ROLE AND REGULATION OF BACILLUS-SUBTILIS GLUTAMATE-DEHYDROGENASE GENES

The complete Bacillus subtilis genome contains two genes with the pote ntial to encode glutamate dehydrogenase (GlutDH) enzymes. Mutations in these genes were constructed and characterized. The rocG gene proved to encode a major GlutDH whose synthesis was induced in media containi ng arginine or ornithine or, to a lesser degree, proline and was repre ssed by glucose. A rorG null mutant was impaired in utilization of arg inine, ornithine, and proline as nitrogen or carbon sources. Thc gudB gene was expressed under all growth conditions tested but codes for a GlutDN that seemed to be intrinsically inactive. Spontaneous mutations in gudB that removed a 9-bp direct repeat within the wild-type gudB s equence activated the GudB protein and allowed more-efficient utilizat ion of amino acids of the glutamate family.