar is both selective (for Gram-negatives) and differential (based on lactose fermentation), aiding in the isolation and identification of specific bacterial groups.

Answer 29

In the context of microbiology and laboratory techniques, "differential" refers to the ability of a medium (such as agar) or a test to distinguish between different microorganisms or groups of microorganisms based on their specific characteristics or behaviors. For example, in a differential medium, different types of bacteria may produce distinct observable changes in the medium, such as changes in color, precipitation, or the formation of specific growth patterns. These variations help microbiologists identify and differentiate between bacterial species or strains. In summary, a medium or test is considered differential if it allows for the discrimination between different microorganisms based on certain observable features or reactions.

Answer 30

In a non-differential or simple medium, the goal is to support the growth of a wide range of microorganisms without providing specific features for differentiation. These media typically contain basic nutrients required for bacterial growth but lack indicators or components that would reveal differences in the metabolic or biochemical properties of the microorganisms. In non-differential media, all microorganisms may appear similar, and there is no specific attempt to distinguish between different types based on observable changes in the medium. Non-differential media are often used when the primary goal is to culture and maintain a broad spectrum of microorganisms without the need for detailed differentiation.

Answer 31

Binary fission

Answer 32

- Chromosome is replicated - Cell elongates - Septum forms, chromosomes partitioned - Daughter cells separate

Answer 33

FtsZ is a tubulin-like protein that forms a Z ring in the middle of the bacterial cell. It accumulates in the center of the cell, forming a ring, and is crucial for initiating the cell division process.

Answer 34

The division complex forms at the Z ring, and as the Z ring constricts, it invaginates the membrane, pulling the ring towards the center of the cell. This process also pulls the membrane and the cell wall with it.

Answer 35

The contraction of the Z ring leads to the invagination of the membrane, pulling the ring towards the center of the cell. Simultaneously, it pulls the membrane and the cell wall, contributing to the formation of the division septum.

Answer 36

The division complex, formed at the Z ring, is responsible for constricting the ring, invaginating the membrane, and pulling the membrane and cell wall towards the center of the cell. This process ultimately results in the formation of the division septum, composed of peptidoglycan.

Answer 37

Budding is a bacterial replication strategy where a small, new cell, or bud, emerges from the surface of the parent cell. The bud gradually enlarges and eventually separates, forming a new, independent bacterial cell.

Answer 38

Spore formation is a bacterial replication strategy where a bacterial cell undergoes sporulation to produce a durable, resistant spore. The spore is a dormant form that can withstand harsh conditions, ensuring the survival of the bacterium in unfavorable environments.

Answer 39

Budding involves the emergence of a small bud from the parent cell, gradually growing into a new cell. In contrast, binary fission is the division of a bacterial cell into two identical daughter cells.

Answer 40

Spore formation allows bacteria to withstand adverse environmental conditions. The spore is a highly resistant and durable structure, ensuring the survival of the bacterium in conditions that may be detrimental to the vegetative cell.

Answer 41

It grows exponentially, since the population doubles every time it divides

Answer 42

Binary fission results in the formation of two identical daughter cells from a single parental bacterial cell.

Answer 43

Generation time, also known as doubling time, is the time required for a bacterial population to double in size. It serves as a measure of the growth rate of a bacterial population.

Answer 44

The generation time is condition-dependent and varies among bacterial species. For example, E. coli has a generation time of approximately 20 minutes, while M. tuberculosis has a longer generation time of about 12 hours

Answer 45

A batch culture refers to a closed vessel containing a single batch of growth medium. Bacteria are inoculated into this medium to study their growth dynamics over time.

Answer 46

The bacterial growth curve in a batch culture consists of four phases: lag phase, exponential (log) phase, stationary phase, and death (decline) phase.

Answer 47

The lag phase is the initial phase of the bacterial growth curve, characterized by a period of adaptation and preparation for growth. During this phase, there is little to no increase in the cell count.

Answer 48

The exponential phase is a phase of rapid bacterial growth in the curve. The population increases exponentially, and the graph shows a steep incline in the log of viable cell count.

Answer 49

The stationary phase is a phase in the bacterial growth curve where the growth rate slows down, and the number of new cells produced is balanced by the number of dying cells. The log of viable cell count remains relatively constant during this phase.

Answer 50

The death phase is the final phase in the bacterial growth curve, characterized by a decline in the number of viable cells. This may be due to nutrient depletion or the accumulation of waste products.

Answer 51

During the lag phase, cell numbers stay constant initially. Metabolic activity increases as cells get ready to divide. Cells perform tasks like making ATP, ribosomes, and enzyme co-factors. Cellular components undergo repair. Adaptation to nutrients present occurs. Production of transporters and catabolic enzymes takes place.

Answer 52

Cell number increases exponentially. Graph shows a straight line during this phase. Cells divide as fast as possible, influenced by species/strain, growth medium, and environmental conditions (e.g., temperature, oxygen). The population is uniform and metabolically active.

Answer 53

Growth slows due to limited nutrients. Accumulation of toxic waste products. High cell density (~10^9 cells/mL). Viable cell count stabilizes. Cells remain metabolically active but division slows. Balance between division and death.

Answer 54

Little nutrients, abundant waste. Decrease in viable cell numbers. Cell death occurs. Some cells become viable but nonculturable due to stress response. Programmed cell death in some. Nutrient release through "altruism." May last for months to years, contributing to evolutionary processes.

Answer 55

A) to estimate viable cell count

Answer 56

C. Living and dead cells may appear similar.

Answer 57

C. to estimate viable cell count

Answer 58

Cells directly counted with a counting chamber (e.g., Petroff-Hausser). Sample pipetted under coverslip. Counting done using a microscope. Cells/mL calculated using grid size and chamber volume. Living and dead cells may appear similar in this method.

Answer 59

C. Cells are added to an agar plate, and the number of colonies is counted.

Answer 60

B. Colony-Forming Units

Answer 61

A. One colony can come from more than one cell.

Answer 62

B. Plate counts give smaller counts than direct counts.

Answer 63

CFUs represent the number of viable cells that give rise to a single visible colony on an agar plate.

Answer 64

The "Great plate count anomaly" refers to the observation that plate counts are usually smaller than direct counts. This discrepancy is due to factors like the exclusion of living cells, inclusion of dead cells, and the inability to count viable but nonculturable cells.

Answer 65

In viable counting methods, a sample is added to an agar plate, and the number of visible colonies that grow is counted. This method allows the enumeration of only viable cells, providing Colony-Forming Units (CFUs) as an estimate.

Answer 66

Plate counting is unable to differentiate between living and dead cells, as both can form visible colonies on agar plates.

Answer 67

1,800 CFU/mL explanation: Number of Colonies = 90 Volume of Plated Sample = 0.5 mL Dilution Factor = 1/10 CFU/mL = 90/(0.5 × 1/10) = 90/0.05 = 1800

Answer 68

CFU/mL= number of colonies/(Volume of Plated Sample×Dilution Factor)

Answer 69

Cells scatter light, and absorbance (optical density; OD) is related to the number of cells. Dead cells also contribute to light scattering.

Answer 70

Low cell density results in low absorbance/OD. High cell density leads to high absorbance/OD.

Answer 71

Factors such as osmolarity, pH, temperature, and oxygen levels influence microbial growth. Microbes are adapted to specific environments, and their protein activities, membrane composition, and metabolic pathways are shaped accordingly.

Answer 72

Examples include osmolarity, pH, temperature, and oxygen levels.

Answer 73

Osmosis is the movement of water through a semi-permeable membrane driven by different solute concentrations. Bacterial membranes are semi-permeable, allowing water to cross freely through aquaporins and diffusion. The cytoplasm of bacteria has a high solute concentration.

Answer 74

Isotonic solution: Osmolarity is the same as the cell. Hypertonic solution: Osmolarity is higher than the cell. Hypotonic solution: Osmolarity is lower than the cell.

Answer 75

Isotonic solution: No net movement of water. The osmolarity is the same inside and outside the cell.

Answer 76

Water leaves the cell, leading to cytoplasm shrinkage, a process known as plasmolysis.

Answer 77

Water enters the cell, causing cytoplasm to swell. This condition can lead to osmotic lysis.

Answer 78

True, it is NOT impacted by the osmolarity of the environment

Answer 79

Response to hypertonic conditions: Plasmolysis occurs, causing membrane damage. Dehydration in hypertonic conditions slows the growth of bacterial cells.

Answer 80

Cell processes are typically optimal in around 70% water. Hypertonic conditions, leading to dehydration, can adversely affect the efficiency of cell processes.

Answer 81

Some bacteria produce compatible solutes. Compatible solutes are not toxic at high levels (>1 M) and serve to increase the osmolarity of the cytoplasm, helping the cell adapt to hypertonic environments.

Answer 82

Bacteria prevent plasmolysis by producing large concentrations of compatible solutes. Compatible solutes increase the cytoplasm's osmolarity, counteracting the hypertonic environment and maintaining cellular integrity.

Answer 83

Bacteria can survive hypotonic conditions by exporting solutes. Mechanosensitive channels, regulated by the stretching of the cytoplasmic membrane, play a key role. - When the membrane is stretched, these channels open, allowing solutes to leave, which decreases cytoplasmic osmolarity and osmotic pressure.

Answer 84

Mechanosensitive channels regulate the stretching of the cytoplasmic membrane in hypotonic conditions. When stretched, these channels open, allowing solutes to leave, decreasing solute concentration in the cytoplasm. Decreasing solute concentration reduces the osmotic pressure, preventing excessive water influx and minimizing membrane stretching.

Answer 85

c) Produce large amounts of compatible solutes in the cytoplasm plasmolysis occurs when water is drawn out of the cytoplasm, so it wants to prevent water leaving. by producing compatible solutes it increases osmolarity therefore increasing the water entering the cytoplasm

Answer 86

Acidophiles: Optimal pH < 5.5 Neutrophiles: Optimal pH 5.5 – 8.0 Alkaliphiles: Optimal pH > 8.0

Answer 87

pH changes can disrupt the cytoplasmic membrane and impact protein activity. The optimal cytoplasmic pH is maintained near neutral pH.

Answer 88

Bacteria can maintain cytoplasmic pH near neutral by importing or exporting protons.

Answer 89

Temperature influences enzyme activity, with activity increasing as temperature rises. However, enzymes can denature and lose activity at temperatures beyond a certain point.

Answer 90

Temperature impacts membrane viscosity. In low temperatures, bacteria incorporate more unsaturated fatty acids. In high temperatures, bacteria need more saturated and branched fatty acids. They may also increase the presence of ether lipids, which are more resistant to hydrolysis.

Answer 91

Proteins in bacterial cells prevent DNA melting at high temperatures, contributing to the stability of the genetic material.

Answer 92

Mesophiles are organisms that thrive at moderate temperatures. The optimal growth temperature for mesophiles is typically around 37 °C, which is close to human body temperature. (they are adapted to grow best in our bodies)

Answer 93

Psychrophiles are organisms adapted to cold temperatures. They are commonly associated with refrigerated environments and can contribute to the spoilage of refrigerated food.

Answer 94

Oxygen is essential for some bacteria but toxic to others. It damages cellular components by oxidizing sensitive groups, such as cysteines.

Answer 95

Reactive oxygen species (ROS) are formed by the reaction of oxygen with cellular components. ROS can react with proteins, lipids, and nucleic acids, causing damage to these biomolecules.

Answer 96

Bacterial enzymes, like catalase, play a protective role against oxygen toxicity. Catalase, for example, helps break down hydrogen peroxide, a reactive oxygen species, preventing its harmful effects.

Answer 97

Bacterial growth depends on metabolic pathways and the presence of ROS scavenging enzymes.

Answer 98

Obligate aerobes require oxygen for growth. Anaerobes can grow without oxygen, while oxygen is detrimental to obligate anaerobes. Facultative anaerobes can grow with or without oxygen, but oxygen is beneficial rather than essential.

Answer 99

Oxygen does not impact aerotolerant anaerobes. Microaerophiles require low oxygen levels and cannot survive at atmospheric levels.

Answer 100

The tube has a gradient with the top being oxic (containing oxygen) and the bottom being anoxic (without oxygen).

Answer 101

Different kinds of bacteria exhibit varied growth patterns along the gradient, with preferences for oxic or anoxic conditions.

Answer 102

Physical methods, such as changing temperature and osmolarity, can be employed to control bacterial growth. For example, heat can denature proteins, degrade DNA, and disrupt membranes.

Answer 103

Autoclaving is a sterilization method that uses high-pressure steam. It effectively kills bacteria by subjecting them to high-pressure steam, ensuring thorough sterilization.

Answer 104

Pasteurization is a method to kill pathogens using moderate heat. It involves heating a substance, such as liquid or food, to a temperature that is sufficient to kill pathogens but not high enough to compromise the quality of the substance.

Answer 105

Cold slows down metabolic processes, making it an effective method for controlling bacterial growth. Refrigeration is a common application of cold to slow down bacterial growth in various contexts.

Answer 106

Hypertonic conditions slow microbial growth by inducing dehydration and plasmolysis in cells. High salt concentrations (e.g., in cured meats) and high sugar concentrations (e.g., in honey and jams) are examples of hypertonic conditions used to control bacterial growth.

Answer 107

Acidic and alkaline conditions slow bacterial growth by impacting protein function. Examples include acidic foods like pickles and jams.

Answer 108

Many chemicals have general targets in bacteria, such as proteins, DNA, and lipids.

Answer 109

Disinfectants are used for inanimate objects (e.g., bleach). Antiseptics are used on living tissue (e.g., rubbing alcohol).

Answer 110

Antibiotics have very specific targets in bacteria, such as the cell wall or ribosomes. These bacterial features are absent or different in human cells, making antibiotics often safer compared to chemicals with more general targets.

Answer 111

Oligotrophic environments

Answer 112

Due to the high level of competition among bacteria

Answer 113

Nutrients are in forms that resist breakdown, such as complex organic polymers

Answer 114

Bacteria in oligotrophic environments have very long generation times (months, years), while lab conditions may allow for rapid growth (e.g., 20 minutes for E. coli)

Answer 115

There are not many nutrients present, and if they become available, there is intense competition for these limited resources. Many of the nutrients are in forms that resist breakdown, such as complex organic polymers.

Answer 116

Stringent response

Answer 117

Overall cell metabolism decreases.

Answer 118

Genes for growth are downregulated.

Answer 119

Stress response genes are upregulated, producing proteins that protect DNA, cell wall, etc.

Answer 120

They protect cells from damage, toxic chemicals, etc., making the cells more difficult to kill.

Answer 121

Persistor cells

Answer 122

Persistor cells can form during starvation and also under normal conditions, often in response to other stresses.

Answer 123

Antibiotics work best against actively growing cells, and persistor cells are growth-arrested.

Answer 124

Persistor cells can contribute to recurrent infections.

Answer 125

In infections, some bacterial cells, like persistors, may not be affected. For instance, antibiotics targeting the ribosome won't be very effective against cells that don't utilize the ribosome.

Answer 126

Starvation can induce the formation of endospores, primarily observed in Gram-positive bacteria like Bacillus and Clostridium.

Answer 127

Endospores have a distinct structure and composition compared to normal cells but contain the same DNA.

Answer 128

Similar to persisters, endospores are metabolically inactive.

Answer 129

Endospores form inside the vegetative mother cell, which is in a growing, metabolically active state.

Answer 130

Endospores are released by lysis of the mother cell.

Answer 131

Endospores are highly resistant to heat, UV light, desiccation, and are protected from chemicals, antibiotics, and phages due to an impermeable surface.

Answer 132

Extreme measures, such as autoclaving, are needed to effectively eliminate endospores.

Answer 133

Endospores enhance survival in challenging environments, allowing bacteria to endure unfavorable conditions.

Answer 134

Endospores re-form into vegetative cells under specific and favorable conditions.

Answer 135

The core of an endospore contains the nucleoid, ribosomes, and other essential components.

Answer 136

Proteins surrounding the core protect the DNA from heat, UV, and chemical damage.

Answer 137

The core is surrounded by the cortex (peptidoglycan), coat (protein layers), and, although not shown, the exosporium.

Answer 138

The core wall and coat of an endospore are impermeable, preventing the passage of substances in and out of the endospore.

Answer 139

Sterilization is required to kill endospores, especially in medical devices.

Answer 140

Botulism is a health concern related to Clostridium botulinum spores, particularly in improperly home-canned foods where spores can germinate and produce botulinum toxin.

Answer 141

Bacillus anthracis spores cause anthrax, which can manifest as cutaneous anthrax (skin infection, not as harmful when treated) or pulmonary anthrax (spores inhaled, potentially leading to septic shock and death)

Answer 142

In the lab, bacteria are usually planktonic (free-floating), while in the environment, most bacteria live in biofilms.

Answer 143

Biofilms are communities of cells embedded in a slimy matrix known as extracellular polymeric substances (EPS).

Answer 144

Biofilms can form on various surfaces, including medical devices such as catheters and artificial valves, as well as host tissues like teeth.

Answer 145

Biofilm formation requires cells to work together, and quorum sensing (QS) is the mechanism that enables this cooperation.

Answer 146

Quorum sensing involves cells secreting autoinducer (AI) molecules, and the concentration of AI is related to the number of cells. This concentration controls gene expression, particularly in biofilm formation.

Answer 147

At high AI concentrations, bacteria in biofilms might become more adhesive, leading to the production of structures like pili, and produce extracellular polymeric substances (EPS).

Answer 148

In biofilm formation, planktonic bacteria adhere to a surface, transitioning to a sessile state.

Answer 149

After adhesion, cells divide and form microcolonies, contributing to the growth of the biofilm.

Answer 150

In a biofilm, cells stick to each other, and they also adhere to the extracellular polymeric substances (EPS).

Answer 151

Other bacteria can join a biofilm, and bacterial cells within a biofilm have the ability to disperse.

Answer 152

The term "sessile state" in biofilm formation refers to the state of bacteria when they have adhered to a surface and become stationary or attached, as opposed to their free-floating, planktonic state.

Answer 153

Bacteria can attach to host cells using adhesins, such as pili, interacting with molecules like sugars and proteins.

Answer 154

Bacterial attachment is specific when adhesins, such as pili, have specificity for certain molecules, like sugars and proteins.

Answer 155

Bacteria can attach to abiotic surfaces using non-specific mechanisms, involving bacterial components like lipopolysaccharide.

Answer 156

Surfaces can be conditioned, for example, when indwelling medical devices get coated by host proteins, aiding bacterial attachment.

Answer 157

Bacteria can attach to early colonizers and EPS, contributing to the development and stability of biofilms.

Answer 158

EPS in biofilms forms a slime-like matrix composed of glycoproteins, polysaccharides, DNA, and other substances.

Answer 159

Some EPS are secreted, while others are released by cell death (e.g., DNA). Components include glycoproteins, polysaccharides, and DNA.

Answer 160

EPS helps bacteria stick to biofilms, traps nutrients, and forms channels that distribute nutrients within the biofilm.

Answer 161

EPS retains secreted digestive enzymes near bacterial cells within the biofilm.

Answer 162

EPS is highly hydrated, contributing to the overall slimy and hydrated nature of the biofilm matrix. less likely to undergo dehydration and plasmolysis

Answer 163

Surfaces can be preconditioned by molecules present in the environment. This preconditioning allows bacteria to attach to these surfaces more effectively.

Answer 164

Preconditioned surfaces are crucial for bacterial attachment. In medical applications, this is significant, for instance, in the case of catheters.

Answer 165

Biofilms allow bacteria to better tolerate rough environments by providing a protective matrix that shields them from external stresses.

Answer 166

Bacteria embedded in the biofilm matrix may have improved nutrient availability, as the matrix can trap and distribute nutrients more effectively.

Answer 167

The structure of biofilms creates nutrient and oxygen gradients, with cells near the surface having better access to nutrients.

Answer 168

Cells near the surface of biofilms are more metabolically active, similar to planktonic cells, and can dispose of waste more easily.

Answer 169

Cells in the middle of biofilms experience limited nutrients and oxygen, leading to a dormant state, which is favorable for anaerobes.

Answer 170

The structure creates nutrient and oxygen gradients, allowing cells near the surface to access nutrients, making them more metabolically active and similar to planktonic cells.

Answer 171

Cells in the middle of biofilms can become dormant, and this environment favors the growth of anaerobes.

Answer 172

The structure creates gradients leading to waste accumulation, but cells near the surface can dispose of waste more easily compared to cells in the middle.

Answer 173

Biofilms can thrive in nutrient-poor environments by trapping nutrients, digestive enzymes, and utilizing waste and lysed cells, creating a conducive nutritional environment.

Answer 174

Biofilms promote genetic diversity by facilitating the acquisition of new DNA, leading to the evolution of novel properties within bacterial communities.

Answer 175

Extracellular polymeric substances (EPS) in biofilms act as a protective barrier, shielding bacteria from predators, UV light, desiccation, and other environmental challenges.

Answer 176

Bacteria in biofilms can assimilate new DNA, fostering genetic diversity. This process may lead to the acquisition of properties, including antibacterial resistance, through the uptake of relevant genes.

Answer 177

Bacteria release products within a biofilm, creating interconnected ecosystems where each organism benefits others, contributing to the overall functionality of the microbial community.

Answer 178

Biofilms make it challenging for predators to surround and kill bacteria due to the complex structure. Additionally, the biofilm shields bacteria from UV light, and the moisture within reduces the risk of dehydration.

Answer 179

Biofilms play a significant role in endocarditis, where they can form on heart valves, contributing to the severity of the infection.

Answer 180

Biofilm-related urinary tract infections are prevalent, often associated with the use of catheters.

Answer 181

Biofilms are known to contribute to corneal infections, especially in individuals using contact lenses.

Answer 182

Dental plaque is a biofilm that forms on teeth surfaces, contributing to oral health issues such as cavities and gum disease.

Answer 183

Biofilms enhance host colonization by providing a protected environment for bacteria. They also serve as reservoirs of cells, contributing to recurrent infections.

Answer 184

Biofilms can protect bacteria by some cells getting stuck to the extracellular polymeric substances (EPS), creating a physical barrier that limits the effectiveness of antimicrobial agents.

Answer 185

Persister cells within biofilms exhibit reduced susceptibility to antimicrobials, making them more resistant to treatment and contributing to the persistence of biofilm-related infections.

Answer 186

Biofilms limit immune clearance by making bacteria less accessible to immune cells and antibodies. The complex biofilm structure hinders the immune system's ability to effectively target and eliminate the bacterial population.

Answer 187

The microbiome or microbiota encompasses all microbes, including bacteria, living in and on the human body.

Answer 188

Bacteria occupy various niches in and on the body, adapting to specific conditions such as nutrient availability, oxygen levels, pH, and other environmental factors unique to each niche.

Answer 189

The immune system recognizes and destroys microbes, playing a vital role in maintaining the body's health.

Answer 190

The innate immune response is nonspecific and serves as the first line of defense against pathogens, providing immediate protection upon encountering a threat.

Answer 191

The adaptive immune response is specific and slower to respond to unfamiliar pathogens, providing targeted and precise defense mechanisms against specific threats.

Answer 192

The physical barriers of innate immunity include the skin and mucous membranes, acting as the first line of defense against pathogens.

Answer 193

Phagocytes engulf and destroy bacterial cells, recognizing common features and playing a crucial role in eliminating pathogens from the body.

Answer 194

Chemical mediators such as antimicrobial peptides and complement (>30 serum proteins) are part of innate immunity. They promote inflammation, form holes in cell walls, and assist phagocytes in recognizing bacteria through opsonization.

Answer 195

The complement system, with over 30 serum proteins, forms holes in bacterial cell walls, promotes inflammation, and aids phagocytes in recognizing bacteria through opsonization.

Answer 196

In opsonization, the complement protein C3b binds to the surface of the bacterium, marking it for recognition and destruction.

Answer 197

Phagocytes, such as those with C3b receptors (e.g., C3b receptor), bind to the C3b on the surface of the bacterium, initiating the process of phagocytosis.

Answer 198

Phagocytosis involves the bacterium being taken into a phagosome, which subsequently fuses with a lysosome. This fusion leads to the degradation of the bacterium within the phagolysosome.

Answer 199

The adaptive immune response is initiated by the innate immune response. Dendritic cells (DCs), a type of phagocyte, play a crucial role in activating the adaptive response.

Answer 200

Dendritic cells degrade bacterial proteins (antigens) and display them on their surface. This presentation of antigens activates T cells and B cells, key players in the adaptive immune response.

Answer 201

B cells, when activated by dendritic cells, produce antibodies that bind to specific antigens. These antibodies play a crucial role in the immune response against bacteria.

Answer 202

Antibodies bind to bacteria, and this process is known as opsonization. Phagocytes then recognize the antibodies, enhancing the efficiency of bacterial clearance.

Answer 203

The majority of microbiota are commensals, organisms that coexist with the host without causing harm or benefit.

Answer 204

Pathogenic bacteria have the ability to cause infections and diseases, a characteristic known as pathogenicity.

Answer 205

Commensals exclude pathogens by competing for nutrients and space, producing inhibitory substances, and altering environmental conditions (e.g., pH) to create an environment less conducive to pathogen growth.

Answer 206

Commensals can become opportunistic pathogens, causing disease when the host's defenses are compromised. For example, E. coli can lead to urinary tract infections if they leave where they were originally present.

Answer 207

Virulence represents the severity of the disease caused by pathogens. It is influenced by factors such as the pathogen's ability to cause infection and the impact on the host.

Answer 208

Virulence factors are cell structures, toxins, or other elements possessed by pathogens that enhance their ability to cause infection, influencing the severity of the disease.

Answer 209

Bacterial infections consist of the following components: 1. Adhesion - Attachment to host cells. 2. Proliferation - Rapid multiplication of bacterial cells. 3. Invasion - Penetration into host tissues. 4. Tissue damage - Harm caused to host tissues, contributing to the overall impact of the infection.

Answer 210

Pathogens can enter the body through various routes, including the skin, inhalation, and ingestion.

Answer 211

The body employs clearance mechanisms such as swallowing, mucociliary escalator (respiratory system), and urination to remove bacteria and prevent infections. Note: (The mucociliary escalator is a defense mechanism in the respiratory system that uses cilia and mucus to move inhaled particles, including bacteria, upward and out of the respiratory tract. This process helps prevent the entry and establishment of pathogens in the lungs.)

Answer 212

To infect the host, pathogens must adhere and colonize. They use adhesins, such as pili and capsules, to facilitate attachment to host cells.

Answer 213

Some pathogens form biofilms, which are communities of microorganisms surrounded by a protective matrix. Biofilms contribute to increased adhesion and colonization, making it easier for pathogens to establish infections.

Answer 214

Invasion allows pathogens to access more nutrients and encounter less competition, aiding in their survival and replication within host cells and tissues.

Answer 215

Active penetration involves the use of virulence factors, such as enzymes that degrade the extracellular matrix and break cell-cell connections, facilitating the pathogen's entry into host cells and tissues.

Answer 216

Passive penetration follows an unrelated event, such as injury causing damage to the skin. In these situations, pathogens can enter host tissues due to the compromised barrier.

Answer 217

Pathogens must overcome the immune system to successfully invade host cells and tissues, making immune evasion a critical strategy for their survival.

Answer 218

Pathogens can employ various strategies to avoid recognition by antibodies, including decreasing the amount of antigen, modifying antigen structures (e.g., subunits of pili, flagella), and hiding antigens with structures like capsules.

Answer 219

Pathogens can interfere with the immune response by degrading antibodies and complement proteins, hiding bound antibodies from phagocytes, and utilizing structures like capsules and biofilms.

Answer 220

Pathogens can bind to antibodies, inhibiting opsonization. For example, S. aureus protein A binds to the Fc region of antibodies, preventing the usual opsonization process.

Answer 221

Some pathogens bind antibodies in unproductive ways, leaving the Fc domain unbound. This prevents macrophages from recognizing the pathogen because the Fc region, crucial for macrophage binding, is not available. Consequently, the pathogen remains unrecognized, avoiding efficient immune clearance.

Answer 222

Opsonization is a process in the immune system where pathogens are coated with antibodies or complement proteins, making them more recognizable to phagocytic cells for efficient engulfing and removal

Answer 223

Some pathogens produce toxins causing tissue damage, even without an active infection. There are two main types of toxins: 1. Endotoxins: Key component of the cell wall, specifically lipopolysaccharide (LPS). They are released only if the bacterium is lysed, leading to systemic effects like fever and shock. Endotoxins can activate severe responses, potentially causing conditions like septic shock. 2. Exotoxins: Proteins or enzymes released by the bacterial cell. Unlike endotoxins, the bacterial cell does not need to be lysed. Exotoxins tend to be very dangerous and can target host cell functions and metabolism. They may be tissue-specific, such as neurotoxins.

Answer 224

Staphylococcus aureus is a common part of the normal microbiota but can also cause infections, such as skin and soft tissue infections.

Answer 225

MRSA stands for Methicillin-resistant Staphylococcus aureus. It has acquired the mecA gene, making it less susceptible to β-lactam antibiotics like penicillin G and methicillin.

Answer 226

Adding approximately 2,000 to 3,000,000 base pairs (bp) to the genome transforms Staphylococcus aureus into MRSA, creating a 'superbug' resistant to certain antibiotics.

Answer 227

MRSA is a major cause of nosocomial (hospital-acquired) infections and is difficult to treat due to its resistance to common antibiotics, posing a higher risk compared to regular Staphylococcus aureus infections.

Answer 228

In Canada, 1 in 5 MRSA bloodstream infections are lethal, highlighting the severity and potentially life-threatening nature of MRSA infections.

Answer 229

Genetic variation in bacteria is crucial as it allows them to adapt to selective pressures, such as antibiotics. This variation is the basis of evolution, enabling bacteria to survive and thrive in changing environments.

Answer 230

Genetic variation in bacteria occurs through changes to DNA. Unlike binary fission, which doesn't generate diversity, bacteria undergo genetic changes through mutations, acquiring new DNA, and recombination.

Answer 231

Changing DNA is the foundation of bacterial evolution. It enables bacteria to evolve and respond to environmental challenges, ensuring their survival by developing traits that enhance their adaptability and resistance to various conditions, including antibiotics.

Answer 232

Bacteria acquire genetic diversity through mutations, which are changes in their DNA sequence, as well as by acquiring new DNA from their surroundings and undergoing recombination, contributing to the overall genetic variation within bacterial populations.

Answer 233

Binary fission, the method of bacterial cell division, does not generate diversity because it results in identical daughter cells. Genetic diversity arises from mechanisms like mutations, DNA acquisition, and recombination, which binary fission lacks, making these processes essential for bacterial adaptation and evolution.

Answer 234

Random changes to DNA sequence include substitutions, deletions, insertions, and other alterations. These changes can impact the genetic information carried by an organism.

Answer 235

Yes, mutations are inheritable. They can be passed on to the next generation if they occur in the germ cells (sperm or egg cells) of an organism.

Answer 236

Spontaneous mutations can arise due to errors during DNA replication. These errors may occur naturally and are not induced by external factors.

Answer 237

Mobile genetic elements, such as transposons, can move within the genome, causing mutations by changing their position or promoting rearrangements in the DNA sequence.

Answer 238

Mutations can be induced by external factors known as mutagens. Examples include chemicals that modify DNA and environmental factors like ultraviolet light.

Answer 239

Mutations can impact gene sequences and gene expression levels, potentially leading to changes in the function or regulation of genes within an organism.

Answer 240

Mutations can affect gene expression levels by altering the regulatory elements or sequences that control how genes are turned on or off. This, in turn, can impact the production of proteins and other cellular processes.

Answer 241

Induced mutations can originate from various sources, including exposure to mutagenic chemicals and environmental factors like ultraviolet light. These external agents can introduce changes in the DNA sequence, leading to mutations.

Answer 242

It might introduce additional mutations

Answer 243

Most DNA is passed from the mother cell to daughter cells through vertical gene transfer, where genetic material is inherited vertically from parent to offspring during cell division.

Answer 244

Horizontal gene transfer (HGT) is the transfer of genetic material between different bacteria, allowing for the acquisition of new DNA from sources other than the parental lineage.

Answer 245

Yes, bacteria can acquire DNA from sources other than vertical gene transfer through horizontal gene transfer mechanisms.

Answer 246

Newly acquired DNA must integrate into the bacterial genome or replicate independently for it to be maintained. Otherwise, it may be lost during subsequent generations.

Answer 247

Horizontal gene transfer is significant in bacterial evolution as it allows for the rapid exchange of genetic material between different bacterial strains, contributing to the diversity and adaptability of bacterial populations.

Answer 248

Bacteria can integrate or replicate independently acquired DNA through processes like recombination, where the new DNA aligns with the existing genome, ensuring its stability and integration into the bacterial genetic material.

Answer 249

If newly acquired DNA is not integrated or replicated independently, it is at risk of being lost during subsequent cell divisions, leading to the loss of potentially advantageous traits or genetic information.

Answer 250

upregulate or downregulate

Answer 251

Vertical = transfer from parent --> child Horizontal = external sources

Answer 252

Recombination refers to the process in which one or more DNA molecules are rearranged or combined, resulting in a new DNA sequence. This process plays a crucial role in generating genetic diversity in bacterial populations.

Answer 253

DNA recombination produces new DNA sequences, leading to various outcomes such as the creation of novel genetic combinations and the introduction of genetic diversity within a population.

Answer 254

The two main types of DNA recombination are homologous recombination, involving DNA with similar sequences, and site-specific recombination, which occurs between DNA molecules without extensive homology.

Answer 255

Homologous recombination involves DNA with similar sequences. During this process, genetic material from two homologous DNA molecules is exchanged, leading to the creation of hybrid DNA sequences.

Answer 256

Site-specific recombination involves DNA molecules without extensive homology. It is a targeted process where specific DNA sequences are recognized, and rearrangements occur at those defined sites, facilitating the integration or excision of genetic material.

Answer 257

Homologous recombination contributes to genetic diversity by facilitating the exchange of genetic material between similar DNA sequences. This process can result in the formation of hybrid DNA sequences and the introduction of new genetic traits into bacterial populations.

Answer 258

Site-specific recombination is significant for targeted genetic rearrangements. It allows for specific changes in the DNA sequence at predetermined sites, influencing gene regulation, expression, and the incorporation or removal of genetic elements in a controlled manner.

Answer 259

Site-specific recombination is used to integrate foreign DNA into the bacterial genome. This targeted process allows for the incorporation of specific DNA sequences at defined sites within the bacterial chromosome.

Answer 260

Site-specific recombination can also be used to integrate certain plasmids into the bacterial genome. This process facilitates the stable incorporation of plasmid DNA into the host chromosome.

Answer 261

The integration of DNA through site-specific recombination is reversible. The reverse process, known as intramolecular recombination, can occur, allowing for the removal or alteration of the integrated DNA.

Answer 262

The reversibility of site-specific recombination is crucial as it provides flexibility in genetic arrangements. It allows for the removal or reconfiguration of integrated DNA, offering a dynamic mechanism for controlling genetic changes within bacterial genomes.

Answer 263

The main repository of DNA in a bacterial cell is the chromosome. It contains the majority of the genetic information necessary for the cell's functions and characteristics.

Answer 264

In addition to the chromosome, bacterial cells may also contain plasmids. Plasmids are small, extrachromosomal DNA molecules that carry genes that can confer various traits to the bacterium.

Answer 265

The DNA in a bacterial cell contains genes, which serve as the instructions for synthesizing proteins, tRNA, rRNA, and other essential molecules. These genetic instructions dictate the structure, function, and behavior of the bacterium.

Answer 266

Each gene in bacterial DNA typically encodes a single protein, or in some cases, tRNA (transfer RNA) or rRNA (ribosomal RNA). These gene products play crucial roles in the cell's structural, transport, metabolic, and other functions.

Answer 267

Genes in bacterial DNA are categorized based on their functions, which include structural genes, transport genes, metabolic genes, and others. Each type of gene contributes to specific aspects of bacterial physiology.

Answer 268

The complement of genes in a bacterium is referred to as its genotype. This genetic makeup determines the potential traits and capabilities of the bacterium.

Answer 269

The observable properties or phenotype of a bacterial cell are determined by the expression of its genes. The interaction and regulation of these genes dictate the characteristics and behaviors that can be observed in the bacterium.

Answer 270

b) inheritance of DNA from a parent cell (normally wont change going from parent to daughter cell)

Answer 271

The bacterial chromosome is usually a single circular DNA molecule. This configuration is common in many bacterial species.

Answer 272

Bacterial DNA is packaged with proteins in a structure called the nucleoid. This region, located in the cytoplasm, organizes and compacts the DNA, ensuring efficient storage and maintenance.

Answer 273

In comparison to the E. coli chromosome (4.6 Mb), the human genome is significantly larger, with approximately 3,100 megabase pairs (Mb) in its haploid state.

Answer 274

The nucleoid is the region within the bacterial cell's cytoplasm where the chromosome is located and organized. It serves as the primary site for DNA packaging and compaction.

Answer 275

The bacterial chromosome is highly compact. Despite being approximately 500 times longer than the E. coli cell, it is efficiently organized and packaged within the nucleoid, allowing for optimal use of cellular space.

Answer 276

Bacterial chromosomes are typically single circular DNA molecules, while human chromosomes are linear and exist in pairs within the cell nucleus. This structural difference reflects the diverse nature of genetic material in different organisms.

Answer 277

The nucleoid serves the function of organizing and packaging the bacterial chromosome. It ensures that the genetic material is efficiently stored, facilitating processes such as DNA replication, transcription, and cell division.

Answer 278

DNA must be packaged within a cell to fit into the limited space of the cell's cytoplasm. Efficient packaging ensures proper organization and functioning of genetic material.

Answer 279

Nucleoid-associated proteins (NAPs) are proteins that bind to bacterial DNA, causing it to bend and fold. Their role is crucial in organizing the DNA within the nucleoid, facilitating its compact and efficient packaging.

Answer 280

Supercoiling is a process that reduces the space occupied by DNA by introducing twists and turns into the DNA molecule. This compact structure is essential for fitting the genetic material within the confines of the bacterial cell.

Answer 281

Topoisomerases enzymes play a crucial role in introducing and relieving supercoiling in DNA. They achieve this by breaking and re-ligating DNA strands, controlling the degree of twisting in the DNA molecule.

Answer 282

Supercoiling alters the physical properties of DNA by changing its helical structure. It influences the accessibility of DNA for processes such as replication, transcription, and repair, impacting the overall functionality of the genetic material.

Answer 283

Reducing the space occupied by DNA through supercoiling is essential for efficient packaging of genetic material within the cell. This compact structure allows for the optimization of cellular space and facilitates various cellular processes involving DNA.

Answer 284

Topoisomerases regulate supercoiling by introducing breaks in the DNA strands and then re-ligating them. This controlled process allows the cell to adjust the degree of supercoiling, ensuring the proper organization and functioning of the genetic material.

Answer 285

The chromosome is replicated by a complex of enzymes and proteins known as the replisome.

Answer 286

The action of helicase during replication leads to the formation of supercoils ahead of the replication fork. These supercoils need to be addressed to allow for the continued unwinding of the DNA.

Answer 287

Topoisomerase relieves supercoiling that occurs ahead of the replication fork. This enzymatic action is necessary to maintain the proper working of helicase during the unwinding of the DNA.

Answer 288

Topoisomerase is needed for helicase to continue working during replication because it relieves the supercoils that accumulate ahead of the replication fork. Without this action, helicase would be impeded in its unwinding function.

Answer 289

DNA polymerase synthesizes new DNA strands during chromosome replication. It uses the single-stranded DNA templates generated by helicase to assemble complementary nucleotides into new DNA molecules.

Answer 290

Primase is an enzyme that synthesizes short RNA primers complementary to the single-stranded DNA templates. These primers provide a starting point for DNA polymerase to initiate the synthesis of new DNA strands.

Answer 291

Chromosome replication is a coordinated process involving multiple enzymes and proteins, with helicase unwinding the DNA, topoisomerase relieving supercoiling, primase synthesizing RNA primers, and DNA polymerase synthesizing new DNA strands. The replisome is responsible for the overall coordination of these activities.

Answer 292

The replisome starts chromosome replication at the origin of replication (oriC), a specific region in the bacterial chromosome.

Answer 293

The origin of replication (oriC) in bacteria is enriched in AT base pairs and contains specific genes. It serves as the starting point for the replication of the circular bacterial chromosome.

Answer 294

The bacterial chromosome is circular in shape.

Answer 295

Chromosome replication in bacteria is bidirectional, meaning it proceeds in two directions from the origin of replication, forming two replication forks.

Answer 296

Answer: Chromosome replication in bacteria produces catenated (linked) chromosomes, meaning the newly synthesized DNA strands remain intertwined.

Answer 297

Topoisomerases form a double-stranded DNA break to separate the catenated chromosomes. They then repair the break, resulting in the formation of two separate and decatenated DNA molecules.

Answer 298

Topoisomerases play a crucial role in resolving catenated chromosomes. They induce a double-stranded DNA break to separate the linked DNA molecules, and then repair the break to generate two independent and decatenated chromosomes.

Answer 299

Bidirectional replication ensures that both ends of the circular bacterial chromosome are simultaneously replicated, allowing for the efficient and timely duplication of genetic material.

Answer 300

Topoisomerases are essential for bacterial cells because they play a critical role in DNA uncoiling and recoiling, which is necessary for various cellular processes, including DNA replication, transcription (RNA synthesis), and decatenation of chromosomes.

Answer 301

DNA uncoiling and recoiling by topoisomerases are required in cellular processes such as DNA replication and transcription (RNA synthesis).

Answer 302

Topoisomerases are involved in the decatenation of chromosomes by resolving the linked (catenated) DNA molecules formed during chromosome replication.

Answer 303

Quinolones and fluoroquinolones are broad-spectrum antibiotics that target bacterial topoisomerases. They interfere with the normal functioning of topoisomerases, disrupting DNA replication and leading to bacterial cell death.

Answer 304

Quinolones and fluoroquinolones are broad-spectrum antibiotics that target bacterial topoisomerases. Their ability to disrupt DNA replication makes them effective in treating a wide range of bacterial infections.

Answer 305

Quinolones and fluoroquinolones impact bacterial cells by interfering with the activity of topoisomerases. This interference disrupts DNA replication and other essential cellular processes, leading to bacterial cell death.

Answer 306

Quinolones and fluoroquinolones are considered broad-spectrum antibiotics because they are effective against a wide range of bacteria. Their ability to target bacterial topoisomerases makes them useful in treating diverse bacterial infections.

Answer 307

The initial step in the mechanism of topoisomerase action involves the enzyme binding to DNA and forming a double-strand break in the DNA.

Answer 308

Quinolones bind to the topoisomerase:DNA complex. This interaction interferes with the normal function of topoisomerase and has significant implications for DNA replication, transcription, and other cellular processes.

Answer 309

Quinolones binding to the topoisomerase:DNA complex blocks essential cellular processes, including DNA replication and transcription. This interference leads to the inhibition of bacterial cell growth and, ultimately, cell death.

Answer 310

A higher dose of quinolones can lead to chromosome fragmentation and the formation of reactive oxygen species in bacterial cells. These effects contribute to increased damage and further compromise bacterial viability.

Answer 311

Blocking DNA replication and transcription by quinolones disrupts crucial cellular processes, hindering bacterial growth and survival. This interference is a key aspect of their antibiotic activity against a wide range of bacteria.

Answer 312

The formation of reactive oxygen species due to quinolone treatment can contribute to additional damage and stress within bacterial cells, further enhancing the antibiotic effect and promoting bacterial cell death.

Answer 313

The quinolone mechanism is effective in treating bacterial infections because it targets a fundamental process, DNA replication and transcription, essential for bacterial growth and survival. This broad-spectrum approach makes quinolones effective against a variety of bacterial species.

Answer 314

Mobile Genetic Elements (MGEs) are genetic materials that have the ability to be transferred between cells or move within a cell. They play a significant role in contributing to genetic variability within populations.

Answer 315

Mobile Genetic Elements (MGEs) are classified based on how they replicate and how they move between or within cells.

Answer 316

Mobile Genetic Elements (MGEs) contribute to genetic variability by facilitating the transfer of genetic material between cells or movement within a cell. This diversity is crucial for adaptation and evolution in microbial populations.

Answer 317

Types of Mobile Genetic Elements (MGEs) include: 1. Plasmids 2. Transposable elements 3. Genomic islands

Answer 318

Mobile Genetic Elements (MGEs) are classified based on how they replicate (e.g., plasmids replicate independently) and how they move between or within cells (e.g., transposable elements move within the genome).

Answer 319

Plasmids are Mobile Genetic Elements (MGEs) that can replicate independently and are often involved in carrying and transferring specific genetic traits between bacterial cells.

Answer 320

Transposable elements are Mobile Genetic Elements (MGEs) that can move within a genome, changing their position and potentially influencing gene expression and function.

Answer 321

Genomic islands are Mobile Genetic Elements (MGEs) that are large segments of DNA with unique characteristics. They are often acquired through horizontal gene transfer and may carry genes that provide specific advantages to the host organism.

Answer 322

Quinolones inhibit topoisomerase activity by preventing the religation of DNA strands, leading to the accumulation of double-stranded breaks. This interference with essential cellular processes, such as DNA replication and transcription, results in the slow death of the bacterial cell.

Answer 323

Plasmids replicate independently from the bacterial chromosome.

Answer 324

An example of a replication mechanism for plasmids is rolling-circle replication.

Answer 325

Multiple copies of a plasmid are usually found in a bacterial cell.

Answer 326

The abundance of plasmids in bacterial cells is classified based on copy number. Low-copy plasmids typically have 1 to 2 copies per cell, while high-copy plasmids can have 30 to more than 100 copies per cell.

Answer 327

Components of a plasmid can be represented on a plasmid map, where genes are depicted by arrows. The length of the arrow corresponds to the size of the gene, and the direction indicates which DNA strand (coding/non-coding) encodes the gene.

Answer 328

Essential components for plasmid replication and transfer include the origin of replication (ori), which is the region where DNA synthesis begins. This region may encode proteins that initiate replication, such as by nicking the DNA, and can influence the copy number of the plasmid.

Answer 329

Essential regions in a plasmid determine its host range, indicating which species can replicate the plasmid. A narrow host range implies replication in closely related species, and such plasmids are highly reliant on host proteins.

Answer 330

A narrow host range plasmid is replicated in closely related species and is very reliant on host proteins. In contrast, a broad host range plasmid can replicate in many different species, utilizes multiple origins of replication (different in each species), and is less reliant on the host bacterial cell.

Answer 331

Plasmids with a narrow host range are replicated in closely related species, and they rely heavily on host proteins. These plasmids encode fewer proteins for replication and transfer.

Answer 332

A broad host range plasmid achieves replication in various species by having multiple origins of replication. Different species use different origins, and this allows the plasmid to replicate in a wide range of hosts.

Answer 333

A narrow host range plasmid is highly reliant on host proteins because it is designed to replicate in closely related species. The plasmid carries fewer encoded proteins for replication and transfer, making it dependent on the host's cellular machinery.

Answer 334

Accessory genes in plasmids are non-essential but often beneficial genes that may carry traits such as antibiotic resistance (e.g., amp, tet) or other functionalities.

Answer 335

Antibiotic resistance genes, such as amp and tet, are examples of accessory genes commonly found in plasmids.

Answer 336

Plasmids are classified based on the type of accessory genes they carry. For example, resistance plasmids carry genes conferring antibiotic resistance, while virulence plasmids carry genes associated with the virulence of the host bacterium.

Answer 337

In biotechnology, plasmids can be modified to carry accessory genes of interest, such as those encoding useful enzymes or therapeutics (e.g., insulin). Lab-engineered bacteria with modified plasmids are then employed to produce large quantities of specific products.

Answer 338

In biotechnology, adding accessory genes to plasmids allows the incorporation of desired traits, enabling the production of specific products such as useful enzymes or therapeutics (e.g., insulin). Lab bacteria with engineered plasmids are then used to efficiently produce these products in large quantities.

Answer 339

Resistance plasmids are a type of plasmid that carries genes conferring protection against antibiotics and heavy metals. They can harbor multiple resistance genes and often have a broad host range, making them capable of spreading easily among bacterial populations.

Answer 340

The primary function of resistance plasmids is to provide protection to bacteria against antibiotics and heavy metals by carrying and expressing resistance genes.

Answer 341

Resistance plasmids often have a broad host range, meaning they can replicate and spread easily across various bacterial species.

Answer 342

Resistance plasmids contribute to the spread of antibiotic resistance by carrying multiple resistance genes and having a broad host range. This allows them to easily transfer between different bacterial species, facilitating the dissemination of antibiotic resistance traits.

Answer 343

Resistance plasmids are of concern in the context of antibiotic resistance because they can carry and disseminate multiple resistance genes, promoting the widespread distribution of antibiotic resistance traits among bacterial populations.

Answer 344

The presence of multiple antibiotic resistance genes in a plasmid is concerning because it significantly reduces the effectiveness of antibiotics. Bacteria carrying such plasmids are resistant to multiple classes of antibiotics, making it challenging to treat infections caused by these bacteria.

Answer 345

Virulence plasmids play a crucial role in bacterial infections by carrying genes for virulence factors that contribute to the pathogenicity of bacteria, enhancing their ability to cause disease.

Answer 346

Understanding virulence plasmids in bacterial pathogens is significant as it provides insights into the mechanisms by which bacteria cause disease. This knowledge is crucial for developing strategies to prevent and treat infections caused by these bacteria.

Answer 347

Bacteria transfer some plasmids between cells through a process called conjugation.

Answer 348

Conjugative plasmids possess sex pilus genes and mobility (MOB) genes.

Answer 349

Sex pilus genes in conjugative plasmids facilitate the formation of a bridge between bacterial cells.

Answer 350

Mobility (MOB) genes in conjugative plasmids encode proteins that deliver the plasmid to the sex pilus, initiating the transfer process between bacterial cells.

Answer 351

The sex pilus forms a bridge between bacterial cells, allowing for the transfer of the plasmid from one cell to another during conjugation.

Answer 352

MOB genes encode proteins that deliver the plasmid to the sex pilus, initiating the transfer process between bacterial cells during conjugation.

Answer 353

The sex pilus attaches to the recipient cell, and mobility proteins deliver the plasmid to the base of the pilus. Plasmid replication begins, and a strand of plasmid DNA is transferred through the pilus to the recipient cell.

Answer 354

A mobilizable plasmid lacks sex pilus genes but can still be transferred. It carries MOB genes and can utilize sex pili made by other (conjugative) mobile genetic elements for transfer.

Answer 355

MOB genes in mobilizable plasmids are responsible for facilitating their transfer. Although mobilizable plasmids lack sex pilus genes, they carry MOB genes that enable them to utilize sex pili made by other conjugative mobile genetic elements for transfer.

Answer 356

Mobilizable plasmids can be transferred in the absence of sex pilus genes by utilizing sex pili made by other conjugative mobile genetic elements. The MOB genes in mobilizable plasmids play a crucial role in this transfer process.

Answer 357

Mobilizable plasmids are significant in bacterial gene transfer as they lack sex pilus genes but can still be transferred, utilizing MOB genes to utilize sex pili made by other conjugative mobile genetic elements. This mechanism expands the potential for genetic exchange among bacterial cells.

Answer 358

Transposable elements (TEs) are nucleic acid sequences that have the ability to move within or between DNA molecules, a process known as transposition.

Answer 359

Transposable elements can move within the chromosome, from the chromosome to a plasmid, and vice versa.

Answer 360

There are different mechanisms of transposition, including: 1. Simple transposition (cut and paste) 2. Replicative transposition (copy and paste)

Answer 361

Simple transposition, also known as "cut and paste," involves the direct movement of a transposable element from one location to another within the DNA, without creating a copy

Answer 362

Replicative transposition, also known as "copy and paste," involves the creation of a copy of the transposable element, which is then inserted into a new location. This process results in the presence of both the original and the copied element in the DNA.

Answer 363

Transposable elements contribute to genetic diversity in bacteria by moving within or between DNA molecules. This movement can lead to the rearrangement of genetic material and the introduction of new sequences, influencing the genetic makeup of bacterial populations.

Answer 364

An Insertion Sequence (IS) is the simplest type of transposable element, containing only the elements necessary for transposition. It typically includes a gene encoding transposase and inverted repeat (IR) sequences at both ends, serving as recognition sites for transposase.

Answer 365

The main characteristic of an Insertion Sequence (IS) is its simplicity, as it only contains the essential elements needed for transposition.

Answer 366

The gene encoding transposase in an Insertion Sequence (IS) is responsible for catalyzing the transposition process, facilitating the movement of the element within the genome.

Answer 367

Inverted repeat (IR) sequences are found at both ends of an Insertion Sequence (IS), serving as recognition sites for the transposase enzyme.

Answer 368

An Insertion Sequence (IS) is flanked by direct repeats (DRs), which result from the transposition process. These repeats can be important for identifying the location where the IS was inserted in the genome.

Answer 369

In simple transposition, the transposable element (TE) produces transposase, a crucial enzyme for the transposition process.

Answer 370

Transposase, produced by the transposable element (TE), cuts the DNA at the inverted repeats (IRs), facilitating the excision of the TE from the DNA during simple transposition.

Answer 371

The action of transposase during simple transposition results in the excision of the transposable element (TE) from the DNA, forming a "mobile" complex of transposase and the TE.

Answer 372

In simple transposition, transposase cuts the DNA at the inverted repeats (IRs), which serve as recognition sites for the enzyme. This cutting action allows the transposable element (TE) to be excised from the DNA.

Answer 373

The "mobile" complex formed of transposase and the transposable element (TE) represents the active, mobile form of the TE. This complex is capable of transposing to new locations within the genome or being transferred to other DNA molecules.

Answer 374

In simple transposition, transposase, produced by the transposable element (TE), cuts the DNA at inverted repeats (IRs), leading to the excision of the TE from the DNA. This process results in the formation of a "mobile" complex capable of moving within or between DNA molecules.

Answer 375

1. Target DNA is cut, creating an insertion site. 2. Transposase facilitates the insertion of transposable element (TE) DNA into the cut target DNA. 3. DNA flanking the insertion site is filled in and repaired. 4. The repair process generates direct repeats (DRs) flanking the inserted TE at the insertion site.

Answer 376

The insertion site is where the transposable element (TE) is integrated into the target DNA during simple transposition. This process creates a site of genetic modification.

Answer 377

Transposase is essential in simple transposition as it catalyzes the cutting of DNA at inverted repeats, facilitates the movement of the transposable element (TE), and enables its insertion into the target DNA.

Answer 378

The repair process is crucial in simple transposition as it completes the integration of the transposable element (TE) into the target DNA. It fills in and repairs the DNA flanking the insertion site, generating direct repeats (DRs) that serve as markers of the insertion event.

Answer 379

The repair-generated direct repeats (DRs) are important markers that flank the inserted transposable element (TE) and provide insight into the location where the TE was integrated into the target DNA during simple transposition.

Answer 380

Some transposable elements (TEs) may have additional components, such as unit transposons.

Answer 381

A unit transposon is a type of transposable element (TE) that includes a transposase gene and inverted repeats at both ends.

Answer 382

Within a unit transposon, there may be accessory genes located between the inverted repeats. These accessory genes can include elements like antibiotic resistance genes.

Answer 383

Accessory genes within a unit transposon, such as antibiotic resistance genes, confer additional traits to the host organism. For example, they may provide resistance to specific antibiotics.

Answer 384

In addition to accessory genes, a unit transposon may contain other genes involved in transposition, such as resolvases. These genes contribute to the movement and stability of the transposable element.

Answer 385

answer on onq

Answer 386

TE insertion can impact gene function and regulation in various ways, such as inactivating a gene when inserted into it or changing transcription when inserted next to a gene.

Answer 387

TE insertion into a gene can result in the inactivation of that gene, potentially leading to loss of its function.

Answer 388

TE insertion next to a gene can alter transcription, influencing the regulation of that gene and potentially changing its expression level.

Answer 389

TEs can take flanking DNA during transposition, allowing them to spread to other bacteria. This contributes to the horizontal transfer of genetic material.

Answer 390

A genomic island is a region of the chromosome that has been acquired through horizontal gene transfer (HGT). It typically ranges in size from 10 to over 600 kilobases (kb).

Answer 391

Conjugative genomic islands are genomic islands that encode functions for excision, conjugation, and integration. They are capable of transferring themselves from one bacterial cell to another.

Answer 392

Mobilizable genomic islands encode functions for excision and integration but lack the ability for self-transfer. They require the presence of a conjugative mobile genetic element (MGE) for transfer.

Answer 393

Conjugative genomic islands encode the necessary machinery for conjugation, including excision, conjugation, and integration functions, allowing them to transfer autonomously from one bacterial cell to another.

Answer 394

Genomic islands contribute to genetic diversity by mobilizing and transferring flanking DNA. They usually contain genes that improve the fitness of the bacterial host.

Answer 395

Some genomic islands contribute to bacterial pathogenicity by carrying virulence factor genes. These genes can transform otherwise harmless bacteria into pathogens.

Answer 396

Virulence factor genes carried by genomic islands play a key role in bacterial pathogenicity by providing the bacteria with traits that enhance their ability to cause disease.

Answer 397

An example is the Salmonella Pathogenicity Island 1, which contributes to the pathogenicity of Salmonella by encoding a type III secretion system and other virulence factors. allows Salmonella to inject proteins into host cells. This contributes to the bacteria's ability to invade intestinal cells, causing inflammation and diarrhea.

Answer 398

The presence of pathogenicity islands can significantly impact the virulence of a bacterium by introducing virulence factor genes that enhance the bacterium's ability to cause disease. This genetic contribution can turn initially non-pathogenic bacteria into pathogens.

Answer 399

a) F+ regular F factor cell is F+

Answer 400

Conjugation is the direct transfer of DNA between bacterial cells. This process involves cells connected by a structure known as a sex pilus, through which genetic material is transferred.

Answer 401

The sex pilus is a structure that connects bacterial cells during conjugation, facilitating the direct transfer of genetic material from one cell to another.

Answer 402

Conjugation requires the presence of conjugative mobile genetic elements (MGEs) within bacterial cells. These elements carry genes necessary for the formation of the sex pilus and other functions related to the transfer of DNA.

Answer 403

Conjugative mobile genetic elements (MGEs) typically carry genes involved in the formation of the sex pilus, as well as MOB (mobilization) genes and other elements required for DNA transfer.

Answer 404

An example is the F factor found in E. coli, which plays a crucial role in conjugation by carrying sex pilus genes, MOB genes, and other elements necessary for the transfer of genetic material.

Answer 405

The F factor in E. coli contributes to conjugation by carrying essential genes, including those for the sex pilus and MOB genes, enabling the direct transfer of DNA between bacterial cells.

Answer 406

Conjugation is significant in bacterial genetics as it allows for the direct transfer of genetic material between cells, facilitating the exchange of traits such as antibiotic resistance and contributing to genetic diversity.

Answer 407

Donor: The donor cell is F+ (carrying the F factor). Recipient: The recipient cell is F- (lacks the F factor). Attachment: The sex pilus of the F+ donor attaches to the F- recipient. Pilus Retraction: The pilus retracts, bringing the donor and recipient cells into close proximity. Type IV Secretion System (T4SS): The pilus converts into a type IV secretion system (T4SS), facilitating the direct transfer of DNA from the donor to the recipient.

Answer 408

The sex pilus in F factor-mediated conjugation serves as the structure that facilitates the attachment of the F+ donor cell to the F- recipient cell, allowing for the subsequent transfer of genetic material.

Answer 409

After the sex pilus retracts, the pilus undergoes a conversion to a type IV secretion system (T4SS), enabling the direct transfer of DNA from the F+ donor cell to the F- recipient cell.

Answer 410

F factor-mediated conjugation is significant as it allows for the rapid transfer of genetic material, including the F factor itself, between bacterial cells. This contributes to the spread of traits such as antibiotic resistance and genetic diversity in bacterial populations.

Answer 411

The process of conjugation requires that a bacterial cell contains a conjugative mobile genetic element like the F factor plasmid - conjugative plasmids like the F factor carry genes that encode for the proteins that make up the sex pilus, as well as the mobility (or mob) genes. A bacterial cell that carries the F factor plasmid is said to be F+. So, if we have F+ x F- mating, a cell that is carrying the F factor is transferring a copy of the F factor to a bacterial cell that did not originally have an F factor (or, in other words, a cell that is F-). F- cells (which lack an F factor) don’t have the necessary genes to produce a sex pilus, nor do they have an F factor plasmid that could be transferred through the sex pilus. With this in mind, F- x F- mating is something that can’t really occur: neither cell can produce the proteins that are needed for conjugation to occur.

Answer 412

The F factor in conjugation, particularly in F+ × F- mating, contains the origin of transfer (oriT). This region is crucial for the initiation of DNA transfer from the donor to the recipient.

Answer 413

Both the F factor and mobilizable plasmids share the presence of the origin of transfer (oriT), a region essential for initiating the transfer of DNA.

Answer 414

The relaxosome, which includes a relaxase enzyme, cuts the DNA at the oriT (origin of transfer) of the F factor. This process is crucial for initiating the transfer of genetic material during conjugation.

Answer 415

After the relaxosome cuts the DNA at oriT, the intact strand undergoes rolling-circle replication. This process results in the synthesis of a complementary strand, generating the DNA molecule that will be transferred to the recipient cell.

Answer 416

The coupling factor, which recognizes the cut DNA bound to the relaxase (part of the relaxosome), plays a crucial role in delivering the DNA to the type IV secretion system (T4SS) for transfer to the recipient cell.

Answer 417

The coupling factor is significant in F factor-mediated conjugation as it recognizes the cut DNA bound to the relaxase and facilitates the delivery of the DNA to the type IV secretion system (T4SS) for transfer to the recipient cell.

Answer 418

Rolling-circle replication generates the complementary strand of DNA, ensuring the transfer of the intact strand to the recipient cell. This process is essential for the successful transfer of genetic material during conjugation.

Answer 419

The type IV secretion system (T4SS) pumps the cut F factor strand and the relaxase enzyme into the recipient cell, facilitating the transfer of genetic material from the donor to the recipient.

Answer 420

The cut strand is replicated within the recipient cell, forming an intact F factor. This results in the conversion of the recipient cell to an F+ cell.

Answer 421

What is the outcome for the recipient cell after the successful transfer of genetic material in F factor-mediated conjugation?

Answer 422

In F- × F- mating, the F factor is transferred from the donor to the recipient, converting the recipient into an F+ cell. In F+ × F- mating, other genetic material is transferred, and the recipient remains F- but gains specific genetic traits.

Answer 423

The successful transfer of the F factor in conjugation is significant as it results in the conversion of the recipient cell to an F+ cell. This not only increases the prevalence of the F factor in bacterial populations but also allows the newly converted F+ cell to participate as a donor in subsequent conjugation events.

Answer 424

F factor-mediated conjugation facilitates the spread of genetic material by converting F- cells to F+ cells, enabling them to act as donors in further conjugation events. This process contributes to the dissemination of traits, including antibiotic resistance, in bacterial populations.

Answer 425

The F factor can integrate into the bacterial chromosome, resulting in the formation of an Hfr cell (high frequency of recombination).

Answer 426

An Hfr cell, or high frequency of recombination cell, is a bacterial cell in which the F factor has integrated into the chromosome. This integration increases the likelihood of recombination events during conjugation.

Answer 427

Yes, conjugation can still occur in an Hfr cell after the integration of the F factor into the chromosome. The cell retains the ability to transfer genetic material to a recipient cell.

Answer 428

During conjugation in an Hfr cell, the relaxosome nicks the oriT (origin of transfer), and the DNA is delivered to the type IV secretion system (T4SS). Some chromosomal DNA, along with the F factor, is transferred to the recipient cell.

Answer 429

In an Hfr cell, conjugation involves the transfer of both the F factor and some chromosomal DNA. This can lead to the introduction of specific chromosomal genes into the recipient cell.

Answer 430

Hfr cells are significant in bacterial genetics as they can transfer not only the F factor but also portions of the bacterial chromosome during conjugation. This contributes to the exchange of chromosomal genes and genetic diversity among bacterial populations.

Answer 431

The integration of the F factor into the chromosome increases the recombination frequency during conjugation in Hfr cells, as chromosomal DNA is more likely to be transferred along with the F factor to the recipient cell.

Answer 432

Yes, the integration of the F factor into the bacterial chromosome is reversible, and errors can occur during the excision process.

Answer 433

Errors can occur during the excision of the F factor, leading to the incorporation of extra DNA. This process can result in the formation of an F' plasmid.

Answer 434

Answer: An F' plasmid is formed when the F factor excises from the bacterial chromosome, taking along additional chromosomal DNA. This plasmid carries the extra genetic material.

Answer 435

In F' × F- mating, the recipient cell receives an F' plasmid. This plasmid carries not only the F factor but also additional chromosomal DNA.

Answer 436

In F' × F- mating, the recipient cell gains an F' plasmid, which contains both the F factor and additional chromosomal DNA. This genetic material can confer new traits to the recipient.

Answer 437

The formation of F' plasmids, through errors during the excision of the F factor, contributes to genetic variability by carrying additional chromosomal DNA. This variability can be transferred to recipient cells during conjugation.

Answer 438

Reversible F factor integration and the formation of F' plasmids contribute to genetic diversity in bacterial populations by allowing the exchange of chromosomal DNA during conjugation. This process introduces novel traits and variability among bacterial cells.

Answer 439

F' plasmid-mediated conjugation involves the transfer of an F' plasmid, which carries both the F factor and additional chromosomal DNA. This is in contrast to traditional F factor-mediated conjugation, where only the F factor is transferred.

Answer 440

Bacterial transformation is the process by which bacteria acquire DNA from their environment. Unlike conjugation, which involves direct cell-to-cell transfer, transformed DNA can be integrated into the bacterial genome, degraded, or replicated as plasmids.

Answer 441

Bacteria undergo transformation for various reasons, including: 1. Genetic Diversity: To introduce new genetic material and increase diversity. 2. DNA Repair: To repair damaged DNA through the incorporation of intact DNA. 3. Nutrition: Some bacteria may utilize the acquired DNA as a source of nutrients. 4. Selective Uptake: Transformation may be selective, favoring DNA from related species, which aids in recombination.

Answer 442

Bacterial transformation contributes to genetic diversity by introducing new genetic material into bacterial populations, allowing for the exchange of traits and increasing overall genetic variability.

Answer 443

: DNA from related species, when acquired through transformation, can facilitate recombination and contribute to genetic diversity. This selective uptake may enhance the adaptive capabilities of bacteria.

Answer 444

Some bacteria may use the acquired DNA as a source of nutrients, demonstrating a functional aspect of transformation beyond genetic exchange.

Answer 445

The selectivity of bacterial transformation can be influenced by factors such as the preference for DNA from related species, aiding in recombination and the acquisition of beneficial traits.

Answer 446

Bacterial transformation can confer several benefits to bacterial populations, including increased genetic diversity, DNA repair, access to nutrients, and the potential for selective uptake of DNA from related species for advantageous traits.

Answer 447

Answer: Competence refers to the state of a bacterium being able to take up extracellular DNA from its environment. Not all bacteria are naturally competent, and the ability to undergo competence may be constitutive or induced under specific conditions.

Answer 448

No, not all bacteria are naturally competent. Competence can vary among bacterial species, with some being constitutively competent, while others become competent only under specific conditions, such as certain growth phases. Factors influencing competence include cell-cell signaling, nutritional stress, and exposure to DNA-damaging agents.

Answer 449

Constitutive competence refers to the constant or continuous ability of some bacteria to take up DNA, irrespective of external conditions. In contrast, competence triggered under specific conditions occurs only in response to particular stimuli, such as certain growth phases, cell-cell signaling, nutritional stress, or exposure to DNA-damaging agents.

Answer 450

Competence in bacteria can be induced by various factors, including: 1. Cell-Cell Signaling: Communication between bacterial cells triggering the competence state. 2. Nutritional Stress: Conditions of nutrient limitation or stress. 3. DNA-Damaging Agents: Exposure to agents causing DNA damage, prompting the bacteria to enter a competent state.

Answer 451

Competence is significant in bacterial biology as it enables bacteria to take up extracellular DNA, contributing to genetic diversity. This process can facilitate genetic exchange, adaptation to environmental changes, and the acquisition of beneficial traits.

Answer 452

Competence contributes to genetic diversity by allowing bacteria to take up extracellular DNA, promoting genetic exchange, and introducing new genetic material into bacterial populations. This process enhances the adaptability and evolutionary potential of bacterial communities.

Answer 453

Competence (Com) proteins are essential for bacterial transformation. They facilitate the process by aiding in the uptake and incorporation of extracellular DNA into the bacterial genome.

Answer 454

The production of Competence (Com) proteins is regulated in bacterial cells. This regulation involves the secretion of a competence-stimulating peptide (CSP). Sufficient presence of CSP activates receptors, leading to the transcription of com genes responsible for producing Competence proteins.

Answer 455

Competence-stimulating peptide (CSP) plays a crucial role in regulating competence. It is secreted by bacterial cells, and if a sufficient amount of CSP is present, it activates receptors, leading to the transcription of com genes responsible for the production of Competence proteins.

Answer 456

The presence of competence-stimulating peptide (CSP) ensures the activation of com genes by activating receptors when a sufficient amount of CSP is present. This activation triggers the transcription of com genes, facilitating the production of Competence proteins.

Answer 457

The regulation of competence, involving the production of Competence proteins in response to competence-stimulating peptide (CSP), ensures that bacterial cells become competent for transformation when necessary. This regulatory mechanism allows bacteria to take up extracellular DNA, promoting genetic exchange and diversity.

Answer 458

Lac+ cells can metabolize lactose whereas Lac- cannot

Answer 459

Some bacteria, such as E. coli, are not naturally competent, meaning they cannot naturally take up extracellular DNA. However, in the laboratory, these bacteria can be made competent through artificial means, enabling them to undergo transformation.

Answer 460

Chemically competent cells are bacteria, like E. coli, that are treated with calcium chloride in the laboratory to become competent for transformation. Calcium ions inactivate the negative charge on DNA, and a subsequent heat shock increases cell permeability, allowing DNA to enter the cell.

Answer 461

Electrocompetent cells are bacterial cells that are made competent for transformation using electrical current. The application of electrical current forms pores in the cell membrane, allowing DNA to enter the cell.

Answer 462

Artificial competence is significant in the laboratory as it enables bacteria, like E. coli, which are not naturally competent, to take up extracellular DNA. This process is essential for genetic engineering, molecular biology, and various biotechnological applications.

Answer 463

Bacteriophages carry genetic material in their capsid, which is the protein coat or protective shell surrounding the viral nucleic acids.

Answer 464

Phages transfer DNA to bacteria through a process called transduction. Phages that mediate this transfer are referred to as transducing particles.

Answer 465

The transduction process mediated by bacteriophages is significant in bacterial genetics as it enables the transfer of genetic material between bacteria. This contributes to genetic diversity and the spread of traits within bacterial populations.

Answer 466

In the lytic cycle, the bacteriophage immediately replicates within the host cell, leading to the lysis or rupture of the host cell, releasing newly formed viral particles.

Answer 467

In the lysogenic cycle, the viral genome integrates into the bacterial chromosome. The bacterium becomes a lysogen, containing a prophage. The phage can reemerge under certain conditions.

Answer 468

In the context of bacteriophage replication, a lysogen is a bacterium that contains a prophage—viral genetic material integrated into its chromosome during the lysogenic cycle.

Answer 469

The prophage can reemerge from a lysogen in the lysogenic cycle under certain conditions, triggering the transition to the lytic cycle. These conditions may include stress or environmental factors that prompt the activation of the prophage.

Answer 470

The lytic cycle contributes to the replication of bacteriophages by immediately replicating the viral genome within the host cell and subsequently causing the lysis of the host cell, releasing newly formed viral particles.

Answer 471

The lysogenic cycle is significant in the life cycle of bacteriophages as it allows the viral genome to integrate into the bacterial chromosome, leading to a dormant state. This integration facilitates the persistence of the viral genetic material within the host bacterial population.

Answer 472

In the context of bacteriophage replication cycles, a prophage is the integrated form of viral genetic material within the bacterial chromosome during the lysogenic cycle.

Answer 473

The initial step in the lytic cycle of bacteriophage replication is the adsorption of the phage to the surface of the host cell. This adsorption is facilitated by specific receptors on the bacterial cell surface.

Answer 474

Following the adsorption of the phage to the bacterial cell in the lytic cycle, the phage injects its DNA into the cell, while the capsid (protein coat) of the phage remains outside the cell.

Answer 475

After injection into the bacterial cell during the lytic cycle, phage DNA directs the degradation of the host DNA and initiates the replication of the phage DNA.

Answer 476

The ultimate outcome of the lytic cycle in bacteriophage replication is the lysis or rupture of the host bacterial cell, releasing newly formed viral particles into the surrounding environment.

Answer 477

In the lytic cycle, phage DNA directs the degradation of host DNA and the replication of phage DNA, facilitating the production of new viral particles and ultimately leading to the lysis of the host bacterial cell.

Answer 478

In the lytic cycle, phage DNA directs the host bacterial cell to synthesize phage proteins, including those composing the capsid of the viral particles.

Answer 479

During the lytic cycle, phage DNA is packaged into newly synthesized capsids, which are protein coats that encapsulate the viral genetic material.

Answer 480

In the lytic cycle, new phage particles are assembled as phage DNA is packaged into capsids, and other phage proteins, such as the capsid proteins, are synthesized. This assembly process occurs within the host bacterial cell.

Answer 481

The overall outcome of the lytic cycle in bacteriophage replication is the production of multiple new phage particles within the host bacterial cell, followed by the lysis of the cell and the release of these phage particles into the surrounding environment.

Answer 482

During the lytic cycle, bacterial DNA can be randomly packaged into the capsid along with phage DNA. This process results in the formation of a transducing particle containing both phage DNA and bacterial DNA.

Answer 483

The process where bacterial DNA is randomly packaged into the capsid during the lytic cycle is known as generalized transduction.

Answer 484

Generalized transduction contributes to the genetic diversity of bacterial populations by facilitating the transfer of bacterial genes between bacteria during the lytic cycle of bacteriophage replication. This process introduces new genetic material into bacterial populations.

Answer 485

In generalized transduction, a transducing particle serves as a vehicle for the transfer of genetic material between bacteria by injecting its DNA into a new bacterial cell.

Answer 486

Unlike the lytic cycle, the injection of DNA by a transducing particle during generalized transduction is not lytic, meaning it does not involve the injection of phage DNA. Instead, the transducing particle injects a mixture of phage DNA and bacterial DNA into the new cell.

Answer 487

The injected DNA, which includes both phage DNA and randomly packaged bacterial DNA, can integrate into the chromosome of the new bacterial cell. This integration contributes to the potential genetic modification of the recipient bacterial cell.

Answer 488

Generalized transduction is considered non-lytic because it involves the injection of a transducing particle's DNA into a new bacterial cell without causing the lysis or rupture of the new cell.

Answer 489

Generalized transduction differs from the lytic cycle in terms of DNA transfer because it involves the transfer of a mixture of phage DNA and bacterial DNA by a transducing particle, leading to potential genetic changes in the recipient bacterial cell.

Answer 490

The injection of DNA by a transducing particle, which can contain randomly packaged bacterial DNA, contributes to the genetic diversity of bacterial populations by introducing new genetic material into recipient bacterial cells during generalized transduction.

Answer 491

Lysogeny refers to a state in which the viral genome is maintained in a bacterial cell without immediately initiating the lytic cycle. During lysogeny, lytic genes of the phage are not expressed.

Answer 492

During lysogeny, the lytic genes of the phage are not expressed. This is in contrast to the lytic cycle, where these genes are actively transcribed and translated.

Answer 493

During lysogeny, the phage genome may integrate into the bacterial chromosome, forming a prophage. This integration is a key feature of lysogeny.

Answer 494

A prophage is a phage genome that has integrated into the chromosome of a bacterial cell during lysogeny. The prophage remains dormant until certain conditions trigger its activation.

Answer 495

During lysogeny, the phage genome replicates when the bacterium replicates. This ensures the maintenance of the prophage in the bacterial cell's progeny.

Answer 496

Lysogeny may be advantageous for a phage when the abundance of the host bacterium is low. In such situations, delaying the initiation of the lytic cycle allows the phage to persist within the bacterial population.

Answer 497

Lysogeny represents a strategy by which phages interact with bacteria, allowing them to persist within the bacterial population without immediately causing cell lysis. This can be beneficial for both the phage and the host bacterium under certain conditions.

Answer 498

The process by which a prophage transitions to a lytic cycle is called induction. The key event associated with this transition is the initiation of the synthesis of phage proteins by the prophage.

Answer 499

Induction of a prophage, and the subsequent transition to the lytic cycle, can be triggered by stress to the bacterial cell. Factors such as DNA damage or antibiotic treatment are known to induce the prophage.

Answer 500

During induction, the prophage initiates the synthesis of phage proteins. The phage genome is then excised from the bacterial chromosome, replicated, and new phages are assembled. Eventually, the bacterial cell is lysed, releasing the newly formed phages.

Answer 501

Stress to the bacterial cell, such as DNA damage or exposure to antibiotics, can induce a prophage and lead to the initiation of the lytic cycle.

Answer 502

The induction of a prophage is important because it marks the transition to the lytic cycle, where the phage actively replicates and lyses the bacterial cell. The urgency is associated with the need for the phage to propagate and complete its life cycle before adverse conditions, such as the death of the host cell, occur.

Answer 503

Induction of a prophage allows the phage to actively replicate, produce new phages, and be released from the bacterial cell through lysis. This contributes to the survival and propagation of the phage within the bacterial population.

Answer 504

Specialized transduction differs from generalized transduction because it involves the transfer of specific, non-random DNA from the integration site of a prophage.

Answer 505

Errors during the excision of a prophage can occur, leading to the incorporation of DNA from the integration site. This results in mixed genetic material being packaged into transducing particles during specialized transduction.

Answer 506

In specialized transduction, the DNA transferred is specific and non-random. It includes DNA from the integration site of the prophage rather than random bacterial DNA.

Answer 507

Specialized transduction is significant as it allows the transfer of specific, non-random DNA from the integration site of a prophage to another bacterial cell. This targeted transfer can contribute to the exchange of specific genes among bacterial populations.

Answer 508

The DNA transferred during specialized transduction is not random because it specifically includes genetic material from the integration site of the prophage. This targeted transfer distinguishes specialized transduction from the random DNA transfer observed in generalized transduction.

Answer 509

The consequence of mixed genetic material being packaged into transducing particles is that specific DNA from the integration site of the prophage is transferred to another bacterial cell, contributing to the unique characteristics of specialized transduction.

Answer 510

Transducing particles in specialized transduction contain mixed genetic material, including DNA from the integration site of the prophage. This DNA is specific and non-random.

Answer 511

Lysogenic conversion refers to the ability of a prophage to change the phenotype of the lysogen, or bacterial host. This change often involves modifications to the cell surface, such as the removal of receptors needed for phage infection. As a result, the lysogen becomes immune to the same or similar phages.

Answer 512

Lysogenic conversion contributes to the immune response of a lysogen by modifying the cell surface, which may involve removing receptors needed for phage infection. This modification renders the lysogen immune to the same or similar phages.

Answer 513

Lysogenic conversion often involves modifications to the cell surface of the lysogen. This can include changes such as the removal of receptors that are necessary for phage infection.

Answer 514

Lysogenic conversion provides protection to the prophage DNA by making the lysogen immune to the same or similar phages. The modifications to the cell surface, such as the removal of receptors needed for phage infection, contribute to this protection.

Answer 515

A prophage may introduce genes unrelated to phage replication during lysogenic conversion. These genes could encode various traits, such as toxin production or antibiotic resistance, impacting the lysogen's phenotype beyond the ability to resist phage infection.

Answer 516

Lysogenic conversion can impact the lysogen's phenotype by introducing genes unrelated to phage replication. These genes may contribute to traits such as toxin production, antibiotic resistance, or other characteristics that modify the lysogen's phenotype.

Answer 517

Lysogenic conversion enhances the survival of the prophage within the bacterial population by providing a selective advantage to the lysogen. The modified phenotype, including immunity to certain phages and additional traits, contributes to the adaptation and persistence of the lysogen in its environment.

Answer 518

Prophages are common in pathogens and contribute to their virulence by encoding virulence factors, such as toxins. These factors can play a crucial role in the ability of bacteria to cause diseases.

Answer 519

Extracellular vesicles are spherical structures surrounded by a lipid bilayer. These vesicles are released from the surface of bacterial cells and contain cargo from the cytoplasm or periplasm, including proteins, nutrients, DNA, and other cellular components.

Answer 520

Extracellular vesicles contain a diverse cargo, including proteins, nutrients, DNA, and other cellular components. This cargo is enclosed within the lipid bilayer structure of the vesicles.

Answer 521

In gram-negative bacteria, extracellular vesicles are referred to as outer-membrane vesicles.

Answer 522

Extracellular vesicles are released from bacterial cells by being shed from the cell surface. These vesicles carry cargo from the cytoplasm or periplasm and play a role in intercellular communication and the delivery of cellular components.

Answer 523

Extracellular vesicles play a role in bacterial communication by serving as carriers of cargo between bacterial cells. The release of vesicles allows the transfer of proteins, nutrients, and other molecules, facilitating communication and interactions between bacteria.

Answer 524

Extracellular vesicles contribute to the exchange of cellular components among bacteria by carrying cargo from the cytoplasm or periplasm. The release of these vesicles allows the transfer of proteins, nutrients, DNA, and other molecules between bacterial cells.

Answer 525

Extracellular vesicles contribute to the diversity of cargo exchange between bacterial cells by encapsulating a variety of cellular components. The vesicles can carry proteins, nutrients, DNA, and other molecules, enhancing the versatility of intercellular communication and cooperation among bacteria.

Answer 526

The lipid bilayer structure of extracellular vesicles is significant as it provides a protective enclosure for the cargo they carry. This structure allows the vesicles to transport cellular components, including proteins and DNA, while protecting them from the external environment.

Answer 527

The cargo within extracellular vesicles originates from the cytoplasm or periplasm of bacterial cells. This cargo can include a range of components such as proteins, nutrients, DNA, and other cellular materials.

Answer 528

Extracellular vesicles contribute to horizontal gene transfer (HGT) by fusing with the membrane of recipient cells. The DNA cargo carried by these vesicles is then transferred into the recipient cell, facilitating the exchange of genetic material. This process can introduce genes for antibiotic resistance, virulence, and other traits into the recipient cell.

Answer 529

Extracellular vesicles transfer DNA cargo to recipient cells by fusing with the recipient cell membrane. This fusion allows the transfer of genetic material, including genes for antibiotic resistance, virulence, and other traits, contributing to horizontal gene transfer among bacteria.

Answer 530

Extracellular vesicles can transfer various types of cargo in addition to DNA. This may include proteins, enzymes, toxins, and other cellular components. The transfer of such cargo contributes to functions like antibiotic resistance and virulence in recipient cells.

Answer 531

The transfer of DNA cargo via extracellular vesicles contributes to bacterial traits like antibiotic resistance and virulence by introducing genes associated with these traits into the recipient cells. This process enhances the genetic diversity and adaptability of bacterial populations.

Answer 532

The transfer of cargo via extracellular vesicles can contribute to antibiotic resistance by introducing genes for antibiotic resistance into recipient cells. These genes may encode mechanisms that help bacteria withstand the effects of antibiotics.

Answer 533

The transfer of cargo via extracellular vesicles can influence various bacterial traits, including virulence. Genes associated with virulence factors may be transferred, contributing to the pathogenicity of recipient cells

Answer 534

Extracellular vesicles have the potential to significantly impact the spread of antibiotic resistance and virulence among bacteria by facilitating the transfer of genetic material, including genes for these traits, between bacterial cells.

Answer 535

The fusion of extracellular vesicles with recipient cell membranes contributes to genetic diversity in bacterial populations by facilitating the horizontal transfer of genes. This process introduces new genetic material, including genes for antibiotic resistance and virulence, into the recipient cells, enhancing the overall genetic diversity of bacterial populations.

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