Promoter-independent catabolite repression of the Bacillus subtilis gnt operon

The mechanism underlying catabolite repression in Bacillus species remains unknown. A recent study of the promoter-independent catabolite repression of the gnt operon implicated a consensus sequence (ATTGAAAG) in catabolite repression in the genus Bacillus. The introduction of base-substitutions into the ATTGAAAG sequence in the chromosomal gnt operon affected catabolite repression of the gnt operon. Deletion analysis indicated that the ATTGAAAG sequence is probably part of a cis sequence necessary for the promoter-independent catabolite repression of the gnt operon. Furthermore, we subjected gnt transcripts synthesized with and without glucose to S1 nuclease and slot blotting analyses. The results indicated that the gnt transcripts decreased in the region (+93 to +203; +1, the transcription initiation nucleotide) only in the presence of glucose. Mechanisms underlying this promoter-independent catabolite repression are discussed.