Mircrobiology - Bacteria Flashcards
What is ribosome structure in Bacteria and Eukaryotes
- Bacteria - 70S ribosome (50S and 30S subunits)
2. Eukaryotes - 80S ribosome (60S and 40S subunits)
What the different bacteria shapes? (7)
- Coccus (Round)
- Bacillus (Long - Rod shaped)
- Cocobacillus (Round but long)
- Fusiform Bacillus (Oval Long)
- Vibrio (Curved)
- Spirillum (Spiral)
- Spirochete (Very Spiral)
Describe gram-positive bacterium (4)
Gram-positive:
- Purple stain.
- Only has a cell wall made of Beta lactamase with thick peptidoglycan layer.
- Penicillin-binding protein in Cytoplasmic membrane.
- Lipoteichoic acids in cell wall.
Describe gram-negative bacterium (4)
Gram-negative:
- Pink stain
- Outermembrane of Lioppolysaccharide, Porin channel and beta lactamse layer.
- Cell wall made of thin peptidoglycan.
- Penicillin-binding protein.
What is the structure of peptidoglycans? (3)
- 3 Dimensional Polymer
- Made up of N-acetylated sugars: glucosamine (NAG) and muramic acid (NAG) AND 5 amino acid peptides.
(amino acids make it resistant to enzyme destruction) - Cross-linked by Transpeptidase enzymes.
What are the peptidoglycan synthesis pathways unique to bacteria? These steps are important antibiotic targets (3)
- Polymerisation of sugars (for making backbone)
- Elongation of Amino acid side chains (to make peptides.
- Transpeptidase (for cross-linking)
What is the structure of Lipopolysaccharide (aka endotoxin)? (3)
- Long-chain fatty acid anchor (Lipid A) (active component)
- Core polysaccharide chain
- Variable CHO chain (=O antigen)
What are the functions of Lipopolysaccharide? (3)
- Major structural component of gram negative
- Effective permeability barrier (including to antimicrobials)
- Modulates host immune response.
What bacteria do not have a cell wall?
- M. pneumonia (pneumonia) and Urea plasma. These cannot be cultured or stained.
- Mycobacteria - have a very think lipid membrane made of mycolic acids which affect gram staining. This allows intracellular survival. ZN stain is used instead.
- Chlamydia trachomatis
What are the 3 ways Bacteria can grow? (2)
- Clusters e.g gram positive staphylococci
- Chains e.g gram positive streptococci
- Spores
How can bacterial growth be exploited to be identified? (3)
- Growth in chains or clusters, as well as size/shape when cultured.
- Enzymes, waste products excreted
- Growth requirements such as nutrients and atmosphere.
How can bacteria be classed based on atmospheric requirement?
- Aerobes - Uses O2
- Anaerobes - Use Fermentation, O2 usually toxic.
- Facultative Anaerobes - Can switch between Aerobes and Anaerobes metabolism.
What are some nutritional requirements of Bacteria? (3)
- Mostly Purines and Pyrimidines, amnio acids and vitamins.
- Escherichia Coli need just glucose and inorganic salts, so very easy to grow in lab.
- Treponema Pallidum (Syphillis) needs a specialised enriched medium so very hard to grow.
What are some Physical requirements for bacterial growth? (3)
- Temperature
- pH
- Salt Content
Describe the capsule of the bacteria (4)
- Polysaccharide coat to hide immunogenic cell wall.
- Immunity requires antibodies to capsule
- It has metabolic burden on bacterium
- It confers virulence e.g Haemophilus Influenzae
What are the different ways bacteria can move? (4)
- Chemotaxis - movement based on chemical stimuli
- Flagellum
- Pilus - using to grap and pull
- Corkscrew Motility e.g spirochete
How can bacteria stick to surfaces? (3)
- Docking (non-specific)
- Anchoring (specific) - where it binds to a specific receptor, maybe by fimbriae or Pili. This confers tissue tropism and host specificity.
- Biofilm formation - More resistant to immune response and antibiotics.
How can Bacteria Propagate? (3)
- Transduction - Introducing DNA to a recipient
- Conjugation - directly binds to recipient and transfers genetic info.
- Competence/transformation - dies and DNA is received by recipient.
What are the 2 mobile genetic elements in bacteria?
- Plasmids - Circular and extra-chromosomal DNA. They replicate independently and code for dozens of genes. Can be passed and transmitted by bacteria.
- Transposons - DNA sequences that move location in genomic DNA and plasmids. They encode for transposase and other genes.
Why are spores unique in bacterial growth?
- They are non-replicating and dormant.
- Resistant to drying, temp, disinfection and digestion.
This makes them important in clinical disease pattern and infection control.
How can gene regulation help Bacteria survive? (3)
- Conserving its energy
- Adapting to environmental changes
- Coordinated changes to multiple gene expression.
What are the different phases of Bacterial growth? (4)
- Lag phase: No increase in cell number when adjusting to new environment.
- Exponential phase: Cell doubling
- Stationary phase: Nutrients depleting, metabolites build up and division stops.
- Death Phase: Exhaustion of resources when in toxic environment.
