Transcription of the nfrA-ywcH operon from Bacillus subtilis is specifically induced in response to heat

The NfrA protein, an oxidoreductase from the soil bacterium Bacillus subtil is, is synthesized during the stationary phase and in response to heat. Ana lysis of promoter mutants revealed that the nfrA gene belongs to the class III heat shock genes in B. subtilis. An approximate 10-fold induction at bo th the transcriptional and the translational levels was found after thermal upshock. This induction resulted from enhanced synthesis of mRNA. Genetic and Northern blot analyses revealed that nfrA and the gene downstream of nf rA are transcribed as a bicistronic transcriptional unit. The unstable full -length transcript is processed into two short transcripts encoding nfrA an d ywcH. The nfrA-ywcH operon is not induced by salt stress or by ethanol. A ccording to previously published data, the transcription of class III genes in general is activated in response to the addition of these stressors. Ho wever, this conclusion is based on experiments which lacked a valid control . Therefore, it seems possible that the transcription of all class III gene s is specifically induced by heat shock.