FIG. 3.
Influence of deletions on transcription of the sigB gene in S. epidermidis 1457 and its mutants. (A) Northern blot analysis with a sigB-specific probe. S. epidermidis 1457 displayed a 1.5-kb transcript. The σA-dependent transcript of the entire σB operon could not be detected under the conditions used. Mutants with a remaining sigB gene displayed transcripts of increased sizes corresponding to the erm insertion. In sigB-negative mutants, no transcripts were detected. (B) Northern blot analysis with an erm-specific probe. For all mutants, a weak transcript comprising only the erm gene was detected, indicating a weak terminator following the erm gene. In mutants with a remaining sigB gene, additional transcripts with sizes identical to those of transcripts for the sigB-specific hybridization (A) were observed. In mutants with an inactivated sigB gene, the major transcripts detected were only slightly larger than the erm transcript, indicating a strong terminator preceding the sigB gene closely downstream. The genetic maps for the mutants are shown in Fig. 2. wt, wild type.