Suppression of defective-sporulation phenotypes by mutations in transcription factor genes of Bacillus subtilis

Abstract

Mutations in the Bacillus subtilis major RNA polymerase sigma factor gene ( rpoD/ crsA47) and a sensory receiver gene ( spoOA/ rvtA11) are potent intergenic suppressors of several stage 0sporulation mutations ( spoOB, OE, OF & OK). We show here that these suppressors also rescue temperature-sensitive sporulation phenotypes (Spo ts) caused by mutations in RNA polymerase, ribosomal protein, and protein synthesis elongation factor EF-G genes. The effects of the crsA and rvtA suppressors on RNA polymerase and ribosomal protein spo ts mutations are similar to those previously described for mutations in another intergenic suppressor gene rev. We have examined the effects of rvtA and crsA mutations on the expression of sporulation-associated membrane proteins, including flagellin and penicillin binding protein 5 ∗ (PBP 5 ∗). Both suppressorsrestored sporulation and synthesis of PBP 5 ∗ in several spoO mutants. However, only rvtA restored flagelli synthesis in spoO suppressed backgrouds. The membrane protein phenotypes resulting from the presence of crsA or rvtA suppressors in spoO strainssuggests that these suppressors function via distinct molecular mechanism. The rvtA and crsA mutations are also able to block the ability of ethanol to induce spoO phenocopies at concentrations of ethanol which prevent sporulation in wild type cells. The effects of ethanol on sporulation-associated membrane protein synthesis in wild type and suppressor containing strains have been examined.