Caulobacter crescentus

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Caulobacter crescentus is a free-living organism belonging to the proteobacteria alpha division. Its most distinctive feature is the existence of an asymmetric cell cycle, creating at each division cycle two cell types with distinct morphology and cellular fate. The swarmer cell possesses a flagellum and a chemotactic apparatus, and it is the form responsible for the dispersion of C. crescentus. This cell type is incapable of initiating the replication of the genetic material before it differentiates into a stalked cell. In order to do this, the swarmer cell must lose its flagellum, proteolytic cleave its chemotactic apparatus and initiate the stalk synthesis in the same pole where the flagellum used to be. Once the chromosome is duplicated, a new flagellum begins to be built in the pole opposite to the stalk. After the cytokinesis, two new daughter cells, one being flagellated and the other being stalked, are generated. The stalked cell is capable of immediately start DNA replication and progress to the next cell cycle. The main cellular differentiation global regulator in C. crescentus, CtrA, is responsible for the control of the major part of the differential expressed genes during the cell cycle. Besides this mechanism, cell compartment specific proteolysis and the dynamic localization of structural and regulatory proteins also play important roles in the cellular differentiation regulation in this organism.

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