Lecture Quiz #1 Flashcards
Bacteria are ________, whereas fungi, protozoa, parasites are _________.
prokaryotes; eukaryotes
What structures and organelles do bacteria have?
- Bacteria do not have internal membrane-bound organelles
- Bacteria have no sophisticated internal structures: no nuclear membrane, no mitochondria, no Golgi, no endoplasmic reticulum
List and describe the 6 common shapes of bacteria
Cocci: round Coccobacilli: two cocci attached to each other Curved: horseshoe shaped Diplococci: two cocci next to each other Bacilli: rod-shaped Spiral: wavy-shaped
Define morphology
The form and structure of an organism or group of identical organisms
What do you need to know about a bacteria cell to identify its morphology?
What stage of growth a bacteria is in
Patterns of groups of identical bacteria are reflective of what?
cell division/ binary fission
Define pleomorphic
Each cell of a species has a slightly different shape when it divides
Describe aggregation properties
- Determined by the orientation of the cell division plane to the axis of the cell and the tendency of progeny cells to adhere to one another
- Can be characteristic of a species
What functions do structures from the cytoplasmic (inner) membrane and outward perform?
1) Protection from the external environment (includes host defense)
2) Permeability barrier for selective transport of nutrients and information
3) Control over physical location (ex: through flagella)
What does an environment primarily see first about a bacteria? Why?
Structures, because they are both external and unique (or foreign)
What do bacterial structures allow for humans to do?
Structures are often important antigens, so they can be used as vaccine targets and in diagnostics and epidemiology
Bacterial structures and their composition often reflect what?
Adaptations to the environment
Cell surface _______ can be targets for antibiotics
Cell surface _______ can be a barrier to antibiotics
structures; properties
What do bacterial cells use external structures for?
1) Cell surface structures often used to attach to and invade host cells and “sense” their environment to appropriately express virulence factors
2) Certain structures are not necessarily essential for viability, but are often important in pathogenesis as virulence factors
True or false: Structures are not expressed at all times and may be lost during continuous culture in laboratory media
True
Define peptidoglycan (murein)
One of the key components of bacteria that makes up cell wall and is the basis for a Gram stain reaction
The cell membrane of a bacteria is called the _______ membrane
cytosolic
List the 4 characteristics of peptidoglycan
1) Key contributor in overall shape of bacteria
2) Crucial for osmotic stability
3) Unique structure found only in bacteria
4) Makes a good target for antimicrobial agents (since it’s unique to bacteria and crucial to their survival)
Define lipopolysaccharide
An endotoxic structure found in the outer membrane (of the cytosolic membrane) of gram-negative bacteria.
How can you tell lipoteichoic acid and teichoic acid apart?
Lipoteichoic acid has a connection down to the cell membrane, whereas teichoic acid is only on the surface of the cell wall.
Lipoteichoic acids and teichoic acids are only found in gram-_______ bacteria
positive
Describe the characteristics of a gram-negative cell envelope
1) Inner membrane: symmetrical bilayer of phospholipids
2) Periplasm: sandwiched between IM and OM / gel-like matrix
3) Outer membrane: asymmetrical bilayer of lipids; serves as a selective permeability barrier that is virtually impermeable to hydrophilic solutes
4) Phospholipids in the inner leaflet and LPS in outer leaflet
How does the difference between gram-positive and gram-negative bacteria affect treatment plans for patients?
Since gram-negative bacteria’s outer membranes are virtually impenetrable to hydrophilic solutes, it affects which antibiotics are used in treatment
Define porins
Channel-forming proteins for the purpose of allowing
influx of nutrients and extrusion of waste products
True or false: The fluid mosaic model applies to the lipid bilayer of bacteria
True
Define a phospholipid
Has a head group and long hydrophobic fatty acid chains
Describe the importance of phospholipids to bacteria
- There’s a lot of diversity in just phospholipids; there are numerous fatty acids that can make up the fatty acid chains.
- Can vary in saturation (triple bonds, double bonds, single bonds, etc), length, cis/trans bond confirmations, isomerase, branched fatty acids, anteiso, and modification with OH groups
- Aids in membrane homeostasis (particularly with environmental changes like pH, salinity, oxygen, pressure, temperature, etc)
If a bacteria needed to change an element of itself to avoid lyseing due to environmental changes, what element would that be?
The fatty acids of phospholipids
Define a cell wall and describe where they can and can’t be found
- Defined as a semirigid structure surrounding the cytoplasmic membrane enabling the cell to resist bursting from osmotic pressure
- Found only in true Eubacteria, not found in Mycoplasmas
True or false: the cell membranes of bacteria are porous
True, so nutrients/ metabolites can actively diffuse to the plasma membrane
What is the main component of a bacteria’s cell wall?
Peptidoglycan (murein)
Describe what peptidoglycan (murein) is composed of
- Consist of a polymer of sugars and amino acids that forms a mesh-like layer located outside the cytoplasmic membrane
- Carbohydrate portion consists of alternating residues of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
- A peptide chain (3-5 amino acids) is attached to N-acetylmuramic acid
- Contains cross-linking bridges
How does the peptidoglycan of bacterial cell walls undergo degredation?
Undergoes degradation and remodeling through autolysins that introduce controlled breaks for growth/division
Describe the importance of peptidoglycans for immune response
- Peptidoglycan is conserved microbial structure that is immunogenic; recognized by the Nod proteins (innate immune response)
- Bacteria incorporate D-amino acids (unlike humans’ L-amino acids), so we know to attack it
Peptidases only recognize the ______ of amino acid residues
L-isomers
Are the peptides found in peptidoglycan produced ribosomally or enzymatically?
Enzymatically
There are _______ layers of peptidoglycan in Gram-positive organisms and _______ layers of peptidoglycan in Gram-negatives
20-40; 1-2
What increases the structural integrity of bacterial cell walls?
Peptidoglycan subunits are cross-linked between the peptides
Describe the difference in the cross-linkage of peptidoglycan subunits in Gram-positive and Gram-negative cells
Gram negative: DAP to D-Ala via direct attachment
Gram positive: Glycine linker (D-Ala to L-Lys)
Describe how lysozymes damage bacterial cells, and where lysozymes are found
- An enzyme that damages the cell wall of bacteria by catalyzing hydrolysis of the 1,4-beta-linkages between NAG and NAM residues in peptidoglycan
- Defense of the innate immune response: lysozyme is present in various secretions including tears, saliva, and mucus.
Describe Transpeptidation/ Carboxypeptidase reactions
- Penicillin-binding proteins (PBPs) are the targets for penicillin and other β-lactam antibiotics
- Penicillin and related β-lactam antibiotics resembles the ‘transition state’ conformation of the D-Ala-D-Ala substrate when bound to these enzymes.
- Basically they make bacteria divert their resources so they can’t make peptidoglycan (as fast), so our body can catch up and kill the bacteria
Describe how the rigid cell wall of bacteria grows
- Peptidoglycan is constantly being synthesized and degraded.
- Autolysins (murein hydrolases) are used to aid in cell wall growth
- A group of enzymes that exist in all bacteria contains peptidoglycan and can break down the peptidoglycan chains in small sections to allow for growth and cell divisions
- Like lysozymes, they cleave the β-1,4 linkages in the glycan chain
- The process must be regulated as to not allow osmotic rupture of the cell
Describe teichoic and lipoteichoic acids
- Defined as polymers of chemically modified ribose or glycerol
- Only found in Gram-positive bacteria and are connected by phosphate groups (ester linkage)
- May be covalently modified with sugars, choline, or D-alanine groups that serve as antigenic determinants
Teichoic and lipoteichoic acids are only found in Gram-________ bacteria
positive
Teichoic acids may be covalently attached to the ________ _______, whereas lipoteichoic acid contains a lipid moiety that anchors the polymer in the _________ ________.
peptidoglycan layer; cytoplasmic membrane
LTA (lipoteichoic acids) are recognized by the innate immune system as what?
One of the conserved microbial structures (Pathogen Associated Molecular Pattern, aka PAMPs)
Describe the characteristics of gram-positive bacteria
- Thicker cell wall, no outer membrane, no LPS, no endotoxin, sensitive to lysozymes, more susceptible to penicillin
- Often have teichoic acid, some strains do sporulation, capsule is sometimes present, and some strains prudence exotoxins.
Describe the characteristics of gram-negative bacteria
- Thinner cell wall, has an outer membrane, has LPS, has endotoxins, no teichoic acid, no sporulation, resistant to lysozymes.
- More resistant to penicillin, sometimes has a capsule, and some strains produce endotoxins
Describe the discovery of Hans Christian Joachim Gram (1853-1938)
Discovery of Gram stains was made while attempting to distinguish between two pneumonia causing organisms: Streptococcus pneumoniae (Gram-positive) and Klebsiella pneumoniae (Gram-negative)
- Bacteria are primarily colorless (transparent) and exhibit a variety of shapes.
- Some bacteria have a thick “cell wall” (peptidoglycan), which stains _____ and is gram-positive.
- Some bacteria have only small amounts of peptidoglycan, which stains _____ and is gram-negative.
purple; red
Describe the 6 steps of a Gram stain
1) Spread bacteria out on a microscope slide using a drop of water or saline if needed, then bacteria are fixed onto the slide (and dead) using heat.
2) Then the slide is flooded with crystal violet, rinsed with water (by now all bacteria are purple).
3) Then the slide is flooded with iodine and rinsed with water.
4) Iodide exchanges with chloride ions in dye; iodide is bigger and causes dye to precipitate.
5) Then the slide is decolorize with alcohol for 2-5 seconds (this is a very easy step to mess up), then rinsed with water.
6) Alcohol permeabilizes the envelope of gram-negatives, so the precipitated purple dye comes out. The thick cell wall prevents dye from coming out in gram-positives.
Give 2 examples of bacterium that are exceptions to the Gram stain
1) Intracellular bacteria (i.e. bacteria that grow inside a eukaryotic cell)
2) Mycobacterium tuberculosis
Why doesn’t the Gram stain work on some bacteria?
The organisms produce a waxy coat [long-chain hydrocarbons, sugars, additional components], and waxy coats are resistant to acids
Describe an Acid-Fast stain
- Dye is introduced into tubercule bacteria using heat
- Washing in acid will not remove the dye [i.e., “acid-fast”]
What are the 3 ways to classify bacterial colony morphology?
Form, elevation, and margin
Describe the use of agar in the lab
- Agar has a semi-solid matrix and porous nature which allows for infusion of nutrients
- Bacteria-containing samples are either streaked or spread on plates to isolate individual bacterial cells
- Each colony grows from a single viable bacterium (a ‘colony-forming unit’ or CFU)
Define simple, comlex, enriched, selective, and differential mediums
1) Simple medium: defined, minimal nutrients
2) Complex medium: nutrients not precisely defined
3) Enriched medium: specific components added for “difficult to grow” bacteria
4) Selective medium: contains chemicals, antibiotics that inhibit some bacteria and allow growth of other bacteria
5) Differential medium: contains substates for biochemical reactions and indicators to illustrate the byproducts of reactions
What 3 characteristics of bacteria are important to know when studying colonies?
1) Some bacteria produce natural colors
2) Some bacteria secrete enzymes such as hemolysins (lyse RBCs)
3) Some bacteria ferment specific sugars
List 8 external bacterial structures
Flagella Pili Fimbriae Sex Pilus Type III Secretion Apparatus Capsule Glycocalyx (slime layer) Polysaccharides
Describe flagella and their importance
- Highly specialized, complex organelles for locomotion/ motility
- > 50 genes involved in assembly and function
- Very long proteinaceous filaments that have an a-helical arrangement [corkscrew-like]
- Apparatus spans the entire envelope of bacteria
- Within the host, flagella are critical for reaching mucosal surfaces (especially areas with fast flow)
Define monotrichous, lophotrichous, amphitrichous, and peritrichous flagellum
1) Monotrichous flagella: one flagella
2) Lophotrichous: multiple flagella (6-8) from one pole
3) Amphitrichous: one flagella on each of the two poles
4) Peritrichous: has flagella all over its body
List the 3 components of flagella
1) Basal body: anchored into the membrane
2) Hook region: extends just beyond the outer membrane
3) Helical filament: extends to the external environment
How are flagella assembled?
In a step-by-step manner using a specialized protein secretion pathway called type 3 secretion
How fast can flagella go?
Up to 100mph
Define microbiology
The branch of biology dealing with the structure, function, uses, and modes of existence of microscopic organisms.
True or false: Microbiology usually includes immunology, as well as the methods and technology used to study microbes
True
What 4 fields of study fall under the broad term ‘microbiology’?
Virology, mycology, parasitology, bacteriology
What did Jainism (600bc) and Mahavira believe about microbiology?
Mahavira asserted the existence of unseen microbiological creatures living in earth, water, air, and fire
The ancients called microbes “________ _______” and the Greeks called them “________ _______”
Ancients: ‘invisible spirits’
Greeks: anthropomorphic gods
What did the Roman Marcus Terentius Varro say about microbiology?
“there are certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and thereby cause serious diseases”
What was the prevailing theory of illness through the end of the 1800s?
The Miasma theory of bad air/ poisonous vapor
Girolamo Fracstoro (1546) asserted that disease is caused by invisible creatures placed in 3 categories; what were those 3 categories?
1) Those that infect by contact
2) Those that infect by fomites (any surface an “invisible creature” could be on)
3) Those that infect by distance
A lot of people denied the existence of microbes until we could see and study them, which happened during what century?
17th century (1600s)
What was the theory of spontaneous generation?
the theory that living organisms could develop from nonliving matter
What were the 3 pieces of evidence those who supported spontaneous generation used?
The ‘spontaneous generation of’:
1) Maggots on meat
2) Frogs on mud
3) Mice from grain
What was John Needham (1748)’s experiment in support of spontaneous generation, and why was the experiment flawed?
He applied heat to a broth and put a stopper on it; over time the broth became turbid. He asserted that it was sterile broth and that the creatures creating the turbidity spontaneously generated.
However, it was not sterile because the bottle of broth was open briefly after heating, and it may not have been boiled (unsure because Needham took terrible notes).
Who were the people who conducted the first two experiments that challenged spontaneous generation?
1) Francesco Redi (1665)
2) Lazzaro Spallanzani (1765)
What was Francesco Redi (1665)’s experiment?
He put one piece of meat in an unsealed flask, one in a flask sealed by a cork, and one flask covered by gauze. The unsealed flask had flies, maggots, ands eggs on it; the sealed flask had nothing on it; the flask covered with gauze had flies and fly eggs on the gauze because the flies could smell the meat.
What was Lazzaro Spallanzani (1765)’s experiment?
He heated broth and air in an open flask, and the flask became turbid. Then the did the same thing in a sealed flask, and the flask remained clear.
What was the experiment of Schwann and von Dusch (19th century)?
They found that if air was filtered through a cotton filter and attached to an otherwise sealed, previously heated flask, the flask would remain clear as long as the cotton filter was there.
What experiment did Louis Pasteur (late 19th century) conduct that helped disprove the theory of spontaneous genration?
He applied heat to two containers of unsterile broth, sterilizing them, and broke the neck of the first sterile flask, but kept the neck of the second sterile flask intact. He found that the microbes were trapped at the base of the second flask and it remained clear, but that the first flask became turbid.
What were Pasteur’s 4 major contributions to science?
1) Pasteurization: a technique invented by Louis Pasteur to sterilize liquid.
2) Vaccines: Pasteur helped create a couple vaccines.
3) Crystals: studied crystals and organic chemistry.
4) Microbial fermentation; certain microorganisms are able to take sugars and convert them into something different.
In 1836 and 1845 the fungal origin of what two diseases was discovered?
Silkworm disease and potato blight
Describe the effects of potato blight in the 1800s
-By 1800, the potato became the staple of life for Irish peasants
-In 1845, a “queer mist” came over the Irish Sea
Potato stalks turned black; potatoes began to putrify (smell bad)
-40% of the crop was destroyed
-Desperate for food, people ate anything they could scavenge (‘The Great Hunger’)
-Malnutrition leads to susceptibility to disease
-Began the process of migration (only ⅕ made it, so their ships were called ‘coffin ships’)
-Cause of the Great Hunger: having a single-crop economy
-Role of Potato Blight in World War I
Who is known as the “Father of modern infection control”?
Ignaz Simmelweis
Describe the discovery of Ignaz Simmelweis
In 1847 his midwives found that adequate hand hygiene can prevent transmission of puerperal fever
In 1867 _______ ________ created a method for the sterilization of operating instruments and antiseptic practice
Joseph Lister
What was Friedrich Henle’s major contribution towards microbiology?
In 1840, Friedrich Henle’s work began the “germ theory” of disease; wrote a famous essay called “On Miasma and Contagia”
Between 1860-4, _________ ________ demonstrated that fermentation and the growth of microorganisms in nutrient broths did not proceed by spontaneous generation
Louis Pasteur
In 1876, Robert Koch provided convincing evidence “germ theory” of disease with his work on what two things?
Bacillus anthracis and anthrax
What was the intent of Koch’s postulates?
To act as a set of criteria to establish the cause of an infectious disease
List Koch’s 4 postulates
1) Association of the microbe with the lesions of the disease
2) Isolation of the bacteria in pure culture
3) Showing that the isolated bacterium causes disease in humans or animals
4) Re-isolation of the bacterium from the intentionally infected animal
What were the problems with Koch’s postulates?
Multiple microbes can be responsible for different sickness symptoms at the same time, some microbes can’t be isolated in a pure culture, there might not be a suitable animal model, some infections don’t necessarily show lesions, and we can’t ethically infect humans with something deliberately.
What were the problems with Koch’s postulates?
Multiple microbes can be responsible for different sickness symptoms at the same time, some microbes can’t be isolated in a pure culture, there might not be a suitable animal model, some infections don’t necessarily show lesions, and we can’t ethically infect humans with something deliberately.
List the Molecular Koch’s Postulates proposed by Stanley Falkow (4 postulates)
1) Phenotype or property under investigation should be associated with pathogenic members of a genus or pathogenic strains of a species. The gene in question should be found in all pathogenic strains of the genus or species but be absent from nonpathogenic strains
2) Specific inactivation of the gene(s) associated with the suspected virulence trait should lead to a measurable loss in pathogenicity or virulence (animal model)
3) Reversion or allelic replacement of the mutated gene should lead
to restoration of pathogenicity.
4) The gene, which causes virulence, must be expressed during infection
What are the two main drawbacks to the Molecular Koch’s Postulates?
1) Not all pathogens have suitable animal models
2) Gene intractability: we have no idea how to manipulate the genes of some bacteria (ex: obligate intracellular bacteria).
If you have an infection and your doctor decides to use Koch’s postulates to help find the cause, what would be the 4 steps they would take?
1) Associate the lesion with disease
2) Swab the lesion to get the bacteria into a pure culture
3) Infect an animal with the bacteria culprit
4) Swab the animal’s lesion to reisolate the bacteria
If you have an infection and your doctor decides to use the Molecular Koch’s Postulates to help find the cause, what would be the 5 steps they would take?
1) Observe virulence in an infection causing strain of bacteria but not in other strains.
2) Measure the phenotype
3) Inactivate the virulent gene; virulence decreases
4) Reintroduce the virulent gene; virulence returns to normal
5) Virulent gene must be expressed during infection
What were the 4 main advances of the Golden Age of Microbiology?
Advances in cultivation techniques, immunology, identification of causative agents, and microbial ecology
What were the advances in cultivation techniques that came about during the Golden Age of Microbiology?
1) Gelatin to agar
- Gelatin melts at 25 degrees celsius and some bacteria degrade gelatin, whereas agar doesn’t melt until 100 degrees celsius
2) Richard Petri (dish)
What were the advances in immunology that came about during the Golden Age of Microbiology?
1) Bacterial attenuation
2) Vaccine success
What were the advances in microbial ecology that came about during the Golden Age of Microbiology?
1) Understanding contributions of soil bacteria (Winogradsky)
2) Public health measures were devised and implemented
- Health departments were created, diseases were monitored locally, and diseases were monitored internationally
The causative agents of what two illnesses were identified during the Golden Age of Microbiology?
Anthrax and tuberculosis
Microbes generate _____ of the oxygen we breathe
1/2
Only ___% of the cells that make up your body are mammalian
10%
Define basic microbiology
Studying microbes and defining their characteristics, typically in a lab.
Define applied microbiology
Exploiting microorganisms for a specific product or purpose (ex: wine and beer production, some food production, agricultural applications, cleaning oil spills applications, and renewable energy applications)
Define medical microbiology and name its subcategories
Defined as the study diseases of humans and animals
1) Clinical microbiology
2) Public health microbiology
3) Epidemiology
4) Immunology
Define microbial ecology and name its subcategories
Defined as how microbes interact with organisms and components of their habitats
1) Plant microbiology
2) Geomicrobiology
3) Biodegradation and bioremediation
4) Evolutionary/ archeological microbiology
Define agricultural microbiology and name its subcategories
Defined as the impact of microorganisms on agriculture
1) Soil microbiology
2) Food and dairy microbiology
Define industrial microbiology and name its subcategories
Defined as exploiting microbes for practical and technological use
1) R&D (Research and Development)
2) Biotechnology / Pharmaceutical
