L31: Tactic Behaviour

Question 1

How does chemotaxis happen and who does it

Answer 1

myxobacteria

1. the swarms detect the concentration of nutrients, lipids and prey cells.
2. when they detect prey it causes rippling behaviour, the rippling behaviour increases as the concentration of prey decreases
3. depending on the macromolecules detected, they respond differently for example WT mucoid colonies of S.melitoli are susepcitble but non mucoid mutants arent

Question 1

What is predataxix

Answer 1

Detection of concentration of prey cells?

Question 2

Explain flagellar motion in chemotaxis

Answer 2

the goal is movement of cells towards the attractant and away from repellant, this is accomplished via flagellar motion

CCW rotation => uniform movement from the helical bundle = run
CW rotation => random => disorientation = tumble

Question 3

Give an example of chemotaxis and not chemotaxis

Answer 3

movement must be towards attractant, if its moving towards inert object then its not chemotaxis

Question 4

What is a fruiting body and who does it

Answer 4

myxobacteria
repsonse to starvation where the population collectively desires its starving which illicits a stress response

Question 5

How do fruiting bodies form

Answer 5

Individual cells will stop growing and come together to form the fruiting body => leads to cell-cell communication and differentiation => some cells autolyse

the resources are pooled together to form the body and myxospores, the myxospores will be dispersed so it can leave law nutrient areas

Question 6

Explain how the starvation is sensed

Answer 6

starvation of a.a is sensed ar ribosomes => activates RelA enzyme which is the catalyst

1. RelA synthesised pppGpp and ppGpp when cells are starving
2. after [threshold] of pppGpp is achieved it means there is true starvation => stringent response
3. the pppGpp will accumulate in cells and produce Signal A
4. SignalA will accumulate to a threshold which will trigger the next set of signals

Question 7

What is signal A made of, disucss concentration, what does it allow and lead to

Answer 7

it is produced by the starving cells via conversion of protein into peptides + amino acids

in this form, its diffusable, membrane permeable and detectable by all cells

concentration is relative to pop density

allows population to make collective cell density dependay developmental changes

at [high] it leds to aggregation, fruiting body formation, pooling of resources and conversion of vegetative cells into myxospores

Question 8

What must the cell moniter during a fruiting body formation

Answer 8

1. cell density
2. timing and devleopmental events
3. tactic movement events
4. developmental autolysis/spore formation
5. 3D spatial orientation

Question 9

But why is the fruitng body essential

Answer 9

Formation of a fruiting body allows for pooling of resources, via autolysis, and raising of myxospores for better dispersion

Question 10

How is autolysis and sporulation

Answer 10

phospholipid ==>

Glucosamine cell wall component stimulates phopholipase to degrade phospholiipids

this leads to glyceral => pptd breaks down => sporulation (50% of survivors)

also leads to AMI the autolysis signal => 65%-90% cells lyse => nutrients released to survivors

Question 11

What are myxospores

Answer 11

tough shell

able to resist a lack of nutrients + harsh conditions

survive for years

Question 12

What is territoriality why do this

Answer 12

produce extracellular factors that inhibit other myxobacteria

This allows distance to be maintained to other fruiting bodies of other species

many strains in one fruiting body => fewer spores

helps to ensure monoclonal fruitng bodies and no fruiting bodies with >1 species