Transcription of the Bacillus subtilis gerK Operon, Which Encodes a Spore Germinant Receptor, and Comparison with That of Operons Encoding Other Germinant Receptors

Abstract

ABSTRACT The gerA , gerB , and gerK operons, which encode germinant receptors in spores of Bacillus subtilis , were transcribed only in sporulation, and their mRNA levels peaked initially ∼3 h before the initiation of accumulation of the spore's dipicolinic acid. After a rapid fall, levels of these mRNAs peaked again ∼5 h later. In one wild-type strain (PS832), gerA mRNA was the most abundant, with levels of gerB and gerK mRNAs ∼50% of that of gerA mRNA, whereas gerB mRNA was the most abundant in another wild-type strain (PY79). The synthesis of gerK mRNA in sporulation was abolished by loss of the forespore-specific RNA polymerase sigma factor, σ G , and induction of σ G synthesis in vegetative cells led to synthesis of gerK mRNA. SpoVT, a regulator of σ G -dependent gene expression, repressed gerK expression. The gerK promoter showed sequence similarities to σ G -dependent promoters, and deletion of elements of this putative promoter abolished gerK expression in sporulation.