Characterization of a prokaryotic SMC protein involved in chromosome partitioning

smc of Bacillus subtilis encodes a homolog of eukaryotic SMC proteins involved in chromosome condensation, pairing, and partitioning. A null mutation in B. subtilis smc caused a temperature-sensitive-lethal phenotype in rich medium. Under permissive conditions, the mutant had abnormal nucleoids, similar to 10% of the cells were anucleate, and assembly of foci of the chromosome partitioning protein SpoOJ was altered. In combination with a null mutation in spoOJ, the smc mutation caused a synthetic phenotype; cell growth was slower and similar to 25% of the cells were anucleate. Our results demonstrate that the B. subtilis Smc protein, like its eukaryotic counterpart, plays an important role in chromosome structure and partitioning.