Self‐resistance of the nourseothricin‐producing strain Streptomyces noursei

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Abstract
The nourseothricin producer Streptomyces noursei is resistant to its own antibiotic in submerged as well as in surface culture. The strain shows no cross‐resistance to miscoding inducing aminoglycoside antibiotics. Cell free extracts of Streptomyces noursei inactivate nourseothricin by enzymatic acetylation. The pattern of cross‐resistance of Streptomyces noursei correlates well with the substrate specificity of the nourseothricin acetyltransferase. Furthermore, the acetyltransferase activity parallels the resistance level in nourseothricin‐producing strains and nonproducing mutants. The results suggest that the nourseothricin acetyltransferase is important in the self‐defence strategy of the nourseothricin‐producing strain.