Effects of 5-azacytidine on physiological differentiation of Streptomyces antibioticus

We studied the specificity of the effect of 5-azacytidine, a DNA-methylase inhibitor that impairs Streptomyces differentiation. We showed that this compound did not affect global DNA, RNA or protein biosynthesis in submerged cultures of S. antibioticus ETHZ 7451. Among individual proteins, enzymes such as alkaline phosphatase and intracellular protease were produced in similar amounts in the presence and absence of this compound. However, the production of extracellular protease was significantly inhibited. Also DNA-methyltransferases were inhibited, indicating that DNA methylation might be involved in the regulation of differentiation. By contrast, elevated levels of the antibiotic rhodomycin resulted when 5-azacytidine was added to the culture medium. In order to determine whether there was a correlation between sporulation and altered enzymatic activities, these activities were analysed in S. antibioticus submerged cultures. Among them, alkaline phosphatase and intracellular protease activities did not show a clear correlation with sporulation. However, high levels of extracellular protease were produced during septation of hyphae. This association between extracellular protease and sporulation suggests a specific inhibitory effect of 5-azacytidine, not only on spore formation, but also on physiological differentiation.