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Flashcards in Mircrobiology - Bacteria Deck (22)
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1
Q

What is ribosome structure in Bacteria and Eukaryotes

A
  1. Bacteria - 70S ribosome (50S and 30S subunits)

2. Eukaryotes - 80S ribosome (60S and 40S subunits)

2
Q

What the different bacteria shapes? (7)

A
  1. Coccus (Round)
  2. Bacillus (Long - Rod shaped)
  3. Cocobacillus (Round but long)
  4. Fusiform Bacillus (Oval Long)
  5. Vibrio (Curved)
  6. Spirillum (Spiral)
  7. Spirochete (Very Spiral)
3
Q

Describe gram-positive bacterium (4)

A

Gram-positive:

  1. Purple stain.
  2. Only has a cell wall made of Beta lactamase with thick peptidoglycan layer.
  3. Penicillin-binding protein in Cytoplasmic membrane.
  4. Lipoteichoic acids in cell wall.
4
Q

Describe gram-negative bacterium (4)

A

Gram-negative:

  1. Pink stain
  2. Outermembrane of Lioppolysaccharide, Porin channel and beta lactamse layer.
  3. Cell wall made of thin peptidoglycan.
  4. Penicillin-binding protein.
5
Q

What is the structure of peptidoglycans? (3)

A
  1. 3 Dimensional Polymer
  2. 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)
  3. Cross-linked by Transpeptidase enzymes.
6
Q

What are the peptidoglycan synthesis pathways unique to bacteria? These steps are important antibiotic targets (3)

A
  1. Polymerisation of sugars (for making backbone)
  2. Elongation of Amino acid side chains (to make peptides.
  3. Transpeptidase (for cross-linking)
7
Q

What is the structure of Lipopolysaccharide (aka endotoxin)? (3)

A
  1. Long-chain fatty acid anchor (Lipid A) (active component)
  2. Core polysaccharide chain
  3. Variable CHO chain (=O antigen)
8
Q

What are the functions of Lipopolysaccharide? (3)

A
  1. Major structural component of gram negative
  2. Effective permeability barrier (including to antimicrobials)
  3. Modulates host immune response.
9
Q

What bacteria do not have a cell wall?

A
  1. M. pneumonia (pneumonia) and Urea plasma. These cannot be cultured or stained.
  2. Mycobacteria - have a very think lipid membrane made of mycolic acids which affect gram staining. This allows intracellular survival. ZN stain is used instead.
  3. Chlamydia trachomatis
10
Q

What are the 3 ways Bacteria can grow? (2)

A
  1. Clusters e.g gram positive staphylococci
  2. Chains e.g gram positive streptococci
  3. Spores
11
Q

How can bacterial growth be exploited to be identified? (3)

A
  1. Growth in chains or clusters, as well as size/shape when cultured.
  2. Enzymes, waste products excreted
  3. Growth requirements such as nutrients and atmosphere.
12
Q

How can bacteria be classed based on atmospheric requirement?

A
  1. Aerobes - Uses O2
  2. Anaerobes - Use Fermentation, O2 usually toxic.
  3. Facultative Anaerobes - Can switch between Aerobes and Anaerobes metabolism.
13
Q

What are some nutritional requirements of Bacteria? (3)

A
  1. Mostly Purines and Pyrimidines, amnio acids and vitamins.
  2. Escherichia Coli need just glucose and inorganic salts, so very easy to grow in lab.
  3. Treponema Pallidum (Syphillis) needs a specialised enriched medium so very hard to grow.
14
Q

What are some Physical requirements for bacterial growth? (3)

A
  1. Temperature
  2. pH
  3. Salt Content
15
Q

Describe the capsule of the bacteria (4)

A
  1. Polysaccharide coat to hide immunogenic cell wall.
  2. Immunity requires antibodies to capsule
  3. It has metabolic burden on bacterium
  4. It confers virulence e.g Haemophilus Influenzae
16
Q

What are the different ways bacteria can move? (4)

A
  1. Chemotaxis - movement based on chemical stimuli
  2. Flagellum
  3. Pilus - using to grap and pull
  4. Corkscrew Motility e.g spirochete
17
Q

How can bacteria stick to surfaces? (3)

A
  1. Docking (non-specific)
  2. Anchoring (specific) - where it binds to a specific receptor, maybe by fimbriae or Pili. This confers tissue tropism and host specificity.
  3. Biofilm formation - More resistant to immune response and antibiotics.
18
Q

How can Bacteria Propagate? (3)

A
  1. Transduction - Introducing DNA to a recipient
  2. Conjugation - directly binds to recipient and transfers genetic info.
  3. Competence/transformation - dies and DNA is received by recipient.
19
Q

What are the 2 mobile genetic elements in bacteria?

A
  1. Plasmids - Circular and extra-chromosomal DNA. They replicate independently and code for dozens of genes. Can be passed and transmitted by bacteria.
  2. Transposons - DNA sequences that move location in genomic DNA and plasmids. They encode for transposase and other genes.
20
Q

Why are spores unique in bacterial growth?

A
  1. They are non-replicating and dormant.
  2. Resistant to drying, temp, disinfection and digestion.

This makes them important in clinical disease pattern and infection control.

21
Q

How can gene regulation help Bacteria survive? (3)

A
  1. Conserving its energy
  2. Adapting to environmental changes
  3. Coordinated changes to multiple gene expression.
22
Q

What are the different phases of Bacterial growth? (4)

A
  1. Lag phase: No increase in cell number when adjusting to new environment.
  2. Exponential phase: Cell doubling
  3. Stationary phase: Nutrients depleting, metabolites build up and division stops.
  4. Death Phase: Exhaustion of resources when in toxic environment.