[A molecular version of a probability model of radiation injury of cells].

A molecular version of cell inactivation probability model has been proposed. Formal parameters of the model are interpreted. It has been shown that yeast cell inactivation regularities can be explained by DNA double-strand breaks processing during the postirradiation cell division.

[Genetic strains of Hansenula polymorpha].

Six centromeric linkage groups and four non-centromeric fragments are revealed in the genetic stocks of Hansenula polymorpha which were obtained by intratetrad breeding in several generations of two genetically different parental strains progeny. Fourteen nuclear markers are mapped, including auxotrophic mutations, mating regulation loci, determinants of sporulation and heat tolerance. Complex origin of the haploid genome of these stocks leads to affinity interactions and to 14 per cent increase in DNA content in haploid stocks, as compared with the parental strains.

[Growth characteristics of haploid and diploid Hansenula polymorpha yeasts on methanol in continuous culture].

The rate of growth and the yield of biomass of a Hunsenula polymorpha homozygous diploid strain ML-3 X ML-3 were nearly identical with those of the parent haploid culture ML-3. The two cultures were eliminated from the fermenter at D = 0.20 to 0.

[Hybridization of asporogenic strains of Hansenula polymorpha yeasts by protoplast fusion].

Intrastrain and interstrain hybrids of different ploidy were produced by the fusion of protoplasts of Hansenula polymorpha haploid and diploid strains. The diploid hybrids were found to be stable in contrast to the triploid and tetraploid hybrids. The instability of the triploid and tetraploid states in Hansenula polymorpha was expressed in the elevated frequency of spontaneous formation of auxotrophic markers and in the decreased content of DNA per cell in the course of storage.

[Mechanism of rapid postradiation recovery in yeasts].

Rapid postirradiation recovery of diploid yeast Saccharomyces cerevisiae is equally effective both in water and in a liquid nutrition medium. In the haploid strains, rapid recovery occurs more readily in the log phase than in the stationary phase of growth. In the diploid strains, rapid recovery is more effective in the log phase than in the stationary phase.

[Continuous cultivation of Hansenula polymorpha and Candida krusei on mixtures of methyl and ethyl alcohols].

The object of this work was to study whether it would be possible to cultivate together ther the methanol-assimilating yeast Hansenula polymorpha M-2 requiring biotin and thiamine for its growth and the vitamin-prototrophic yeast Candida krusei E-10 actively growing in a medium with ethanol, without vitamin addition to the medium. The growth of the mixed culture in a medium containing ethanol and methanol depended on the pH of the medium; the biomass yield was maximal at pH 3.5 which was the suboptimal value for H.

[Thiamine and biotin requirements of yeasts growing on methanol and ethanol].

The thiamine and biotin requirement of eight methanol assmilating yeast cultures belonging to four genera was studied during their growth in media containing methanol or ethanol. All the cultures, regardless of the species, required biotin during their growth in media containing either of the carbon sources. The cultures required thiamine (or its pyrimidine moiety) only when they utilized methanol.

[Quantitative analysis of yeast cell inactivation under the action of UHF radiation].

A particular case of the earlier suggested probability model of the action of electromagnetic irradiation on the cell is described. The model has been used for the quantitative analysis of inactivation forms and survival curves of yeast cells of different strains exposed by electromagnetic field of SHF-range. The results of calculation and experimental data show that the probability model is suitable for both qualitative and quantitative description of different cell responses to SHF-irradiation.