Overlapping Promoters Transcribed by Bacillus Subtilis Sigma 55 and Sigma 37 RNA Polymerase Holoenzymes During Growth and Stationary Phases

A 471-base pair HindIII DNA fragment of Bacillus subtilis contains two overlapping promoters which are recognized in vitro by sigma 55- and sigma 37-containing RNA polymerase holoenzymes from B. subtilis. In vitro transcript analyses and S1 nuclease mapping experiments with in vivo RNA indicate that both enzymes initiate transcription from the same putative +1 site. Physiological studies with the promoter-containing DNA fragment inserted into the expression probe plasmid pCED6 and quantitative S1 nuclease mapping experiments with RNA isolated from various stages of growth indicate that expression from these overlapping promoters is greater during the early stationary phase than during growth. We propose that the cryptic gene controlled by these promoters is transcribed by the sigma 55 enzyme during growth and by the sigma 37 enzyme during early stationary phase.