Under phosphate-deficient conditions, B. intermedius, B. pumilus, and B. thuringiensis secrete phosphohydrolases, including phosphomono-, phosphodiesterases, and guanyl-specific ribonucleases which cleave RNA molecules to nucleoside-3'-phosphatases. The enzymes are synthesized by phosphate-starved vegetative cells, which is not associated with sporulation. Using B. subtilis strains with mutation in the regulatory protein genes phoP and phoR, it was shown that these proteins regulate expression of B. intermedius, B. pumilus, and B. thuringiensis ribonuclease genes in B. subtilis cells. Genes of heterologous RNAses were activated in recombinant B. subtilis strains simultaneously with its own PHO regulon genes. Presumably a regulatory system homologous to B. subtilis two-component PhoP-PhoR signal transduction system functions in other representatives of the Bacillus genus
