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Dynamic Cell > Intro to bacteria > Flashcards

Intro to bacteria Flashcards

1
Q

Helicobacter pylori

A

stomach ulcers

helical shape
- penetrate stomach mucus

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2
Q

Proteus mirabilis

A

UTIs

long cell length
- cells align + use group swarming motility
cells can’t move in small group

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3
Q

Features prokaryotes vs eukaryotes

  • cell wall
  • nucelar membrane
  • nucleolus
  • no. of chromosomes
  • mitochondria
  • ribosomes
A 
P = contains peptidoglycan 
E = no peptidoglycan 
P = absent
E = present 
P = absent
E = present 
P = 1
E = >1
P = absent
E = present
P = 70S
E = 80S
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4
Q

cell envelope

A

provides interface between bacteria + enviro

maintains cell integrity

protein or sugar capsule

external structures for adhesion or motility
(pili, flagella)

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5
Q

bacteria in distilled water

A

can maintain shape + integrity

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6
Q

gram +ve

  • features
  • examples
A

thick cell wall

multiple peptidoglycan layers

interspersed w/ teichoic acids (anchor peptidoglycan to membrane)

Staphylococcus
Streptococcus

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7
Q

gram -ve

  • features
  • examples
A

think peptidoglycan wall

enclosed by OM of LPS

no teichoic acids

periplasmic space contains peptidoglycan

Escherichia
Pseudomonas

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8
Q

Gram staining

A
  1. heat fix bacterial smear to glass
  2. stain w/ crystal violet
    = violet cells
  3. fix w/ Gram’s iodine
    = violet cells
  4. de-colourise w/ alcohol
    = violet or colourless
  5. stain w/ safarin
    = red
  6. wash with water
    = +ve = purple
    -ve = red
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9
Q

peptidoglycan

- structure

A

made of linear glycan chains

cross-linked by short peptide chains

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10
Q

glycan

- structure

A

alternating units of:
N-acetylglucosamine
N-acetylmuramic acid

joined by beta 1,4-glycosidic links

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11
Q

antimicrobial agents acting on peptidoglycan

  • how?
  • examples
A

some work intracellularly
- prevent precursor synthesis

some prevent cross-linking

penicillin
vancomycin

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12
Q

adding beta-lactam AB to a cell

e.g. in S. aureus

A

prevents pentaglycine cross link

weakens cell wall
-> cytoplasmic membrane forces its way out

cell wall breaks down
-> cytoplasmic membrane now outermost structure
= spheroplast

= osmotically fragile

  • easily take up water
  • > bursts
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13
Q

Lysozyme in S. aureus

A

breaks glycosidic bonds between sugars

-> breaks down peptidoglycan cell wall

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14
Q

cytoplasmic membrane

A

highly selective barrier

phospholipids + proteins

larger molecules must be transported

no cholesterol

v fluid

site for energy generation

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15
Q

cytoplasmic membrane

- site for energy generation

A

charged ions e.g. H+ cannot move freely across membrane
-> gradients form

efflux of H+

  • > electrochemical gradient (proton motive force)
  • > powers processes
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16
Q

LPS

endotoxin

A

feature of gram -ves

can continue to cause damage even after cells die

-> due to toxic effect of LPS OM
(AKA endotoxin)

(LPS isn’t removed by sterilisation)

17
Q

LPS

structure

A

O antigen
= repeating chains of polysaccharides
<200 residues

Core
= ~5 sugar residues w/ side chains

Lipid A
= dimer of phosphoglucosamine residues w/ 2 fatty acid chains linked to each sugar residue

18
Q

LPS

- general effects

A

fever

intravascular coagulation 
(activates blood clotting factors)

vasodilation
-> hypotension (low BP)

shock
-> due to hypotension

CAN BE FATAL

19
Q

N. meningitis

A

gram -ve

septicaemia phase as part of pathogenesis

sheds LPS into blood during septicaemia
-> complications

treatment w/ ABs

  • > enormous LPS release
  • > fatal?
20
Q

capsules

-features

A

many gram-ve and some gram +ve
produce extracellular polysaccharide (EPS)

discrete capsule or generalise slime layer

21
Q

capsules (EPS)

- functions

A

adherence

resistance
- to AMs, desiccation, macrophages

immune evasion + virulence

22
Q

capsules

- example

A

S. pneumoniae
- needs capsule for pathogenicity

-> shields cell from IS detection

23
Q

bacterial chromosome

A

nucleoid
= chromosomal DNA localised to are of cytoplasm + anchored to cytoplasmic membrane

series of highly folded loops
- but NOT bound a membrane

24
Q

plasmids

A

autonomously replication extrachromosomal DNA

circular dsDNA

HGT between species

accessory functions conferring advantage
- AB resistance, produce toxins

Dynamic Cell (15 decks)

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