Induction of Bacillus subtilis sporulation by nucleosides: inosine appears to be sporogen.

Inosine completely reversed the selective inhibition of sporulation in Bacillus subtilis 168 caused bym-aminobenzeneboronic acid; guanosine and adenosine, but not xanthosine, partially reversed inhibition, whereas pyrimidine nucleosides were slightly effective. In addition, 0.005 to 0.025 mM inosine caused a four- to fivefold stimulation of sporulation of B. subtilis grown in minimal salts medium. Ultraviolet and infrared spectra and other physical and chemical properties of inosine were markedly similar to those of "sporogen," a previously described endogenous sporogenesis factor present in sporulating Bacillus species.