Motility Regulation L11 Flashcards
(48 cards)
what is bacterial motility
control of gene expression and adaptation to the environment
what must be achieved for flagellum components to be produced in correct order
temporal gene expression
what is the internal structure of flagellum like
genes required for assembly of each part of the flagellum need to be produced in a specific order
what is RNA polymerase holoenzyme like
consists of six protein subunits
Core enzyme (five subunits)
Sigma factor
what does the sigma factor bind to in transcription
-10 and -35 sequences in bacterial promoters and identifies the beginning of a gene
what does sigma 28 control production of
Structural genes for flagellin production
what prevents the structural flagellin genes being expressed
not expressed until basal body is complete
where is sigma 28 in cell
σ 28 is made continuously by the cell but is bound to an ANTI-sigma factor protein (FlgM)
what happens when basal body is complete
FlgM is exported from cell
σ 28 released and induces expression of the structural genes
what causes temporal gene expression
Mechanism ensures that flagellin is made after the basal body is formed
Results in correct temporal gene expression
what are the steps that occur during temporal gene control of flagellum assembly
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
what is flagellin
surface antigen
H antigen
what is the benefit of variable flagellum
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
what os E.coli O:157 H:7
Flagellin is H antigen flagellin variant is 7
O:157 is numbered variant of LPS
what do many pathogens do to prevent detection
many pathogens switch OFF flagellin genes in response to signals that indicate they are inside a host cell
what are the two modes in bacterial swimming
swim forward
tumble
how does a change in mode occur in taxis
altering direction of rotation of flagellum
what does anticlockwise rotation cause
smooth swimming
what does clockwise rotation cause
induces tumbling
what happens when polar flagellum in anticlockwise rotation if change the direction of rotation
cell moves backwards and induces turning cell starts to reorientate
once reorientated will change rotation again and swim in new direction
what happens when peritrichous flagellum in anticlockwise rotation if change the direction of rotation
cell moves backwards
flagella unbundle = unstructured, induces turning change direction, totally random
get reorganised
what happens to the bacteria after tumbling
bacteria randomly re-initiates forward movement
how does taxis allow movement in chosen direction
bacteria capable of swimming towards an attractant or away from a repellent
frequency of running and tumbling is altered by environmental signals
when is straight running favoured
is more of the attractant than previously sensed then the cells is heading in the right direction
