[Effect of a corrinoid on Methanosarcina barkeri DNA synthesis].

Methanosarcina barkeri is capable of synthesizing large amounts of corrinoids, compounds of the vitamin B12 group, although not cobalamin. In the present work, exogenous cobalamin was demonstrated to upregulate DNA synthesis in M. harkeri cell suspensions incubated under air. The effect is similar to the one in Propionibacterium freudenreichii cells, though less pronounced. The growth of the archaeon under anaerobic conditions was shown to be suppressed by cobalamin and 5,6-dimethylbenzimidazole. The data obtained suggest the presence of a corrinoid-dependent ribonucleotide reductase in the archaeon cells which provides for deoxyribose precursors for DNA biosynthesis independently of the presence of molecular oxygen in the medium. Growth suppression under anoxic conditions by cobalamin and 5,6-dimethylbenzimidazole may be due to a decrease in the concentration of factor III, a polyfunctional corrinoid dominating in M. barkeri cells.

[A positive effect of Propionibacterium freudenreichii on the growth of Saccharomyces cerevisiae during their cocultivation].

The growth pattern of Saccharomyces cerevisiae and Propionibacterium freudenreichii ssp. shermanii (P. shermanii; propionic acid bacteria, PABs) during cocultivation in liquid media depended on the ratio of the cells in the inoculum. An increase in the growth rate of S. cerevisiae was observed at a PAB to yeast ratio of approximately 3 : 1; higher ratios exerted adverse effects on yeast growth. The culture liquid of 18- to 24-h (young) cultures of PABs stimulated yeast growth. Although yeast growth-stimulating exometabolites of PABs were not high-molecular-weight compounds, they were thermolabile. When present in the medium at concentrations of up to 1.5%, the antimicrobial agent sodium propionate did not interfere with S. cerevisiae growth; however, it completely inhibited the growth of B. subtilis at a concentration of 0.2%.

[The aeration-dependent effect of vitamin B12 on DNA biosynthesis in Methylobacterium dichloromethanicum]. / Uchastie vitamina B12 v biosinteze DNK u Methylobacterium dichloromethanicum, zavisimoe ot intensivnosti aératsii.

The effect of vitamin B12 (cobalamin) on DNA biosynthesis in Methylobacterium dichloromethanicum was studied. When cultivated in media with methanol or dichloromethane, the bacterium produced approximately 10 micrograms corrinoids per g dry biomass, compared to about 7 micrograms/g when cultivated on ethanol or succinate. Exogenous adenosylcobalamin (AdoCbl) stimulated DNA biosynthesis in M. dichloromethanicum cells grown under poor aeration, the effect being mediated by AdoCb1-linked ribonucleotide reductase. In vitro studies showed that M. dichloromethanicum also has AdoCbl-independent ribonucleotide reductase. Under good aeration, exogenous AdoCbl had no effect on DNA biosynthesis, while hydroxyurea suppressed it. These data suggest that AdoCbl-independent ribonucleotide reductase, which is likely to be activated by oxygen, plays an important part in DNA biosynthesis when M. dichloromethanicum is cultured with good aeration, whereas AdoCbl-dependent ribonucleotide reductase is active under the conditions of poor aeration.

[Multiple functions of corrinoids in prokaryote biology]. / Mnozhestvennye funktsii korrinoidov v biologii prokarioticheskikh organizmov.

Data on more than 30 metabolic processes and biochemical reactions, involving corrinoids, which have been described in prokaryotes thus far, are reviewed. These pathways (central or specific, catabolic or anabolic) are inherent in bacteria and archebacteria of diverse phylogenetic lineages, comprising several physiological groups. Particular emphasis is placed on the role of corrinoid-dependent transmethylation in acetogenesis and methanogenesis and on the contribution of adenosylcobalamin in DNA metabolism.