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Cells to Organisms - Lectures > Lecture 7. Bacterial Cell Envelope Part 2. > Flashcards

Lecture 7. Bacterial Cell Envelope Part 2. Flashcards

1
Q

What is beyond the outer membrane and cell wall ?

A
  1. Capsules, EPS and biofilms
  2. S-layers
  3. Fimbriae and pili
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2
Q

What does EPS stand for ?

A

Extra cellular polysaccharides

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3
Q

What do capsules, EPS and biofilms have in common ?

A
  1. Outermost layer of protection
  2. Common structure, biogenesis and export pathways
  3. Assists in adhesion and solid surfaces
  4. Protects against antibiotics, antimicrobial peptides and host immune responses
    5
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4
Q

Where are capsule polysaccharides retained ?

A

On cell surfaces

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5
Q

What happens to EPS ?

A

They are secreted

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6
Q

What happens to biofilms ?

A

Product of multiple extra cellular bacteria producing EPS

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7
Q

What is a capsule ?

A

A type of glycocalyx

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8
Q

What is meant by distinct, gelatinous ?

A

Capsule

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9
Q

What is meant by slime layer ?

A

Irregular, diffuse

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10
Q

What does a capsule have in terms of water ?

A

High water content

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11
Q

What is the capsule important for ?

A

Virulence – resists phagocytosis

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12
Q

What is the function of capsule ?

A
  1. Barrier to toxic hydrophobic molecules
  2. Protection against dessication
  3. Resistance to bacteriophage
  4. Evade host defences
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13
Q

What does a capsule that avoids detection do ?

A

Hide surface structures – resist phagocytosis

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14
Q

What does a capsule do to avoid destruction ?

A

Prevent complement-mediated lysis

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15
Q

Where are opsonins directed to ?

A

Cell envelope components are deposited beneath the capsule layer

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16
Q

What is an opsonin ?

A

Substances that bind to foreign micro-organisms making them more susceptible to phagocytosis

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17
Q

What does capsule do to opsonin ?

A

Inhibits access

18
Q

What often are invasive bacterial pathogens ?

A

Encapsulated

19
Q

What are EPS important for ?

A

The structure and function of biofilms

20
Q

What are bacteria in biofilm ….

A
  1. Impervious to phagocytosis by neutrophils and macrophages
  2. Resistant to antimicrobial peptides and complement
  3. Semi-dormant - difficult to inhibit with antibiotics
21
Q

What are biofilm associated infections ?

A
  1. S. aureus

2. S. epidermis

22
Q

What does Pseudomonas aeruginosa biofilms do ?

A

Cause cystic fibrosis in lung infections

23
Q

What is a s-layer ?

A

Extracellular layer coating the entire bacterial cell surface

24
Q

Where are s-layers found ?

A
  1. Gram positive bacteria
  2. Gram negative bacteria
  3. Archaea
25
Q

What are s-layers composed of ?

A

Protein or glycoprotein

26
Q

What is the structure of s-layer ?

A
  1. Protein subunits come together to form selection of arrays
  2. Porous mesh
  3. Protective barrier
  4. Selective permeability
27
Q

What are the functions of s-layer ?

A
  1. Molecular sieve
  2. Protection
  3. Adherence to host cell surfaces
28
Q

What are pili made of ?

A

Pilin protein

29
Q

What are the two types of pili ?

A
  1. Sex pili

2. Ordinary pili

30
Q

What do pili do ?

A
  1. Attach to other bacteria

2. Motility

31
Q

Where are pili mostly found ?

A

Gram negative bacteria

32
Q

What type of pili are found in P. aeruginosa ?

A

Type 4 pili

33
Q

What do type 4 pili do ?

A
  1. Adherence to surfaces
  2. Biofilm formation
  3. Twitching motility
  4. Senses initial contact with surfaces
34
Q

What are fimbriae ?

A

Bristle like fibers present in large numbers

35
Q

What do fimbriae do ?

A

Help attach cells to a solid surface or tissues

36
Q

What do fimbriae do to bacteria?

A

Help bacteria cling together

37
Q

Where are fimbriae found ?

A

Gram negative and gram positive

38
Q

Where do fimbriae recognise host molecules ?

A

Adhesin present at tip

39
Q

What is the structure of fimbriae in E.coli ?

A
  1. FimH tip protein - adhesin
  2. 3nm thick tip fibrillum composed of 2 proteins
  3. 7nm thick helical rod–subunits of fimA
40
Q

What are virulence factors during bladder infection ?

A

Type 1 fimbriae fimH and P fimbriae

41
Q

Where do fimbria adhere to in bladder infection ?

A

Uroepithelial cells of baldder

42
Q

What is the receptor in bladder infection ?

A

Mannose containing glycoproteins

Cells to Organisms - Lectures (36 decks)

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