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Microbiology > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

What are the 4 types of envelope modifications in prokaryotes?

A

1) Capsules and slime layers
2) S-layer
3) Flagella
4) Pili

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2
Q

What is a tightly attached “slime” called?

A

capsule

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3
Q

What is a loosely attached “slime” called?

A

slime layer

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4
Q

What is “slime” made of?

A

high-molecular-weight polysaccharide

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5
Q

Is the slime layer/capsule a target for vaccines? why?

A

yes, bc it’s the first bacterial structure encountered by immune system

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6
Q

What is capsular polysaccharides (CPS) usually composed of? charge?

A

typically negatively charged and can form 200 sugars long

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7
Q

Serotyping uses what to help distinguish isolates?

A

CPS

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8
Q

What allows insertion of the CPS into the membrane?
name? attached by what?

A

a phospholipid attached to the end of the CPS (hydrophobic)
called lyso-phosphatidylglycerol attached by Kdo linker

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9
Q

What are the 4 functions of the capsule?

A

1) acts as a sponge to retain water and nutrients
2) protection against desiccation
3) limits diffusion of harmful chemicals
4) aids in surface adherence and biofilm formation

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10
Q

How does the capsule protect against immune evasion?

A

protects against complement system
and via cationic antimicrobial peptide resistance (positively charged and bacteria is negatively charged)

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11
Q

How can you assay for capsule in the lab? (4)

A

1) Electron microscopy
2) calcofluor
3) biochemical isolation
4) capsule stain

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12
Q

Procedure of capsule stain?

A

1) coat with india ink
2) air dry (heat melts sugar in capsule)
3) saturate with crystal violet for 1 min
4) rinse with water and air dry, look under microscope

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13
Q

What is the role of the s-layer?

A

protection, structural support, permability barrier, mediate binding

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14
Q

Where is the s-layer found?

A

bacteria and archea

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15
Q

Where is the s-layer? for bacteria

A

anchored to the cell wall of Gram-positive bacteria and to the outer membrane of Gram-negative bacteria

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16
Q

Where is the s-layer? for archea

A

either cell wall or directly to the cell membrane

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17
Q

What is the s-layer made of? unique ability?

A

glycoproteins
can self assemble

18
Q

What is the role of flagella?

A

locomotion

19
Q

what is flagella at the end of a cell called?

A

polar

20
Q

what is flagella all over the cell called?

A

perotrichous

21
Q

more than one flagella?

A

flagellum

22
Q

What is the structure of a flagellum?

A

1) long helical filament
2) connecting hook
3) basal body equipped with a rotor to turn the flagellum

23
Q

Wha is the rotor power by?

A

proton motive force

24
Q

What is the flagellum filament made of? structure?

A

rigid helical hollow structure made of flagellin that self-assembles

25
Q

What is it important that the flagella is highly antigenic?

A

immune system can recognize

26
Q

What is the structure of the hook?

A

short joint, curved

27
Q

What is the basal body made of?

A

around 15 proteins that form a rod and anchors structure to cell membrane

28
Q

What does CCW rotation move the bacteria?

A

foward

29
Q

What does CW rotation move the bacteria?

A

tumble in place

30
Q

how is a random walk produced?

A

alternating CCW and CW

31
Q

What are endoflagella? ex?

A

flagella contained within periplasm, ex spriochetes

32
Q

Why do few gram-positive bacteria have pili?

A

pili attach to the outer membrane which Gram+ bacteria do not have

33
Q

Do pretty much all Gram- have pili or fimbriae?

A

yes

34
Q

What are pili or fimbriae?

A

thinner and shorter flagella distributed in large numbers over the surface

35
Q

Function of pili or fimbriae? (3)

A

1) attachement to surfaces
2) conjugation (transfer DNA/RNA)
3) motility

36
Q

What is pili composed of?

A

oligomeric pilin proteins

37
Q

what is the bottom/base of the pili called?

A

pilus

38
Q

what is twitching motility?

A

pili are sticky and this is how they move,
extends and retraction due to polymerization and depolymerization

39
Q

How do we assay motility in the lab?

A

1) dip sterile toothpick into bacterial suspension
2) poke swim agar with toothpick
3) incubate at desired temperature and measure zone of motility

40
Q

what is the zone of motility?

A

diameter of colony

41
Q

How do we know which part of the flagellum are crucial for motility?

A

mutants lose parts of flagellar apparatus and look for small zones of motility in assay motility

Microbiology (17 decks)

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