Microbial movement – crawling, gliding and swimming

Question 1

In order to utilise nutrients

Answer 1

microorganisms need means of locomotion

Question 2

examples of locomotion

Answer 2

1) e.g. Chlamydomonas moving towards light – phototaxis
2) Dictyostelium cells aggregating – chemotaxis
3) Bacteria and eukaryotic cells migrating towards food sources - chemotaxis

Question 3

There are several models of how chemotaxis works (the same models hold for phototaxis as this like chemotaxis depends upon signal perception)

Answer 3

1) temporal model
2) spatial model
3) pseudospatial

Question 4

whats the temporal model?

Answer 4

assumes that a cell ‘remembers’ a concentration of signal at T0

Question 5

whats the spatial model?

Answer 5

assumes cells can determine the difference in concentration around themselves

Question 6

whats the pseudospatial model?

Answer 6

similar but depends upon the cell actively probing the environment e.g. with pseudopodia

Question 7

How does movement take place (crawling) in Dictyostelium ?

Answer 7

Movement takes place by successive elongation of the leading edge by extension of pseudopodia, combined with adhesion to a substrate surface

Question 8

Motion in Dictyostelium depends on…

Answer 8

Motion depends upon the combined effects of a pull from the front and a push from behind.

Question 9

Describe crawling in Dictyostelium

Answer 9

1) protrusion
2) adhesion
3) traction
4) de-adhesion/tail retraction
5) protrusion

Question 10

Describe the dynamic system of motility in dictyostelium

Answer 10

Actin reversibly polymerises so cytoskeleton is continuously formed and broken down

Question 11

Myosin also associates with …

Answer 11

… both the leading and lagging edges of the cell providing the force to move the cell

Question 12

An alternative model is that …

Answer 12

… cell movement is due to growth of membrane – but in the case of Dictyostelium this cannot account for speed of cells

Question 13

how is invasion of erythrocytes by Plasmodium accomplished ?

Answer 13

Both invasion of erythrocytes and movement along the matrix of cells in Plasmodium is accomplished by use of the actomyosin motor.

Question 14

Conformational change in …

Answer 14

… actin ratchets against actin filaments causing a force which provides forward movement

Question 15

Many bacteria move by …

Answer 15

… a ‘gliding’ motion.

Question 16

Many bacteria move by a ‘gliding’ motion

According to some research, how does this work?

Answer 16

Some research suggests attachment and contraction of Type IV pili is important in gliding in certain bacteria including Myxococcus and Clostridium

Question 17

Describe gliding movement

Answer 17

1. extension and attachment of type IV pilus
2. contraction moving cell towards attachment point
3. release of pilus and re-extension

Question 18

Eukaryotic cilia and flagella have …

Answer 18

…have an identical structure.

Question 19

Eukaryotic cilia and flagella have an identical structure. However, they…

Answer 19

…differ in their length.

Question 20

flagella and cilia consist of…

Answer 20

… an axoneme (2 microtubules) in the centre and 9 pairs of microtubules around the periphery (9+2 structure).

Question 21

Connections between the axoneme and the outer microtubules are by…

Answer 21

… nexins and dynein.

Question 22

Eukaryotic cilia and flagella consist primarily of …

Answer 22

… microtubules

Question 23

Movement of eukaryotic flagella and cilia is generated by …

Answer 23

… the slippage of one microtubule against another

Question 24

Movement of eukaryotic flagella and cilia is generated by the slippage of one microtubule against another.

as the microtubules are connected this results in …

Answer 24

… bending of the microtubule creating a ‘whiplash’ like motion.

Question 25

Slippage is caused by movement of ...

Answer 25

... dynein arms – on hydrolysis of ATP (energy)

Question 26

Slippage is caused by movement of dynein arms – on hydrolysis of ATP (energy) the dynein ...

Answer 26

... head moves towards the minus end of the microtubule causing a shift of one microtubule against another – so the energy dependent movement of the dynein head causes bending.

Question 27

the bacterial flagellum is made of...

Answer 27

... multiple molecules of flagellin.

Question 28

The flagellum is ...

Answer 28

... sinusoid and movement comes from the force imparted by it against liquid molecules in the media

Question 29

Each species has a ...

Answer 29

... characteristic wavelength

Question 30

The drive for the movement of the rotary motor associated with the bacterial flagellum is provided by...

Answer 30

... the flux of protons over a gradient.

Question 31

In Gram negative bacteria protons move from ...

Answer 31

... high concentration in the periplasmic space to low concentration

Question 32

what complex do protons move through in driving the rotary motor of bacterial flagella?

Answer 32

the Mot complex

Question 33

The movement of protons through the Mot complex (surrounding the basal body of the flagellum) ...

Answer 33

... drives rotation

Question 34

where is the Mot complex?

Answer 34

surrounding the basal body of the flagellum

Question 35

chemical energy is converted to ...

Answer 35

... kinetic energy

Question 36

for swimming bacteria, chemical energy is converted to kinetic energy via...

Answer 36

hydrolysis of ATP to ADP

Question 37

for bacterial flagella using a proton motive force, chemical energy is converted to kinetic energy by...

Answer 37

... the movement of protons

Question 38

Dead wood is a ...

Answer 38

... huge potential nutritional resource for animals

Question 39

Dead wood is a huge potential nutritional resource for animals – however animals lack the enzymes able to break down cellulose Termites accomplish this by ...

Answer 39

... utilising a protozoan called Mixotricha.

Question 40

Mixotricha itself is a ...

Answer 40

... eukaryote and also cannot produce cellulase

Question 41

Endosymbiosis with cellulase digesting bacteria enable ...

Answer 41

... Mixotricha to accomplish this, so providing the termite with food

Question 42

Myxotricha has other endosymbionts, including ...

Answer 42

... a mitochondrion and rod shaped bacteria adhered to its outside.

Question 43

Myxotricha also has an...

Answer 43

... ectosymbiont

Question 44

Myxotricha also has an ectosymbiont! What is embedded in its cell periphery ?

Answer 44

Thousands of spirochaete bacteria are embedded in its cell periphery.

Question 45

These spirochaetes have ...

Answer 45

... rotating flagella which provide the motive force by which Myxotricha moves around.