High-level transcription of the major Bacillus subtilis autolysin operon depends on expression of the sigma D gene and is affected by a sin (flaD) mutation.

Transcription of the major Bacillus subtilis autolysin gene (cwlB) was investigated. Deletion of the region upstream of the gene cluster lppX-cwbA-cwlB led to a loss of promoter activity. Primer extension analysis suggested that the cwlB operon is transcribed by E sigma D and E sigma A, the former transcripts being predominants at the exponential growth phase. Expression of the lppX-lacZ fusion gene was reduced by about 90% in a sigD-null mutant. A sin (flaD1) mutation caused a severe defect in transcription of the lppX-cwbA-cwlB operon. The sin (flaD1) mutation also reduced expression of a sigD-lacZ fusion gene constructed in the B. subtilis chromosome. Since the sigD-null mutant exhibits motility and autolysin deficiencies and filamentation, similar phenotypes in the sin (flaD1) mutant may be caused by reduction in expression of the sigma D protein.