Bacteriology Flashcards
What are the differences between eukaryotic and prokaryotic cells?
Eukaryotic:
- Nuclei with linear chromosomes
- Organelles: mitochondria, Golgi apparatus, lysosomes and relatively large ribosomes
- Larger size: 0.1 – 100 μm
- Individual cells replicate by mitosis
Prokaryotic :
- Lack true membrane - bound nuclei
- Genetic information is contained in a single haploid circular chromosome
- Small size: 0.5-5 μm
- Bacteria: Unicellular organisms that replicate by binary fission - Bacteria: extrachromosomal DNA - plasmids
What are the similarities between eukaryotic and prokaryotic cells? (3)
- Cell membrane
- Cytoplasm
- DNA present in both (just different location)
- Ribosomes (but different structure)
What are the different structures of the bacterial ? (the ones they all have) (5)
- Cytoplasm
- Ribosomes
- Nucleoid
- Plasma membrane
- Complex and rigid cell wall
What are the structures the bacterial can sometimes have? (3-4)
- Capsule
- Flagella
- Pili/Fimbriae
(Endospores)
(OLD) What does the cytoplasm contains?
- MACROMOLECULES (proteins, mRNA, tRNA) + Nucleoid (DNA) and ribosomes (protein synthesis).
- SMALL MOLECULES : energy sources, precursors of macromolecules, metabolites or vitamins.
- INORGANIC IONS : for enzymatic activity.
(OLD) What is the functions of the cytoplasm?
- Facilitate chemical reactions
- Dissolve solutes (ex. carbohydrates and proteins)
What is the nucleoid in the prokaryotic cells?
It is the location in the prokaryotic cell where primary genetic material is found. Takes 1/3 of the cell.
What is the chromosomal DNA made of?
Single haploid circular chromosome containing double-stranded DNA. (Haploid meaning : no additional copies).
What are the ribosomes? Function?
- PROTEINS and RNA
Function: involved in protein synthesis!
What is the plasmid?
It is a circular molecule of DNA that replicates separately from the genome.
(several different types may be present in one cell)
Is the plasmid part of the nucleoid?
NO!
Is the plasmid genes essential under normal conditions?
No, it is not essential.
(Old) What is the functions of the plasmid? (2)
- SPECIAL GENES REPLICATION:
- Virulence factors: associated with disease
- Resistance genes: to survive in presence of antibiotics and other toxic compounds.
- CONJUGATIVE PLASMIDS: cell-to-cell transfer by conjugation (transfer DNA).
(Old) How can we relate ribosomes to medicine? How can they be used?
They can be the target for antibiotics.
(Old) What are the different components of the bacterial envelope?
- Cytoplasmic or plasma membrane.
- Cell wall (peptidoglycan layer)
- Periplasmic space
- Capsule (some bacteria)
(Old) Where the plasma membrane located?
Innermost membrane, next to cytoplasm.
(Old) What type of bacteria has a periplasmic space?
Gram negative
(Old) What are composed the components of the plasma membrane?
Phospholipid bilayer (head hydrophilic and tail hydrophobic).
(Old) What can pass by passive diffusion the plasma membrane?
Only hydrophobic coumpounds.
(Old) What the different proteins inside the plasma membrane?
- TRANSPORT PROTEINS : for specific transport of molecules into and out of the cell.
- ENERGY GENERATION COMPONENTS : used to generate ATP.
- Proteins to work as anchors or assembly of external structures.
What is the main functions of plasma membrane?
- Selective permeable membrane
What are the components of the cell wall? How are they arranged?
Peptidoglycan (unique to prokaryotic cells) : NAG + NAM.
Arranged in a mesh-like structure alternating NAG-NAM-NAG-NAM.
(Old) What is the link between each NAG and NAM?
Cross-linked with peptides by transpeptidase enzymes called: penicillin-binding proteins (PBPs).
What is the function of the cell wall?
- RIGIDITY
- PROTECTION against mechanical damage and osmotic lysis
What does contains the cell wall of gram +, gram - and mycobateria ?
Gram + : (Lipo)teichoic acid: strongly antigenic
–> High resistance to physical disruption and drying
Gram - : Lipopolysaccharides (LPS)
–> Low resistance to physical disruption and drying
Mycobacteria: mycolic acid as virulence factor
–> will not stain = need acid fast stain!
Is there an outer membrane in every bacteria?
No, usually common to Gram-negative bacteria.
What are the 2 part of LPS in Gram - ? What is the most important of the 2? What is its function?
- Lipid A : endotoxin that activates immune system and exert harmful effects
- Polysaccharide chain: antigenicity
What is the function of outer membrane?
- Selective permeability
- Resistance to large or hydrophobic toxic compounds
- Tolerance to detergents and bile salts
Is the gram + or gram - that has the thickest cell wall (peptidoglycan layer)?
Gram +
Is the capsule present in all bacteria?
No!
What is the capsule?
Polysaccharide outer layer!
What is the functions of the capsule?
- PROTECTION from adverse environmental conditions
- Facilitate ADHERENCE to surfaces
- Help EVADE phagocytosis
- NUTRIENT RESERVE
In what type of cell state are found endospores?
- Cryptobiotic state of DORMANCY –> most durable type of cell found in nature
What is the main function of endospores?
Ensure survival during adverse environmental conditions
dormant highly resistant bodies
What are the only 2 genera that can transform into endospores when exposed to adverse conditions?
Clostridium and Bacillus
Where is the flagella? Which bacteria specie is most commonly presenting with flagella?
On the surface of the bacteria.
–> Present in many species of Gram -
Is there always only one flagella and at the same place?
No! It can have number of flagella and at different position.
What is the function of the flagella?
Locomotion or bacterial motility
What does the pili/fimbriae look like?
Fine, straight, hair-like appendages attached to cell wall.
What’s an endoflagella? What movement does it do?
Flagella in the periplasmic space = corkscrew-like motility (e.g. spirochete)
What are the 2 functions of pili/fimbriae?
- Adhesion to host tissues
- Contribute to antigenicity
(Old) What structures contribute to bacterial survival ?
- Plasmid (resistance genes: can survive in presence of antibiotics and other toxic compounds)
- Endospores (ensure survival adverse environmental conditions)
- Capsule (protects from adverse environmental conditions)
- Outer membrane : resistance to large or hydrophobic toxic compounds
- Cell wall : protects against mechanical damage and osmotic lysis.
(Old) What structures contribute to pathogenesis?
- Plasmid : genes associated with disease (virulence factors)
- Capsule : virulence factor that facilitate adherence to surfaces and interfere with phagocytosis.
- Pili/Fimbriae : contribute to antigenicity
What are the different types of bacterial shapes?
- Cocci
- Bacilli
- Budding and appendaged bacteria
- Others +++ (look at ppt)
(+/- old) What are the different types of bacterial arrangements?
- Alone (e.g. coccus)
- Two (e.g. diplobacilli)
- Chain (e.g. streptococci or streptobacilli)
- Encapsulated (e.g. diplococci)
- Organized bundle (e.g. staphylococci or pallisades in bacilli)
What are the 3 exceptions to general bacterial properties?
- Mycoplasma: does not have a cell wall
- Leptospira: two circular chromosomes
- Borrelia burgdorferi: linear chromosomes
(Old) If you grow two bacteria from the same species, will they absolutely be the same morphology? Why?
No, it depends on the culture medium, incubation time, temperature, oxygen or genetic differences.
What are the different type of sources of metabolic energy?
- Fermentation
- Respiration
- Photosynthesis
What are the different nutrients required for different bacterial groups?
Carbon and Nitrogen (about 99,9% of bacteria need those nutrient)
What are the different types of oxygen requirement fro growth? (4)
- Obligate aerobes (die without O2)
- Obligate anaerobes (die with O2)
- Facultative anaerobes (can switch to O2 metabolism to CO2 metabolism)
- Microaerophile: need a little O2
(Old) Aerotolerant anaerobes (use fermentation, so don’t use O2, but can survive and grow with O2)
What are the different classifications of bacteria based on temperature range of growth (from cold to warm)?
Most of them are…
- Psychrophiles (10°C)
- Psychrotropes (20°C)
- Mesophiles (35°C)
- Thermophiles (60°C)
- HYperthermophiles (90°C)
Most of them are… Mesophiles (like about 37°C)
(Old, but good summary) What is the different cell envelope type for the different classes of cell (gram +, gram -, mycobacteria, mollicutes)? From cytoplasm to outside (ECF) for each.
GRAM POSITIVE : - plasma membrane - periplasmic space (with lipoprotein) - peptidoglycan - ECF GRAM NEGATIVE : - plasma membrane - periplasmic space (with lipoprotein) - peptidoglycan - another periplasmic space - outer membrane - ECF MYCOBACTERIA : - plasma membrane - periplasmic space (with lipoprotein) - peptidoglycan - Mucolic acid on the cell - ECF MOLICUTES : - plasma membrane, BUT with sterols - periplasmic space (with lipoprotein) (No peptidoglycan layer)
What color do the gram + and gram - stain?
Gram - : pink
Gram + : purple
True or false : does bacterial growth curve replicate like virus, by assembly line.
False, they replicate by binary fission.
(Old) How long can it take to create 2 daughter cells (generation time)?
30 minutes to 20 hours.
During which phase in bacterial growth curve occurs cell multiplication is at maximal rate?
Exponential phase or Logarithmic phase (2nd)
During which phase in bacterial growth curve is there no cell division, only increase in size?
Lag phase (1st) (active metabolism of cells, but no division yet)
In which phase exhaustion of nutrients or accumulation of toxic products occur? And what happens because of it?
Maximal stationary phase (3rd).
The growth will cease.
There’s a balance between slow multiplication and death rate.
When does the cell division starts to occur?
Exponential phase or Logarithmic phase (2nd)
What happens after exhaustion of nutrients phase?
Decline phase or death phase: progressive death of cells (4th, Last phase)
What are the main differences between exotoxins and endotoxins?
Exotoxins: proteinaceous toxins made inside the bacteria and released in extracellular enviro.
- -> exert action on specific cells
- -> Heat labile
Endotoxins: toxins in the cell wall of the bacteria (e.g. LPS)
- -> induce inflammation by stimulating the immune system
- -> Heat stable
What is the biofilm made of?
Bacteria aggregation (all holding hands!) –> on a surface and enclosed into in a bipolymer matrix surface
What is the main function of the biofilm? And where do you usually find it?
Because they are all enclosed in the same bipolymer matrix surface they can exchange nutrients
+ they can produce LPS
Usually found in… dental plaques, catheter, urinary tract infection
What is quorum sensing? How does it work?
- -> Bacteria produce small signal molecules (pheromones, autoinducers) by which they communicate
- -> When the population reaches a defined density (a bacterial quorum), instant changes occur in their behaviour (virulence), appearance and metabolism.
What the different group behaviors from quorum sensing?
Symbiosis Virulence Conjugation Biofilm Motility ATB production Sporulation Competence
How can bacteria transfer virulence between bacteria?
By conjugation, transformation or transduction!
• Plasmids (small circular DNA) and bacteriophages (viruses of bacteria) may carry genes for antibiotic resistance, toxins
Most common: conjugation!
(capsules and fimbriae can mediate transfer)
See PPT for Fungi, but here are the main points!
- Eukaryotic, non-photosynthetic microorganisms widely distributed in the environment
- Heterotrophs: produce exoenzymes to obtain nutrients by absorption
- Cell wall contains chitin (plant-like cell wall).
- Two major forms: branching hyphae (moulds) and unicellular yeasts
- Reproduce both sexually (spores) and asexually (spores, budding or fragmentation)
- Resistant to antimicrobial drugs**
- Vast majority of fungi are saprophytes and non-pathogenic.
- Fungal infections are far less common than bacterial infections.
- Fungi grow aerobically and many are strict aerobes (NEED O2)
- Mechanisms involved in fungal diseases
• Tissue invasion (mycosis): E.g. dermatomycoses, dermatophytoses
• Toxin production (mycotoxicosis): E.g. ingestion of fungal toxins pre-formed in stored food or standing crops
• Induction of hypersensitivity (less common): E.g. chronic pulmonary disease in cattle and horses
True or False. An infection does not always result in disease! But all infectious diseases are
communicable and not all communicable (reportable) diseases are infectious.
False!
(true part: An infection does not always result in disease!)
–> All communicable (reportable) diseases are infectious, but not all infectious diseases are
communicable
Bacteria are usually intracellular or extracellular?
Extracellular!
What is the purpose of being a pathogen or at times adopting a pathogenic lifestyle?
Enhance transmission!
WHERE or WHEN would you like to collect fungi and bacteria?
Fungi: specimens should be collected from the periphery of active lesions
Bacteria: collect before starting any antimicrobial therapies
