Lecture 2- Flagella and swimming motility Flashcards
what is the lifecycle of a spore forming bacterium
stage 1: asymmetric cell division (DNA replicates, identical chromosomes pulled to opposite ends of the cell)
stage 2: septation (divides cell into two unequal compartments; forespore (prespore) and mother cell)
stage 3: mother cell engulfs the forespore (forespore surrounded by two membranes)
stage 4: formation of the cortex (thick layers of peptidoglycan form between the two membranes)
stage 5: coat synthesis (protein layers surround the core wall –> spore coat, exosporium) Ca+ and SASP accumulates in the core to stabilize DNA
stage 6: endospore matures (core is dehydrated to make it more heat stable)
stage 7 mother cell is lysed (mother cell disintegrates, mature spore is released)
what is the general structure of flagella?
hollow protein filaments
do flagella need to be stained?
yes! with flagella stain
what are the 4 types of flagella?
monotrichous
amphitrichous
lophotrichous
peritrichous
what is monotrichous?
single flagellum
what is amphitrichous?
flagella at opposite ends
what is lophotrichous?
multiple flagella in a single tuft
what is peritrichous?
flagella distributed around cell
what are the 3 components to flagellar structure?
filament
hook
basal body (motor)
what is the filament of a flagella?
rigid helical protein
composed of identical protein subunits called flagellin
what is the hook of a flagella?
flexible coupling between filament and basal body
what is the basal body of a flagella?
its a central rod that passes through a series of rings
what are the 4 rings apart of the basal body in the flagella?
L ring: LPS layer
P ring: peptidoglycan
MS ring: membrane
C ring: cytoplasm (associated with membrane)
what energy does the flagella use to turn?
proton motive force
how does the proton motive force work with flagellar movement?
gradient of protons across the cytoplasmic membrane high proton outside
low proton inside
most proteins form a channel that allows H+ to move into the cytoplasm, this provides the energy to turn the flagellum
how does the flagellum move?
turns counterclockwise like a propeller to drive the cell forward
what is required for flagellar synthesis?
several genes are required for flagellar synthesis and motility
in what order does the flagella grow?
MS ring is made first
other proteins and hook are made next
filament grows from tip
how do peritrichously flagellated cells move?
slowly in a straight line
how do polarly flagellated cells move?
more rapidly and typically spin around
what is gliding motility?
flagella independent motility that requires surface contact through glide proteins
what 3 mechanisms are apart of gliding motility?
excretion of polysaccharide slime (decreases slime)
type IV pili (used to help in motility)
gliding specific proteins
what is a taxis?
directed movement in response to chemical or physical gradients
what are the 5 specific types of taxis?
chemotaxis
phototaxis
aerotaxis
osmotaxis
hydrotaxis
what is chemotaxis?
response to chemicals
what does chemotaxis do?
responds to temporal (not spatial) difference in chemical concentration
how do chemotaxis move?
run and tumble
they have directed movement toward an attractant or away from a repellent
how is a chemotaxis a biased random walk?
goes in a straight line (run) when it feels its getting close to the attractant but every couple seconds it tumbles and faces another direction
how do chemotaxis know theyre attracted to something?
by chemoreceptors
what is an example of chemotaxis?
E. coli shows biased random walk toward glucose when there is a concentration gradient. the cell will exhibit a series of runs and tumbles, if it senses that the glucose is increasing/ close the tumble is delayed and the run lasts longer
does the run and walk ever stop?
no, even when right beside attractant, flagella never stop moving
how do you measure chemotaxis?
by inserting a capillary tube containing an attractant or a repellant in motile bacteria
can also be seen under a microscope
what is phototaxis?
response to light
what is aerotaxis?
response to oxygen
what is osmotaxis?
response to ionic strength
what is hydrotaxis?
response to water
