SPO0J IS REQUIRED FOR NORMAL CHROMOSOME SEGREGATION AS WELL AS THE INITIATION OF SPORULATION IN BACILLUS-SUBTILIS

The spoOJ gene of Bacillus subtilis is required for the initiation of sporulation. We show that the sporulation defect caused by null mutati ons in spoOJ is suppressed by a null mutation in the gene located dire ctly upstream fi om spoOJ, soj (suppressor of spoOJ). These results in dicate that Soj inhibits the initiation of sporulation and that SpoOJ antagonizes that inhibition. Further genetic experiments indicated tha t Soj ultimately affects sporulation by inhibiting the activation (pho sphorylation) of the developmental transcription factor encoded by spo OA. In addition, the temperature-sensitive sporulation phenotype cause d by the ftsA279 (spoIIN279) mutation was partly suppressed by the soj null mutation, indicating that FtsA might also affect the activity of Soj. Soj and SpoOJ are known to be similar in sequence to a family of proteins involved in plasmid partitioning, including ParA and ParB of prophage P1, SopA and SopB of F, and IncC and KorB of RK2. spoOJ was found to be required for normal chromosome partitioning as well as for sporulation. spoOJ null mutants produced a significant proportion of anucleate cells during vegetative growth. The dual functions of SpoOJ could provide a mechanism for regulating the initiation of sporulation in response to activity of the chromosome partition machinery.