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102 Theme 4 > Lecture 2: Intro to Medical Microbiology > Flashcards

Lecture 2: Intro to Medical Microbiology Flashcards

1
Q

features of bacterial cells

A
  • 70S ribosome with 30S and 50S subunits
  • peptidoglycan cell wall
  • no nucleus or membrane bound organelles
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2
Q

features of eukaryotic cells

A
  • 80S ribosome with 60S and 40S subunits
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3
Q

what shape is a coccus bacteria

A

spherical

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4
Q

what shape is a bacillus bacteria

A

rod like

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5
Q

what shape is a coccobacillus bacteria

A

elongated spherical

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6
Q

how to do a Gram stain

A

1) smear colony on glass plate and heat fix
2) stain with crystal violet
3) wash off and add iodin. this will make a big insoluble complex with crystal violet and peptidoglycan
4) decolourise with alcohol/acetone
5) counterstain with safranin

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7
Q

what colour will a gram positive and negative bacterial cell go

A 
Positive = purple
Negative = piNk
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8
Q

explain how a Gram stain works on Gram positive bacteria

A
  • thick peptidoglycan cell wall

- peptidoglycan holds onto stain, not allowing it to be decolourised or restained with safranin

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9
Q

explain how a Gram stain works on Gram negative bacteria

A
  • thinner peptidoglycan cell wall
  • outer membrane dissolves away during decolourisation, so stain washes away
  • safranin can then counterstain it
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10
Q

which bacteria form chains down the microscope

A

streptococci

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11
Q

which bacteria form clusters down the microscope

A

staphylococci

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12
Q

requirements of aerobes

A

oxygen, as they use O2 as the terminal electron acceptor

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13
Q

requirements of anaerobes

A
  • also called obligate anaerobes
  • use organic molecule as terminal electron acceptor
  • eg glucose to lactic acid
  • O2 is usually toxic to these bacteria
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14
Q

features of facultative anaerobes

A

can switch between aerobic and anaerobic metabolism based on their current environment

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15
Q

what nutrients do bacteria require

A
  • purines and pyrimidines
  • amino acids
  • vitamins
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16
Q

requirements of E coli

A

only glucose and inorganic salts, making it very easy to culture

17
Q

requirements of Treponema pallidum (cause of syphilis)

A

specialised enriched medium making it fastidious and therefore hard to culture

18
Q

which bacteria don’t Gram stain and why

A
  • Mycoplasma and Chlamydia don’t have cell walls

- Mycobacterium just don’t stain with Gram stains

19
Q

features of peptidoglycan

A
  • Made up of N-acetylated sugars, eg glucosamine (NAG) and muramic acid (NAM)
  • also have 3-5 peptides which crosslink the NAG and NAM in a firm structure
  • cross-linked by transpeptidase enzymes produced by the bacteria (antibiotic target)
20
Q

how is peptidoglycan synthesised

A
  • polymerisation of sugars to make the backbone
  • elongation of amino acid side chains to add the peptides
  • transpeptidase to cross-link
21
Q

why don’t mycobacterium Gram stain

A
  • have a very thick lipid membrane (mycolic acid mycomembrane) anchored to the peptidoglycan layer
22
Q

features of a capsule

A
  • polysaccharide coat to hide antigens
  • metabolic burden on bacteria
  • gives the bacteria virulence
23
Q

mobile genetic elements of bacteria

A 
plasmid
- circular extra-chromosomal DNA
- independently replicating
- cross between bacteria (helps with antibacterial resistance)
transposes
- DNA sequences that are able to move location in the genome
- encode transposases and other genes
- move between genome and plasmid DNA
24
Q

features of spores

A
  • non-replicating dormant form of bacteria
  • resistant to drying, temperature, disinfection and digestion
  • come out of dormant phase when in less hostile environment
25
Q

draw graph of bacterial replication

A

check

26
Q

describe the phases of bacterial replication

A 
Lag Phase
- adapting to new environment
- no increase in cell numbers
Exponential Phase
- cell doubling occurs
Stationary Phase
- nutrients become depleted
- metabolites build up
- division stops
Death Phase
- exhaustion of all resources
- toxicity of environment

102 Theme 4 (11 decks)

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