1. Getting organized – how bacterial cells move proteins and DNA
Martin Thanbichler and Lucy Shapiro
Nature Reviews, 2008
Anna Buch

2. Model systems for bacterial cell biology
E. coli: history, genetic tools, physiology
B. subtilis: cell differentiation, large size
C. crescentus: cell division, synchonizable
mobile
sessile
Box 1

3. Assembly of stationary protein complexes
Diffusion and capture
Mother cell
SpoIVB
SpoIIQ
Septal membrane
Phagocytosis-like
uptake
Figure 1

4. Assembly of stationary protein complexes
Targeted membrane insertion
SpoIVB
SpoIIIAH
SpoIIQ
Figure 1

5. Assembly of stationary protein complexes
Targeted membrane insertion
Shigella flexneri:
facultative intracellular pathogen
IcsA: outer membrane protein, N-term is exposed to host cytoplasm
IcsP: Protease that cleaves off IcsA
Steinhauer et al., Mol Microbiol : ; Pollard & Cooper, Science :

6. Dynamic protein scaffolds and cell shape: Bacterial actin-like cytoskeleton
Bundles of two or more protofilaments.
Figure 2

7. MreB dynamics in C. crescentus
MreB cables
Spiral like during growth
Ring-like during cell division
Figure 2

8. Architecture of MreB cables
B. subtilis, FRAP of GFP-Mbl
Figure 2; Carballido-Lopez & Errington, Dev Cell :19-28.

9. Regulation of cell-wall biosynthesis
B. subtilis
Peptidoglycan (PG)
synthetic machinery
PG-hydrolase subunit
CW binding subdomain
MreB homologues: MreBH and Mbl
LytE: peptidoglycan hydrolase
Carballido-Lopez et al., Dev Cell :

10. Role of MreC in bacterial morphogenesis
DAPI
C. Crescentus
PBC (penicillin-binding protein):
involved in peptidoglykan synthesis
Divakaruni et al., PNAS :

11. Crescentin C. crescentus: In-vitro assay creS::Tn5 -> no crescentin
creS::Tn5 + creS ->crescentin on plasmid
In-vitro assay
His-CreS filaments,
EM negative stain
Ausmees et al., Cell :

12. Plasmid segregation
Actin superfamiliy member (type II partitioning system)
Walker ATPase (type I partitioning system)
Tubulin homologue

13. Plasmid segregation by actin-like proteins
Plasmid R1 of E. coli
Figure 3

14. Plasmid segregation by Walker-type ATPases
Walker A cytoskeletal ATPase (WACA)
Plasmids F and pB171 of E. coli
Adapted from Lim et al., PNAS :

15. Plasmid segregation by a tubulin homologue
TubZ: B. thuringiensis serovar israelensis (pBtoxis)
E.coli, expressing TubZ-GFP, FRAP, time in sec
Model proposes treadmilling
Larsen et al., Genes Dev :

16. Arrangement of chromosomal DNA
Figure 4, Viollier et al., PNAS :

17. Divisome: Bacterial cell-division apparatus
Rod-shaped bacterium (e.g. E. coli)
Z-ring: FitsZ filaments
Allard & Cytrynbaum PNAS :145-50; Erickson, PNAS :

18. Division-site placement: The Min system
minCDE operon:
MinD: WACA family
MinCD-complex: inhibit FtsZ-ring formation
MinE: represses MinCD activity
“Fail-safe mechanism”: nucleoid occlusion
B. subtilis: Noc
E. coli: SlmA
Figure 5

19. Division-site placement: The MipZ system
MipZ: ATPase, inhibits FtsZ-polymerization
ParB: chromosome partitioning protein
parS: cluster of sites, 15 kb away from ori

20. Conclusions Tubulin filaments: Actin cables: WACA ATPases:
cell-division apparatus, plasmid segregation
Actin cables:
DNA partitioning, cell-shape determination, protein localization
WACA ATPases:
DNA segregation, cell-division plane

21. Outlook Positioning of proteins at cell poles
TipN
Peptidoglycans
Cardiolipin -> ProP
Biochemical assembly mechanisms
Actin homologues
Tubulin homologues
WACA ATPases

22. Thank you for your attention!