Bacillus subtilis DegU acts as a positive regulator for comK expression

Bacillus subtilis ComK plays a critical role in competence development. We report that B. subtilis degR, a positive regulator for exoenzyme production, is negatively regulated by overproduced ComK caused by a mecA null mutation. To identify a positive regulator for comK expression in the mecA background, mutations that allowed the degR gene to be expressed were screened in Tn10 transposon insertion mutants. As a result, we identified degU insertion mutations as those having such a property. The degU mutation reduced comK-lacZ expression in a competence medium in both the wild-type and mecA cells in sporulation and competence media. These results indicate that the degU gene product acts as a positive regulator for comK expression even under the condition where the negative regulation of comK by MecA is released.