Differential transcription of the bla regulatory region during induction of beta-lactamase in Bacillus licheniformis.

Induction of beta-lactamase (blaP) in Bacillus licheniformis involves the regulatory genes blaI (repressor), blaR1 (coinducer) and R2 (function unknown). Transcription of the bla genes during induction was followed by Northern hybridization. In the first 30 min 2.3-kb transcripts encoding blaI and blaR1 were present. Subsequently, blaP mRNA and short transcripts encoding only blaI accumulated and reached a peak at 1 h. All bla transcripts turn over rapidly. Active repressor is not required for the burst of blaI-blaR1 mRNA. The production of blaI-blaR1 mRNA, and thus of BlaR1, is probably controlled both at initiation of transcription and at a later step in its synthesis and degradation.