Deletion and amplification of DNA sequences in melanin-negative variants of Streptomyces reticuli

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Abstract
The sporulating wild type of Streptomyces reticuli produces the pigment melanin. Though the ability to synthesize tyrosinase is frequently lost, it was demonstrated, that the structural gene coding for this enzyme is not located on the extrachromosomal DNA of the wild type strain or melanin-positive variants. Melanin negative variants were found to have lost this gene and to contain amplified nucleotide sequences within their genomes.