Bacterial Motility L10 Flashcards
which bacteria are usually non-motile
cocci
which bacteria are usually motile
bacillus and spiral cells
what does motility require
cell surface structures
how is bacterial motility distinguished
brownian motion
is gonorrhea motile
round cocci cell motile
how is bacterial movement regulated
environmental stimuli
- induction of movement
- direction of movement
what are the forms of bacterial motility
swarming
twitching
gliding
what is the name for bacteria with a single flagellum at 1 pole
monotrichious
what is the name for bacteria with a cluster at one pole
lophotrichious
lopho = tuft, multiple hairs
what is the name for bacteria with a single/cluster at both poles
amphotrichious
what is the name for bacteria with even distribution over surface
petritrichious
what is trichious
hair
how can flagellae be seen
too thin for light microscope
need electron micrograph or staining to make the flagellae thicker
how long are flagellae
at least as long as cell
what makes up the flagellum
filament
hook
basal body
what is the filament function in the flagellum
act as a propeller
what is the hook function in the flagellum
connects filament to motor
what is the basal body function in the flagellum
motor to turn whole flagellum round
what do the rings do in the flagellum structure
acts as washers
where is the basal body
spans cytoplasmic membrane and outer membrane
what does the basal body do
forms a specialised type of secretion complex
acts as a secretion pore, allow flagellum to be made in the cell and pass out so filament can be made outside
what is the gram negative bacteria flagellum like
basal body has 3 rings connected by a rod:
- SM ring embedded in cytoplasmic membrane
- P ring interacts with peptidoglycan layer
- L ring interacts with outer membrane
what is the gram positive bacteria flagellum like
basal body consists of SM ring and rod
no L ring
P ring much thicker as not got outer membrane just a thick layer of peptidoglycan
what happens once the basal body is formed
subunits for the hook assembled on outside of cell
what does the hook do for movement in cell
acts as an articulation joint to allow narrow helix to form during rotation
produces a tight spiral - good for powering cells forward
what is added to the Hook
end of hook defined by HAPs hook associated proteins
proteins put on end
what are the hook associated proteins used for
prevent it being a leaky pore, select movement
how is the flagellum assembled
basal body at bottom
rings on top
motor surrounds the proteins of the basal body
Flagellin added to the distal end (furthest away from the surface of the cell)
HAP2
how does the flagellin pass out of the cell, and its growth
cell through the hook
Passed HAPs
Flagellin added to the distal end (furthest away from the surface of the cell)
HAP2 form cap, controls addition of new flagellin subunits as grows
how are flagellum made
cells continually renew flagellum
where are the motor proteins located
below and around the SM ring
how does the cell have energy to move
energy for rotation of flagellum comes from cellular proton motive force (needs ATP)
how does the motor turn
H+ ions pass through periplasm into motor proteins into cell
one of the subunits of the motor proton = one turn of the motor ring
like an electrostatic meter
where are sheathed bacteria
found in spirochetes
located between cell wall and outer sheath
attached to one end of organism
how does the sheathed bacteria move
axial filaments turned, whole cell turns creating a corkscrew movement through liquid
when are swarmer cells made
Triggered to turn from swimmer to swarmer due to torque
If motor clicks round and something stops flagellae turning, knows on surface not liquid, makes torque
If flagella cant turn = torque (stress) knows not in a liquid medium, so turn into swarm cell
what is the difference between a swarmer cell and a swimmer
swarmer cells – increase massively the number of flagellae they make and become much longer, become multinucleate
what happens in swarmer cell process, what causes long swarmer cells
elongate, copy nucleic acid, at end of process cell division – if inhibit the cell division without inhibiting other = long swarmer cells
what do swarmer cells look like when moved on agar
rings from centre out
can swarmers convert back into swimmer cells
go back into liquid phase and torque stop, turn back into swimmer cells – completely reversible
examples of bacteria with twitching motility
Pseudomonas bacteria (gram -ve rod) Neisseria gonococcus (gram -ve coccus)
what is required for twitching motility
polar type 4 (fimbriae) pili
- fine hair like structures (6nm x 1-10um) formed from pilin protein
where does twitching motility occur
on surfaces
adhesion role to surfaces and host cells (virulence)
how do cells move when twitching motility
in intermittent or ‘jerky’ manner either singly or small aggregates
what are specialised pili for
plasmid transfer in conjugation
how is the pilus assembled
proteins at interface of cytoplasmic membrane and outer membrane, control assembly of flagellum
subunits brought into cytoplasmic membrane, sucked up into the PilQ complex – controls their assembly
pool of subunits in periplasmic space, can pulled on anytime to extend the pilus
pilus built outwards
what subunits make up the pilus
polymerisation ofPilA protein
pilus disassembly
unlike flagellum process is reversible (two way system)
need to continually add subunits to the pilus and pull them out and put somewhere – need to be in the pool
what causes the movement in twitching motility
movement induced by retraction of pilus
pili extended out is tight, starts to retract pilus
move towards where attached
what does twitching motility look like on agar
spreading zones on edge of colony
edge of colony has “ground glass” appearance
what does twitching motility require
alternative sigma factor for expression
what are the three modes that require surface filament production
swarming
swimming
twitching
which bacteria was gliding first identified in
cyanobacteria
where does gliding motility occur
only occur on surfaces; relatively slow
what changes in cell when gliding motilityoccurs
no change in cell morphology BUT cells have specialised cell wall structures to secrete mucilage
how does gliding motility move cell
pili at one end pull cells in one direction (S engine)
A engine slime pushes
what is necessary for gliding motility - engine slime used to push forward
extracellular slime made by junctional pore complex
need S layer (crystalline protein encasing outer membrane)
how do some cells control direction movement
helical oscillin fibrils (grooved structures on top of S layer)
what energy does gliding motility require
membrane potential (energised membrane) not ATP
what controls rate of movement
rate of movement proportional to rate of mucilage secretion
where is the junctional pore complex and what occurs here
JPC spans entire Gram negative cell wall, seems to be actual site of slime secretion
what does the slime do in gliding motility
slime flows in tight contact with surface of oscillin fibrils and guides rotation of filament
how do cells move in gliding motility using the slime
grooves are set diagonally across the cell
pumping slime into grooves
creates rotational movement
oscilin fibrils not on all cells
oscilin helps them move forward
when want to change direction will change which pump they use
what does flagella mediated motility need
flagella assembly
what is swarming motility
surface induced change in cell morphology
what is twitching motility
uses pili rather than flagellae
what is gliding motility
mediated by slime production
what is surface spreading
requires secretion complex to secrete surfactant, allow the cells to spread out following
growth
what do Swarmer cells inhibit
cytokinesis step
what are sheathed bacteria similar to
flagella
