Regulation of four genes encoding small, acid-soluble spore proteins in Bacillus subtilis

Three genes ( sspH, sspL, and tlp) encoding new, minor small, acid-soluble proteins (SASP) unique to spores of Bacillus subtilis are expressed only in the forespore compartment during sporulation of this organism. The sspH and sspL genes are monocistronic, whereas tlp is the second gene in an operon with a second small orf, which we have termed sspN. The sspH and sspL genes are recognized primarily by the forespore-specific sigma factor for RNA polymerase, σ G; the sspN-tlp operon is recognized equally well by σ G and the other forespore-specific σ factor, σ F. Sequences centered 10 and 35 nt upstream of the 5′-ends of sspH, sspL, and sspN mRNAs all show homology to −10 and −35 sequences recognized by σ F and σ G, which are generally quite similar. Mutations disrupting the sspH, sspL, sspN-tlp, or tlp loci cause a loss of the appropriate SASP from spores, but have no discernible effect on sporulation, spore properties, or spore germination.