[Isolation and characterization of Saccharopolyspora erythraea mutants, resistant to chloramphenicol]. / Poluchenie i kharakteristika mutantov Saccharopolyspora erythraea, ustoichivykh k khloramfenikolu.

Formation of chloramphenicol resistant (CMr) spontaneous and nitroso-ethyl-urea-induced mutants of S.erythraea, an organism producing erythromycin, was studied. The mutants differed by the level of the chloramphenicol resistance (10 to 40 micrograms/ml). Part of the chloramphenicol resistance mutations had a pleiotropic pattern. 63.8 per cent of the CMr mutants was characterized by the growth thermosensitivity and 18.9 per cent was characterized by the absence of the melanin production property. The antibiotic potency of 56 per cent of the CMr mutants was higher than that of the initial strain. In some of the CMr mutants the property of resistance to other antibiotics was changed. A higher resistance of some mutants to chloramphenicol correlated with their increased lincomycin resistance. It was shown that chloramphenicol induced resistance to kanamycin in S.erythraea 5. Such a property for the resistance induction was preserved in the spontaneous low CMr mutants while the high CMr mutants isolated after the culture exposure to the mutagen lacked it. The CMr S.erythraea phenotype was genetically instable. Two different amplifying DNA sequences (18 and 70-78 kb in size) were detected in the CMr mutant genome. The chloramphenicol resistance mutation was localized in the S.erythraea chromosome region restricted by markers ura1 and met1.

[Amplifying sequences in the Streptomyces coelicolor A3 (2) gene]. / Amplifitsiruiushchiesia posledovatel'nosti v genome Streptomyces coelicolor A3 (2).

The unstable feature of ristomycin resistance in S. coelicolor A3 (2) was studied. It was shown that the frequency of ristomycin-resistant derivatives was high in both chloramphenicol sensitive mutants and their resistant revertants. The 15- and 20-kb DNA sequences capable of amplifying were detected in the chloramphenicol resistant revertants. In the genomes of the studied strains they were represented by 50 and 40 copies, respectively.

[Genetic instability of the feature of streptomycin resistance in Streptomyces erythraeus]. / Geneticheskaia nestabil'nost' priznaka streptomitsinoustoichivosti u Streptomyces erythraeus.

The feature of streptomycin resistance in S. erythraeus, a culture producing erythromycin, is genetically unstable. Mutants sensitive to 0.03 mg/ml of streptomycin are formed in the initial streptomycin resistant strains at a rate of 0.04 per cent. It was shown possible to perform step-by-step selection for increasing streptomycin resistance (from 0.2 to 15 mg/ml) in the mutants producing and not producing erythromycin. The increase in the streptomycin resistance did not lead to a higher resistance to other aminoglycosides. Restriction analysis of the total DNA with the use of various endonucleases demonstrated that the increase in the resistance was not associated with amplification of DNA nucleotide sequences.

[Characterization of multiple changes of antibiotic resistance characters in Streptomyces coelicolor A3(2)]. / Kharakteristika mnozhestvennogo izmeneniia priznakov ustoichivnosti k antibiotikam u Streptomyces coelicolor A3(2).

Among mutants of Streptomyces coelicolor A3(2) studied which were sensitive to chloramphenicol (Cmls), strains sensitive to a number of antibiotics (ristomycin, tetracycline, polymyxin, lincomycin) amount of 46%. Antibiotic-sensitive mutants are capable to form different classes of resistant revertants with frequency varying from 10(-2) to 10(-6) in independent strains. Ristomycin-sensitive clones (Rims) have been found to occur with high frequency in Cmls strains and Cmlr revertants. Mutations mediating the Rims phenotype are mapped in a locus linked to the gene for resistance to chloramphenicol. The results obtained are discussed, in accordance with the notion about possible role of cml mutation in induction of secondary mutational changes in the genome of S. coelicolor A3(2).