PHYSICAL AND FUNCTIONAL-CHARACTERIZATION OF THE BACILLUS-SUBTILIS SPOIIM GENE

The spoIIM locus of Bacillus subtilis is the most recently discovered of six genetic loci in which mutations can prevent the synthesis of a normal asymmetric septum or prevent migration of the septal structure to engulf the forespore compartment of the sporangium. Ultrastructure studies of a spoIIM mutant confirmed a block prior to the completion o f engulfment. Introduction of a spoIIM mutation into a panel of strain s containing lacZ fusions belonging to different regulatory classes al lowed us to determine that the spoIIM gene product is required for the efficient expression of genes transcribed by sigma(G)-associated RNA polymerase but is not required for the expression of sigma(F)-controll ed genes, including spoIIIG, which encodes sigma(G). The results of co mplementation studies, gene disruption analysis, and DNA sequencing re vealed that the spoIIM locus contains a single sporulation-essential g ene encoding a polypeptide with a predicted molecular mass of 24,850 D a. The predicted spoIIM gene product is highly hydrophobic and very ba sic, and it does not exhibit significant homology to sequence files in several major data bases.