Identification and characterization of the Bacillus subtilis spoIIP locus

Abstract

We have identified an additional sporulation gene, named spoIIP, in the region of the Bacillus subtilis chromosome located immediately downstream of the gpr gene (227 degrees on the genetic map). A null mutation of spoIIP arrests sporulation at an early stage of engulfment (stage IIii), a phenotype similar to that already described for spoIID and spoIIM mutants. This gene encodes a 401-residue polypeptide, which is predicted to be anchored in the membrane, most of the protein being localized outside the cytoplasm. The spoIIP gene is transcribed from a promoter located in the interval between the gpr and the spoIIP reading frames. This promoter has the structural and genetic characteristics of a sigma E-dependent promoter. Transcription of spoIIP is abolished by a mutation in spoIIGB, the gene encoding sigma E, and can be induced during exponential growth in cells engineered to produce an active form of sigma E. Plasmid integration-excision experiments leading to the formation of genetic mosaics during sporulation indicate that as with SpoIID and SpoIIM, SpoIIP is required only in the mother cell. Disruption of spoIIP had little or no effect on the expression of sigma F- and sigma E-controlled regulons but inhibited transcription from sigma G-dependent promoters and abolished transcription from promoters under the control of sigma K. We propose that, together with SpoIID and SpoIIM, the SpoIIP protein is involved in the dissolution of the peptidoglycan located in the sporulation septum.