Chromosome organization by a conserved condensin-ParB system in the actinobacteriumCorynebacterium glutamicum

AbstractHigher-order chromosome folding and segregation is tightly regulated in all domains of life. In bacteria, details on nucleoid organization regulatory mechanisms and function remains poorly characterized, especially in non-model species. Here, we investigate the role of DNA partitioning protein ParB and condensin complexes, two key players in bacterial chromosome structuring, in the actinobacteriumCorynebacterium glutamicum. Chromosome conformation capture reveals SMC-mediated long-range interactions around ten centromere-likeparSsites clustered at the replication origin (oriC). At least oneoriC-proximalparSsite is necessary for a reliable chromosome segregation. Using a combination of chromatin immunoprecipitation and photoactivated single molecule localization microscopy evidences the formation of distinct ParB-nucleoprotein subclusters in dependence ofparSnumbers. We further identified and functionally characterized two condensin paralogs. Whereas SMC/ScpAB complexes are loaded via ParB atparSsites mediating chromosomal inter-arm contacts like inBacillus subtilis, the MukBEF-like SMC complex MksBEFG does not contribute to chromosomal DNA-folding. Rather, the MksBEFG complex is involved in plasmid maintenance and interacts with the polaroriC-tethering factor DivIVA. These data complement current models of ParB-SMC/ScpAB crosstalk, while showing that some condensin complexes evolved functions uncoupled from chromosome folding.