STUDIES ON THE GENETICS OF ANTIBIOTIC FORMATION: THE INDUCTION OF ANTIBIOTIC-FORMING MUTANTS IN ACTINOMYCETES

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Abstract
Seven actinomycetes[long dash]Streptomyces albosporeus, S. albus, S. cellulosae, S. flaveolus, S. griseus (a non-streptomycin producer), S. violaceus, and S. viridochromogenus[long dash]were selected on the basis of their having either no or only trace antibiotic activity against Micrococcus lysodeikticus, Escherichia coli, or both. The cultures were X-rayed, or treated with ultraviolet light in some cases, and large populations of each tested for the presence of antibiotically active mutants. Active mutants were found in all but 2 of the cultures, indicating that probably most actinomycetes can be induced to form antibiotically-active mutants. Active mutants were present at a frequency of from 0.01 to 1.9%. Many were types probably not capable of survival in nature. One mutant from the inactive S. griseus ATC 3326 formed either streptomycin or a closely related antibiotic. Mutants obtained from a single parent culture often differed from one another in antibacterial spectra, suggesting that mutants forming diverse, qualitatively different antibiotics could be induced to form from a single parent strain. The significance of these findings in relation to other metabolic products of microorganisms is discussed.