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ABSTRACT A locus containing a gene with homology to ccpA of other bacteria has been cloned from Streptococcus mutans LT11, sequenced, and named regM . Upstream of the regM gene, on the opposite strand, is a gene encoding an X-Pro dipeptidase, pepQ . A 14-bp palindromic sequence with homology to the consensus catabolite-responsive element sequence lay in the promoter region between the two genes. To study the function of regM , the gene was inactivated by insertion of an antibiotic resistance marker. Diauxic growth of S. mutans on a number of sugars in the presence of glucose was not affected by disruption of regM . The loss of RegM increased glucose repression of α-galactosidase, mannitol-1-P dehydrogenase, and P-β-galactosidase activities. These results suggest that while RegM can affect catabolite repression in S. mutans , it does not conform to the model proposed for CcpA in Bacillus subtilis.
Simpson et al. (Fri,) studied this question.