A histidine protein kinase homologue required for regulation of bacterial cell division and differentiation

Differentiation in the dimorphic bacterium Caulobacter crescentus results from a sequence of discontinuous, stage-specific events that leads to the production of a stalked cell and a new motile swarmer cell after each asymmetric cell division. As reported previously, pseudoreversion analysis of mutations in the pleiotropic developmental gene pleC identified three cell division genes: divJ, divK, and divL. We show here that one of these genes, divJ, encodes a predicted protein of 596 residues with an extensive hydrophobic N-terminal region and a C-terminal domain containing all of the invariant residues found in the family of bacterial histidine protein kinases. Our results also show that divJ is discontinuously transcribed early in the swarmer cell cycle during a period that coincides with the G1 to S transition. We propose that the DivJ protein is one member of a signal transduction pathway regulating the cell cycle and differentiation in Caulobacter and that protein modification by phosphorylation may play a central role in coupling developmental events to progress through the cell division cycle.