Actinophage 4C31 isolated from Streptomyces coelicolor A3(2), the only strain among actinomycetes for which a genetic map had been constructed, appears to be a typical temperate phage. After 4C31 infection, true lysogenic cultures arose which liberated phage and were immune to infection with homologous phage after repeated single-colony isolations and treatment with phage-specific antiserum. Clear-plaque (c) mutants were derived from q5C31 phage which failed to lysogenize sensitive cultures. Actinophage 45C31 has a temperature-sensitive stage of reproduction. A phage which reproduces with the same effectiveness at high (37 C) and low (28 C) temperatures has also been obtained. Heat-inducible (ct) mutants were isolated from this phage which were able to lysogenize sensitive cultures at 28 C but failed to do so at 37 C. Properties of ct mutants suggest that ct mutations involve a gene controlling maintenance of the lysogenic state in actinomycetes and synthesizing repressor, which may become heat-sensitive as a result of mutation. The occurrence of true lysogeny in actinomycetes was reported and the general method for the screening of lysogenic actinomycetes was described by Welsch (14). Many papers on various aspects of lysogeny in actinomycetes were published soon afterward. This interest was due to the fact that the most industrial cultures of antibiotic-producing actinomycetes were lysogenic ones. The distribution of lysogenic Streptomyces in collections of strains was studied, especially in relation to antibiotic production (4, 15). The spontaneous induction of phage liberation and the efficiency of various agents that induce phage liberation were also studied. The measure of spontaneous induction
S U M M A R Y
Recombinants between Streptomyces coelicolor ~3 ( 2 )and Streptomyces griseus ~r .15 were obtained using methods of hybrid construction. Recombinant RcgI, obtained from a cross between S. griseus and a S. coelicolor UF (SCPI-) strain, phenotypically resembled S. coelicolor UF strains and in crosses with a S. coelicolor NF donor strain produced recombinant progeny at a frequency of roo %. Recombinant Rcg3, like SCPI-carrying S. coelicolor strains, inhibited SCPI-strains of S. coelicolor and in crosses with a UF recipient strain of S. coelicolor generated recombinants at high frequency. In crosses between S. griseus and RcgI the frequency of recombinant formation was increased about roo-fold relative to crosses between S. griseus and S. coelicolor. Effective transfer of S. griseus and Rcg3 chromosomal markers into RcgI and S. coelicolor, respectively, indicated that S. griseus had donor properties.Studies of the ability of recombinants to support phage growth indicated that parental chromosomal fragments containing genes involved in control of phagereceptor formation and intracellular growth were present in the hybrids. Grisinproducing recombinants, capable of restricting phages attacking S. coelicolor and S. griseus, were obtained.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.