Genetic recombination in Streptomyces michiganensis DSM 40,015 revealed three genes responsible for the formation of melanin.

By UV and NTG mutagenesis numerous auxotrophic, antibiotic-resistant and melanin-negative mutants were isolated from Streptomyces michiganensis DSM 40,015 which proved to possess a efficient photoreactivation system. Using a mel- test strain with three auxotrophic markers and a antibiotic resistance for crosses with numerous prototrophic mel- strains three classes of mutants (melA, melB and melC) could be found. This classification was further supported by a series of crosses. The melC locus seemed to correspond to the melC locus of S. glaucescens which contains the tyrosinase structural gene.