[USAGE OF FUMARATE BY SULPHATE-REDUCING BACTERIA DESULFOMICROBIUM SP. CrR3 AND DESULFOTOMACULUM SP].

Sulphate-reducing bacteria Desulfomicrobium sp. CrR3 and Desulfotomaculum. sp. are able to use fumarate as electron donor and acceptor. When they use fumarate as an electron acceptor succinate accumulates in the medium. If fumarate serves as electron donor, minor amounts of citrate, isocitrate and acetate are detected except succinate. In the case of simultaneous introduction of fumarate, SO4(2-) and Cr2O7(2-), the last inhibits usage of fumarate and SO4(2-).

[Synergistic effect of rib80 and hit mutations on riboflavin biosynthesis and iron transport in the yeast Pichia guilliermondii]. / Sovmestnoe vliianie mutatsii rib80 and hit na biosintez riboflavina i transport zheleza u drozhzhei Pichia Guilliermondii.

Mutant strains of the yeast Pichia guilliermondii, carrying both rib80 and hit mutations in a haploid genome, were derived from previously obtained strains with defective rib80 or hit genes, exerting negative control of the riboflavin biosynthesis and iron transport in Pichia guilliermondii. The double mutant rib80hit strains exhibited an increased level of riboflavin biosynthesis and higher activities of GTP cyclohydrolase and riboflavin synthetase. Iron deficiency caused an additional increase in riboflavin overproduction. These results suggest the synergistic interaction of the rib80 and hit mutations. A combination of both mutations in a single genome did not affect iron assimilation by the cells: ferrireductase activity, the rate of 55Fe uptake, and the iron content in cells of the double mutants remained at the level characteristic of the parent strains.

[The cloning and expression of the gene for beta-galactosidase from Candida pseudotropicalis yeasts in Saccharomyces cerevisiae cells]. / Klonirovanie i ékspressiia gena beta-galaktozidazy drozhzhei Candida pseudotropicalis v kletkakh Saccharomyces cerevisiae.

The gene of beta-galactosidase of lactose-assimilating yeast Candida pseudotropicalis was cloned in pG2 and pBG2-3 hybrid shuttle vectors and expressed in Saccharomyces cerevisiae laboratory strains under the control of own promoter. The plasmids were able to replicate autonomously with relative stability in transformants of baker's yeasts. The availability of glucose or lactose in the medium influenced the recombinant plasmid stability and the expression of the cloned gene. A number of experiments have shown that the LAC+ phenotype in pG2-transformed Saccharomyces cerevisiae was due to the expression of the Candida pseudotropicalis lactose permease gene that is probably located in SaIG1/XhoI DNA fragment about 4.3 kb long. Southern hybridization experiments showed that LAC(+)-transformants of Saccharomyces cerevisiae contained both autonomously-replicative, and integrative pG2 plasmid.

[The cloning and expression of the beta-galactosidase gene of Candida pseudotropicalis yeasts in Escherichia coli cells]. / Klonirovanie i ékspressiia gena beta-galaktozidazy drozhzhei Candida pseudotropicalis v kletkakh Escherichia coli.

The gene encoding the beta-galactosidase of the yeast Candida pseudotropicalis was cloned on YEp13 shuttle vector as the XhoI-fragment of chromosomal DNA of about 9.5 kb. SalGI-fragment of 7.5 kb with the beta-galactosidase gene was subcloned from the pG2 hybrid plasmid obtained into the pBR322 plasmid and then shortened to give 5.2 kb via deletion on XhoI site. This plasmid constructed was designated pBG2-1. In DNA/DNA hybridization studies the appearance of one XhoI-fragment and seven EcoRI-fragments in DNA C. pseudotropicalis hybridized to the DNA cloned fragment and the absence of hybridization to DNA Escherichia coli were shown. The beta-galactosidase activity of cells of transformants of E. coli was lower than the activity of prototrophic strain. The beta-galactosidase biosynthesis in transformants was insignificantly induced by lactose and IPTG and was not repressed by glucose.

[Flavin pool in Propionibacterium shermanii and the formation of corrinoids by bacterial cultures]. / Fond flavinov u Propionibacterium shermanii i obrazovanie korrinoidov kul'turami bakterii.

The content of flavins and vitamin B12 was studied in the cultures of Propionibacterium shermanii. The limited ability of propionic bacteria to synthesize 5,6-dimethylbenzimidazole, the nucleotide base in the true forms of vitamin B12, was found to be caused by a deficiency of the biogenetic precursor (riboflavin). Exogenous 5,6-dimethylbenzimidazole had no effect on the processes of flavinogenesis. In the absence of the nucleotide base, the yield of the true forms of vitamin B12 increased upon aeration of cultures which were grown for four days on an iron-deficient medium in the anaerobic conditions.