[Genetic characteristics of a new phage resistance trait in Streptomyces coelicolor A3(2)]. / Geneticheskaia kharakteristika novogo priznaka fagoustoichivosti u Streptomyces coelicolor A3(2).

Phage resistance was investigated in the system of Streptomyces coelicolor A3(2) and phi C31 actinophage. Resistance of A3(2) strain to phi C31 was shown to involve a novel mechanism responsible for the arrest of phage intracellular growth in the whole cell population. The phage resistance character designated Pgl+ (for "phage growth limiting") is determined by a gene located on the A3(2) chromosome. The gene (pgl) controls phage "modification" which results in an inability of phage to lyse lysogenize Pgl+ host. Instability of the Pgl+ character was revealed. Pgl+ strains segregate Pgl variants at a high frequency, the majority of Pgl strains reverting to the initial Pgl+ phenotype with the same high frequency. Reversible Pgl+ in equilibrium Pgl transitions are a common feature of A3(2) cell population.

[Plasmid SCP2 transfer by Streptomyces coelicolor A3(2) actinophages]. / Perenos plazmidy SCP2 aktinofagami Streptomyces coelicolor A3(2).

The ability of VP5 and phi c31 actinophages of Streptomyces coelicolor A3(2) to transfer plasmid SCP2 genes was tested. Infection with both phages led to formation of variants having the traits characteristics of plasmid bearing strains. The fertility properties of the variants suggested the presence of SCP2 in the autonomous state. Analysis of extrachromosomal DNA isolated from these variants demonstrated its identity with the plasmid DNA from the donor strain. Based on characteristics of the variants obtained, it was suggested that the whole SCP2 plasmid had been transferred by actinophages via general transduction.

[Genetic mapping and characteristics of the actinophage phi C31 deletion mutants of Streptomyces coelicolor A3(2) incapable of lysogenization]. / Geneticheskoe kartirovanie i kharakteristika deletsionnykh mutantov aktinofaga fi C31 Streptomyces coelicolor A3(2), ne sposobnykh k lizogenizatsii.

Actinophage phi C31 deletion c mutants with impaired ability to make repressor were genetically studied. Genetic crosses indicate that the c28 deletion mutant is situated with the c-region of the phi C31 genetic map. Based on the results of a qualitive test for recombination between several c mutants, a scheme of their order relative to deletion mutants was presented. The approximate distances between eight c mutants have been represented in units of the physical DNA map estimation. Genetic studies of actinophage lyg deletion mutants which cannot lysogenize sensitive cultures were carried out. Mutants failed to lysogenize upon mixed infection with lyg+ phages. The absence of the effect of lyg+ gene in trans suggests that lyg deletions cause a structural defect in an integration site of the phage. Preliminary data on alignment of lyg positions on physical and genetic maps of phi C31 phage have been obtained. According to evidence from genetic crosses, lyg mutation has been located in the right half of the phi C31 genome.

[Physical mapping of Streptomyces coelicolor A3(2) actinophage DNA. I. Location of the c-region of actinophage phiC31]. / Fizicheskoe kartirovanie DNK aktinofagov Streptomyces coelicolog A3(2). I. Lokalizatsiia c-oblasti aktinofaga phiC31.

Mutants of temperate actinophage phi C31 Streptomyces coelicolor A3(2) having an increased resistance to chelating agents (sodium EDTA and sodium citrate) were isolated. Most of these mutants were not able to lysogenize sensitive cultures (c-mutants). DNA molecules of four c-mutants resistant to chelating agents were shown to be deleted by electron microscopy of DNA heteroduplexes. The four deletions were located in the central region of phi C31 DNA molecule. The deleted segment of 1000 base pairs common for molecules of all c-mutants is located in a region 47,2--49,9% and indicates the position of c-region on the physical map of phi C31 actinophage. The size of the region containing delections of all analyzed c-mutants is 1700 base pairs. The c-region on the heteroduplex map was oriented in relation to the known genetic map of phi C31.

[Genetic characteristics and genome structure of Streptomyces coelicolor actinophages]. / Geneticheskaia kharakteristika i struktura genomov aktinofagov Streptomyces coelicolor.

Actinophage phi C31 of Streptomyces coelicolor A3 (2) and two novel temperate actinophages phi C43 and phi C62 isolated from strains of blue actinomycetes group are homoimmune, serologically and functionally related. DNA molecules of phages phi C31, phi C43 and phi C62 have cohesive ends; sizes of DNAs of these phages and some mutants have been determined. The extent of homology between the DNAs of three phages is 93-96% as shown by heteroduplex analysis. The regions of non-homology are of a deletion-insertion type and of approximately 1500 base pairs in the length. Location of deletions in DNAs of mutant phages phi C31 vd and phi C31 c5 has been shown. Structural modifications in phage dnas have been found only to occur in the right part of molecules. Heteroduplex maps have been constructed for all phages studied.

[Determination of Streptomyces coelicolor A3(2) resistance to erythromycin]. / Determinatsiia ustoichivosti Streptomyces coelicolor A3(2) k éritromitsinu.

Resistance to erythromycin is genetically unstable in strains of Streptomyces coelicolor A3(2). The frequent loss of resistance as well as reversion of sensitive variants to the original unstable resistance phenotype excluded the possibility that plasmid elimination is involved. The spontaneous frequency of occurrence of sensitive clones was 0.14 to 1.5%, the rate of reversion ranging from 1.10(-6) to 1.10(-8). Resistance to erythromycin has been mapped on the chromosomes of two S. coelicolor A3(2) derivatives in different sites: between markers adeC (v 10) and ArgA1 in the strain A617, between pheA1 and SCP1 in the strain S18. It is suggested that genetic instability of erythromycin resistance determinants having chromosomal location is due to transposition of genetic material.

Construction and properties of hybrids obtained in interspecific crosses between Streptomyces coelicolor A3(2) and Streptomyces griseus Kr-15.

Recombinants between Streptomyces coelicolor A3(2) and Streptomyces griseus Kr-15 were obtained using methods of hybrid construction. Recombinant Rcg1, 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 strin produced recombinatn progeny at a frequency of 100%. Recominant Rcg3, like SCP1-carrying S. coelicolor strains, inhibited SCP1-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 100-fold relative to crosses between S. griseus and S. coelicolor. Effective transfer of S. grieseus and Rcg3 chromosomal markers into Rcg1 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 phage-receptor formation and intracellular growth were present in the hybrids. Grisin-producing recombinants, capable of restricting phages attacking S. coelicolor and S. griseus, were obtained.

Characterization of temperate actinophage phi C31 isolated from Streptomyces coelicolor A3(2).

Actinophage phiC31 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 phiC31 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 phiC31 phage which failed to lysogenize sensitive cultures. Actinophage phiC31 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.