[Auxotrophic mutants of the producer of the antibiotic mycoheptin Streptoverticillium mycoheptinicum]. / Auksotrofnye mutanty produtsenta antibiotika mikogeptina Streptoverticillium mycoheptinicum.

The lethal and mutagenic effects of N-nitrozo-N-methyl biuret (NMB), N-nitrozo-N-methyl urea (NMU) and UV light on Streptoverticillium mycoheptinicum, strains O883 and 852, were studied. The concentrations of NMB were 0.005, 0.1 and 0.25 per cent, the exposure time was 2, 4 and 6 hours. The concentration of NMU was 1 per cent and the exposure time was 1, 2, 3, 4 and 5 hours. The dose of UV light was 2000 erg/mm2. When the spores of Streptoverticillium mycoheptinicum, strain O883, were treated with NMB, the frequency of auxotrophic mutants increased from 0.63 to 3.4 per cent with an increase of the mutagen concentration from 0.05 to 0.25 per cent and the exposure time from 2 to 6 hours. More than 80 auxotrophic mutants were selected. When Streptoverticillium mycoheptinicum, strain 852, was treated with NMU, the frequency of auxotrophic mutants ranged from 0.5 to 2.4 per cent. Fifty-seven auxotrophic mutants were selected. The majority of the auxotrophic mutants selected with the use of NMB and NMU was unstable. Exposure of Streptoverticillium mycoheptinicum, strains 852, 10/69 Met and 54/100 Lys to UV light resulted in formation of groups of polyauxotrophic mutants.

[Obtaining a productive strain of Streptoverticillium griseocarneum var. bleomycini that yields the new antineoplastic antibiotic, bleomycetin]. / Poluchenie produktivnogo shtamma Streptoverticillium griseocarneum var. bleomycini, obrazuiushchego novyi protivoopukholevyi antibiotik bleomitsetin.

Selection of the organism producing bleomycin, a multicomponent antitumor antibiotic, was performed. The aim was the selection of a more active strain with preferable synthesis of component A5 (bleomycetin) of the bleomycin complex. Optimal variants of the conditions for mutagensis with UV light and gamma-rays in step-wise selection of the active strain were determined and a possibility of selecting analog-resistant mutants with the use of structural analogs of the metabolites participating in synthesis of the bleomycin molecule was studied. A mutant analog-resistant strain capable of supersynthesis of bleomycin A5 (bleomycetin) was selected, the biosynthetic capacity of Streptoverticillum griseocarneum var. bleomycini being increased at least 19 times.

[Postradiation effect of caffeine on the producer of mycoheptin, Streptoverticillium mycoheptinicum]. / Postradiatsionnoe vliianie kofeina na produtsent mikogeptina Streptoverticillium mycoheptinicum.

The modifying effect of caffeine on irradiated spores of Streptoverticillium mycoheptinicum, producing mycoheptin was found. Postradiation treatment of the strain O883: spores with caffeine resulted in decreased survival of the spores proportionally to the radiation dose increase and postradiation caffeine treatment. An increase in the frequency of the morphologically changed colonies, as well as the low and highly active variants with respect to mycoheptin production was observed. The effect may be explained by the fact that caffeine possibly inhibited the reparation process in the irradiated spores of the strain tested. The method of postradiation treatment of the spores of the mycoheptin-producing organism with caffeine which provided selection of highly active variants by the antibiotic production with the use of definite doses may be considered promising in selection of actinomycetes.

[Dependence of the lethal and mutagenic effect of mitomycin C and UV rays on the Streptoverticillium mucoheptinicum spore germination process]. / Zavisimost' letal'nogo i mutagennogo éffekta mitomitsina C i UF-luchei ot protsessa prorastaniia spor Streptoverticillium mucoheptinicum.

The lethal and mutagenic effects of the DNA-tropic antibiotic mithomycin C and UV-light on Streptoverticillium mycoheptinicum during the period of the spore replication were studied. The spores were more stable to the effect of the mutagens during DNA replication after 120 minutes of incubation. The mutagenic activity of mithomycin C and UV-light was closely connected with the quantitative changes in the genetic material of the pores. During DNA replication the rate of the morphological mutants was the highest. With respect to production of mycoheptin the spores were most mutable under the effect of mithomycin C during the period of DNA replication, while under the effect of UV-light they were most mutable at the lag-phase.