[Frontiers in Bioscience 17, 1695-1714, January 1, 2012]

Developmental and environmental regulatory pathways in alpha-proteobacteria

Silvia Ardissone1, Patrick H. Viollier1

1Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland


1. Abstract
2. Introduction
3. Control of cell cycle
3.1. CtrA and cell cycle regulators
3.2. Regulation of CtrA proteolysis by the ClpXP complex: RcdA, CpdR and PopA
3.3. CtrA phosphorylation
3.4. Additional regulators of the CtrA pathway
4. PhyR, an anti-anti-sigma factor
5. Regulation of division and chromosome partitioning
5.1. FtsZ targeting factors
5.2. Fission of the cell envelope
5.3. Segregation and anchoring of the ori-region at the cell pole
6. Regulation of mucoidy and cell density
7. Conclusion
8. Acknowledgments
9. References


Spatial and temporal control of cell differentiation and morphogenesis plays a key role in prokaryotes as well as eukaryotes. This is particularly important for bacteria that divide asymmetrically, as they generate two morphologically and functionally distinct daughter cells. Several alpha-proteobacteria, including the aquatic, free-living Caulobacter crescentus, the symbiotic rhizobia and the plant and animal pathogens Agrobacterium and Brucella, have been shown to undergo asymmetrical division. C. crescentus has become a model system for the study of the regulatory networks, in particular the control of the cell cycle, the cytokinetic machinery, the cytoskeleton and the functions required for duplication and differentiation in general. As the bulk of these regulatory networks and functions is conserved in most alpha-proteobacteria, we recapitulate the recent advances in understanding these spatially and temporally controlled processes, focusing on cell cycle progression, DNA replication and partitioning, cell division and regulation of specific phenotypes that vary during the cell cycle or in the case of different lifestyles (like extracellular polysaccharide production) in C. crescentus and other alpha-proteobacteria.