Five mutants of Streptomyces coelicolor having auxotrophic requirement for aromatic amino acids were mapped relative to closely linked genetic markers. Based on four-point reciprocal crosses mutants were found to map in at lea.st two locations. One mutant mapped between proA and hisC while three fell between argA and hisE. Another mutant mapped between hisC and hisE; however, its position relative to argA has not been determined.

Phenotypic analysis of the Aro mutants was undertaken. One mutant has a requirement for tyrosine and phenylalanine; one mutant has a requirement for all three aromatic amino acids, tryptophan, tyrosine, and phenylalanine; one mutant has a requirement for aromatic amino acids and para-aminobenzoic acid; and two mutants have a requirement for aromatic amino acids, para-aminobenzoic acid, and an undetermined requirement satisfied by 5μg/ml of yeast extract. None of the mutants were able to utilize quinic acid or shikimic acid in place of the aromatic requirements; however, the wild-type strain is able to utilize shikimic acid as a sole carbon source. Mutants having a tryptophan requirement were able to utilize anthranilic acid or indole in place of tryptophan.

Complementation tests based on analysis of heteroclones have shown that the five mutants affect at least three different genes. Two genes have been designated aroB and aroC; mutants in these genes did not complement aro-fl which defines aroA.