Distinct Activities of Bacterial Condensins for Chromosome Management in Pseudomonas aeruginosa

Three types of structurally related structural maintenance of chromosomes (SMC) complexes, referred to as condensins, have been identified in bacteria. Smc-ScpAB is present in most bacteria, whereas MukBEF is found in enterobacteria and MksBEF is scattered over the phylogenic tree. The contributions of these condensins to chromosome management were characterized in Pseudomonas aeruginosa, which carries both Smc-ScpAB and MksBEF. In this bacterium, SMC-ScpAB controls chromosome disposition by juxtaposing chromosome arms. In contrast, MksBEF is critical for chromosome segregation in the absence of the main segregation system, and it affects the higher-order architecture of the chromosome by promoting DNA contacts in the megabase range. Strikingly, our results reveal a prevalence of Smc-ScpAB over MksBEF involving a coordination of their activities with chromosome replication. They also show that E. coli MukBEF can substitute for MksBEF in P. aeruginosa while prevailing over Smc-ScpAB. Our results reveal a hierarchy between activities of bacterial condensins on the same chromosome. [Display omitted] •P. aeruginosa possesses two condensins with distinct activities in chromosome management•MksBEF can promote chromosome segregation and long-range cis contacts in P. aeruginosa•P. aeruginosa condensin activities are functionally coordinated with replication•A functional hierarchy rules bacterial condensin activity on the same DNA molecule The three types of bacterial condensins show distinct activities for chromosome management in Pseudomonas aeruginosa. Lioy et al. show that while Smc-ScpAB mainly controls chromosome disposition inside the cell, the other two complexes favor cis contacts between chromosomal loci and support chromosome segregation. The results also reveal a hierarchy between different condensin activities.