Regulation of the biosynthesis of secondary metabolites in Streptomyces galbus

: The effect of inhibiting and stimulating agents on the biosynthesis of secondary metabolites (actinomycin X and melanoid pigments) was studied in Streptomyces galbus as a function of the growth temperature. D-Valine was shown to inhibit actinomycin synthesis and to stimulate production of melanoid pigments. Tryptophan stimulated the synthesis of both actinomycin and melanoid pigments. The temperature of growth was found to regulate the biosynthesis of secondary metabolites by the culture. The organism synthesized actinomycin at 28 degrees C, but it switched to the production of melanoid pigments at 42 degrees C. This may be considered as a protective reaction of the organism to an increase in the temperature of the environment and in UV radiation which is possible under natural conditions as a consequence of temperature elevation. The paper presents a hypothetical scheme for the regulation of biosynthesis of actinomycin and melanoid pigments by temperature. According to the scheme, the culture synthesizes secondary metabolites from tryptophan to hydroxykynurenine via a general pathway which is then bifurcated: at 28 degrees C--through methylhydroxyanthranilic acid to actinocin to actinomycin; at 42 degrees C--through hydroxyanthranilic acid, o-aminophenol, pyrocatechol, and possibly, o-benzoquinone, to melanin.