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Physiology of Microbes > Motility Regulation L11 > Flashcards

Motility Regulation L11 Flashcards

1
Q

what is bacterial motility

A

control of gene expression and adaptation to the environment

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2
Q

what must be achieved for flagellum components to be produced in correct order

A

temporal gene expression

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3
Q

what is the internal structure of flagellum like

A

genes required for assembly of each part of the flagellum need to be produced in a specific order

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4
Q

what is RNA polymerase holoenzyme like

A

consists of six protein subunits
Core enzyme (five subunits)
Sigma factor

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5
Q

what does the sigma factor bind to in transcription

A

-10 and -35 sequences in bacterial promoters and identifies the beginning of a gene

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6
Q

what does sigma 28 control production of

A

Structural genes for flagellin production

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7
Q

what prevents the structural flagellin genes being expressed

A

not expressed until basal body is complete

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8
Q

where is sigma 28 in cell

A

σ 28 is made continuously by the cell but is bound to an ANTI-sigma factor protein (FlgM)

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9
Q

what happens when basal body is complete

A

FlgM is exported from cell

σ 28 released and induces expression of the structural genes

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10
Q

what causes temporal gene expression

A

Mechanism ensures that flagellin is made after the basal body is formed
Results in correct temporal gene expression

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11
Q

what are the steps that occur during temporal gene control of flagellum assembly

A

σ28 and FlgM (anti-sigma factors) made
FlgM stops σ28 binding to promoters = no flagellin synthesis
Basal body is made using σ70 = no flagellin synthesis as inside cell FlgM conc high
FlgM exported through basal body
Flagellin gene induced by free σ28
flagellin exported, flagellum assembled

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12
Q

what is flagellin

A

surface antigen

H antigen

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13
Q

what is the benefit of variable flagellum

A

when bacteria encounter host will want to invade immune system
variable flagellum good as if already seen flagellum will destroy but if different will not as not seen before

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14
Q

what os E.coli O:157 H:7

A

Flagellin is H antigen flagellin variant is 7

O:157 is numbered variant of LPS

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15
Q

what do many pathogens do to prevent detection

A

many pathogens switch OFF flagellin genes in response to signals that indicate they are inside a host cell

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16
Q

what are the two modes in bacterial swimming

A

swim forward

tumble

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17
Q

how does a change in mode occur in taxis

A

altering direction of rotation of flagellum

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18
Q

what does anticlockwise rotation cause

A

smooth swimming

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19
Q

what does clockwise rotation cause

A

induces tumbling

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20
Q

what happens when polar flagellum in anticlockwise rotation if change the direction of rotation

A

cell moves backwards and induces turning cell starts to reorientate
once reorientated will change rotation again and swim in new direction

21
Q

what happens when peritrichous flagellum in anticlockwise rotation if change the direction of rotation

A

cell moves backwards
flagella unbundle = unstructured, induces turning change direction, totally random
get reorganised

22
Q

what happens to the bacteria after tumbling

A

bacteria randomly re-initiates forward movement

23
Q

how does taxis allow movement in chosen direction

A

bacteria capable of swimming towards an attractant or away from a repellent
frequency of running and tumbling is altered by environmental signals

24
Q

when is straight running favoured

A

is more of the attractant than previously sensed then the cells is heading in the right direction

25
Q

when is tumbling favoured

A

less of the attractant than previously sensed then the cells is heading in the wrong direction

26
Q

what does gradual drift towards attractant cause

A

‘biased random walk’

27
Q

how do bacteria respond to attractant stimuli

A

head towards

28
Q

how do bacteria respond to repellent stimuli

A

head away

29
Q

how do bacteria respond to neutral stimuli

A

ignore

30
Q

how do bacteria respond to chemical stimuli

A

chemotaxis

31
Q

how do bacteria respond to light stimuli

A

phototaxis towards lioght

32
Q

how do bacteria respond to gas stimuli

A

oxygen

aerotaxis

33
Q

how do bacteria respond to magnetic field stimuli

A

magnetotaxis

34
Q

what are the two ways to determine is you’re going in right direction when sensing chemicals immediately next to you

A

Spatial sensing

“Memory” sensing

35
Q

how do bacteria sense difference in chemical conc along their length

A

Bacteria are generally ~ 1 µm long
can’t sense chemical concentration differences along their length
must use a “Memory” method

36
Q

how is taxis controlled - regulation of swimming

A

using a set of sensory and regulatory proteins

Directly controls motor rather than changing gene expression

37
Q

what does control of taxis require

A

two components

A and B

38
Q

where is A component located

A

cell surface

39
Q

where is B component located

A

in cytoplasm

40
Q

what is A component

A

MCP = Methyl-accepting Chemotaxis Protein

sensor protein which responds to stimulus

41
Q

what is B component

A
  1. CheA/CheY = phosphor transfer system in cytoplasm
  2. CheY = induces switching of motor direction
  3. CheZ = system reset
42
Q

what occurs in control of taxis

A

stimulus outside, detect something like
signal transferred to Che A on inside, becomes phosphorylated
phosphate group transferred to Che Y = Che Y-P
Che Y-P induces a tumble, motor change
Che Z removes Che Y-P to Che Y, lets motor to return to CCW rotation

43
Q

where is C component

A

Alsp located in cytoplasm

44
Q

what occurs in C component

A 
CheR = methylating protein that modifies MCP
CheB-P = removes methyl groups
45
Q

what occurs in control of taxis when interact with attractant

A

remember have sensed attractant
Che R add methyl groups to MCP inside, get it to give signal to Che A needs more attractant
Methylated – need more molecules to change shape (desensitised)
need to reset system – use Che B
Che A deliver a phosphate to Che B
Che B-P made will start removing methyl groups

46
Q

what is memory sensing

A

compare the concentration that there is now with what was sensed previously

47
Q

what is needed for memory sensing

A

need chemical gradient along the length of the body

48
Q

what is spatial sensing

A

‘head’ end indicates there’s more chemical next to it than next to the ‘tail’ end of the cell

Physiology of Microbes (21 decks)

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