Polar motility and cell cycle signaling pathways in Caulobacter crescentus

Caulobacter crescentus is a Gram-negative alpha-proteobacterium that divides asymmetrically genereting two distinct daughter cells for each cell cycle and that is used as model system to study basic mechanisms as cell cycle, division, polar morphogenesis and cell differentiation. Here we show that polarized factors, TipF and MopJ, and global signals, as second messengers c-di-GMP and ppGpp, regulate polar motility and cell cycle, respectively. During S-phase of the cell cycle TipF is recruted to the swarmer pole in a c-di-GMP dependent manner, where it leads the assembly of the flagellum, the structure in charge of motility. Bipolar MopJ, instead, enhances the signaling of CtrA, the master regulator of the cell cycle, through the inhibition of the DivJ/DivK pathway. Moreover MopJ genetically interacts with PtsP that inderectly induces the synthesis of ppGpp, reinforcing the CtrA output, through an unknown mechanism. So redundant parallel pathways regulate cell cycle fine tuning in C. crescentus