Nature of the brown pigment and the composition of the phenol oxidases of Streptomyces galbus

: The culture of Streptomyces galbus ISP-5089 has a yellow-green colour caused by the accumulation of actinomycin X when it is grown in synthetic media at 28 degrees C; the colour turns dark-brown at 42 degrees C due to the synthesis of melanoid pigments. The population composition does not undergo any noticeable changes in that case, an no specific melanin-synthesizing mutants appear as a result of autoselection . The biosynthesis of actinomycin X (at 28 degrees C) and melanoid pigments (at 42 degrees C) is regulated by temperature. At 42 degrees C, L-DOPA oxidase is synthesized and laccase is activated; these two enzymes are involved in the synthesis of melanoid pigments. The organism does not has tyrosinase. The synthesis of melanoid pigments, when the mesophilic culture of S. galbus ISP-5089 is grown in the regime of superoptimal temperatures (42 to 47 degrees C), may be considered as a protective ecological reaction of the organism to unfavourable conditions of the environment.