Lecture 8: Bacterial Cytoskeleton

Question 1

What are the 4 bacterial cytoskeletal elements?

Answer 1

1. Tubulin homologue - FtsZ
2. Actin homologue - MreB, Mbl proteins;
   ParM, MamK
3. Intermediate filaments - CreS
4. Molecular motors - not found in
   bacteria yet

Question 2

What is the role of MreB (and Mbl) in bacteria?

actin homologue

Answer 2

1. Cell growth and shape
2. mreB - mecillinam resistance gee identified in E. coli (rod)
3. mreB mutants = spherical
4. mbl mutants = deformed

Question 3

What happens to MreB in the presence of ATP or GTP?

Answer 3

1. Polymerases into filaments
2. Either form a continuous helical
   arrangement or dynamic patch
   arrangement

Question 4

How does MreB direct cell shape?

Answer 4

1. “Localizing proteins in a peptidoglycan
   factory”
2. MreC required for spatial organization of
   components of the peptidoglycan
   synthesis holoenzyme in the periplasm
3. MreB directs localization of precursor synthesis proteins in the cytosol

Question 5

How does MreB correlate with cell shape?

Answer 5

1. Spherical bacteria have be seen to have 
   no MreB gene
2. Rod bacteria do have MreB gene
    a. HOWEVER TWO GROUPS DO NOT:
        Agrobacteriuml Rhizobacterium
        Mycobacteriuml Corynebacterium

Question 6

Where in the cell does the wall grow from in rod shaped bacteria?

Answer 6

1. MOST cells: from the middle of the ‘long
   wall’ (MreB CABLES PRESENT)
2. EXCEPTIONS: at the poles (NO MreB
   PRESENT)

Question 7

What does FtsZ control (tubulin homologue)?

Answer 7

Cell division

Question 8

What is FtsZ polymerase dependent on?

Answer 8

GTP

Question 9

How is a FtsZ ring formed

Answer 9

assembly of numerous polymers using accessory proteins

Question 10

What is the process of binary fission?

Answer 10

1. growth/extension
2. chromosome replication
3. chromosome segregation
4. making the division site - crosswall
   formation
5. cell-cell seperationn

Question 11

How does FtsZ create cell division?

Answer 11

1. FtsZ polymerizes into ring structure in
   presence of GTP (GTPase activity)
2. FtsZ recruits other proteins (some
   involved in synthesis of new cell wall at
   division site)
3. Alongside extension at the long side of
   the cell in rod bacteria, extension also
   occurs in the middle of the division site
   using FtsZ as a scaffold

Question 12

How do spherical bacteria extend their cell wall?

Answer 12

Only occurs at the division site of the cell

Question 13

What is the role of intermediate filaments in bacteria?

Answer 13

1. CreS (IF)
2. CreS mutants lose the curved shape
3. CreS forms a filament alongside the
   curved shape of Caulobacter cells

Question 14

What is the role of ParM (actin homologue)?

Answer 14

1. Plasmid Positioning
2. (much like the mechanism used in
   eukaryotes using microtubules during
   mitosis)

Question 15

What is the role of MamK (actin homologue)?

Answer 15

controls organization of magnetite particles in magnetosomes