Developmental and environmental regulatory pathways in alpha-proteobacteria.

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.