Genetic studies of avermectin biosynthesis in Streptomyces avermitilis

A genetic recombination study of an industrial strain of Streptomyces avermitilis which produces avermectin is described. A genetic map has been constructed by analysis of haploid recombinants and linkage relationships of 16 marker loci. Fifteen avermectin-nonproducing mutants, produced by mutagenesis, were classified into two phenotypically different groups, of which one produced avermectin aglycon and the other was able to convert avermectin aglycon to avermectins. Two different mutants were found to map closely to each other.