Isolation and characterization of a mutator strain of Streptomyces ambofaciens ATCC23877 exhibiting an increased level of genetic instability
In Streptomyces ambofaciens ATCC23877, 0.7% of pigment-defective mutants (Pig−) can be observed in the progeny of wild-type colonies. A mutator (Mut−) strain was isolated from the offspring of the wild-type strain. The Mut− strain produced colonies that sported nonpigmented papillae. Furthermore, the frequency of Pig− colonies obtained in the progeny of this strain was fivefold higher than in the wild-type strain. This strain showed the same level of sensitivity to ultraviolet light and mitomycin C as the wild-type strain. This Mut− phenotype was found to be reversible at high frequency (3 × 10−3). Genomic analysis using pulsed-field gel electrophoresis (PFGE) showed that the Pig− mutants arisen from the Mut− strain were less frequently rearranged (32% were deleted) compared with the mutants arising from the wild type (59% were deleted). Moreover, the Pig− papillae mutants possessed no visible rearrangement as revealed by PFGE analyses.Key words: Streptomyces, genetic instability, mutator strain, papillae.