In vitro synthesis of ribosomal RNA by Bacillus subtilis RNA polymerase

Two kinds of hybridization competition experiments show that Bacillus subtilis RNA polymerase synthesizes ribosomal RNA (rRNA) in vitro with B. subtilis DNA as a template. First, RNA synthesized in vitro competes with the hybridization of [(32)P]rRNA synthesized in vivo to the heavy strand of B. subtilis DNA. Second, unlabeled rRNA synthesized in vivo competes with the hybridization of [(3)H]RNA synthesized in vitro to denatured DNA or heavy-strand DNA, but not to light-strand DNA. The ability of RNA polymerase holoenzyme to synthesize rRNA in vitro is not lost after extensive purification. RNA polymerase core enzyme, however, which is missing the sigma factor, synthesizes little rRNA in vitro.RNA polymerase purified from wild-type sporulating cells synthesizes little rRNA in vitro, while the in vitro synthesis of rRNA by RNA polymerase from stationary phase cells of the sporulation-defective mutant rfr 10 is apparently unimpaired.