Alphaproteobacteria is a class of gram negatives with remarkable characteristics. They often interact with or infect plants and animals. An alphaproteobacterium was the ancestor of mitochondria and a bacterium of this class is the most abundant species in the oceans. Moreover alphaproteobacteria often undergo to cellular differentiation and present a regulation of cell cycle (coordination between DNA replication, cell division and cellular differentiation) with same points of contact with eukaryotes. In the team Biondi, we aim to understand logic and principles of cell cycle regulation and asymmetrical cell division in two well-known model systems, Caulobacter crescentus and Sinorhizobium meliloti (see figure).
In Caulobacter crescentus, CtrA (response regulator of Two-Component systems) controls many important functions (motility, DNA methylation, cell division, chemotaxis, stalk and pili biogenesis) and blocks directly the origin of DNA replication. In our lab we investigate the mechanisms of CtrA phosphorylation by CckA and ChpT (Biondi et al., 2006, Nature) which is blocked by the DivJ-(PleC)-DivK module and c-di-GMP. We also investigate the regulation of transcription by CcrM-dependent genome methylation and GcrA (Fioravanti et al., 2013, PLOS Genetics). In Sinorhizobium CtrA also controls cell cycle but it also involved in nitrogen-fixing bacteroids differentiation (Pini et al., 2013, Mol Micro ; Pini et al., 2015, PLOS Genetics).
Finally using tools of systems biology, bioinformatics and synthetic biology we compare regulatory circuits in order to understand the evolution and the molecular mechanisms of bacterial cell cycle (Brilli et al., 2010, BMC Systems Biology).