Taxonomic and ecophysiological characteristics of actinobacteria in soils of the dry steppe zone of the Selenga Highlands (Western Transbaikalia).

Arid habitats have recently attracted increasing attention in terms of biodiversity research and the discovery of new bacterial species. These habitats are among the target ecosystems suitable for isolating new strains of actinobacteria that are likely to produce new metabolites. This paper presents the results on the isolation of actinobacteria from soils of the dry steppe zone of the Selenga Highlands, the characterization of their taxonomic diversity, as well as ecological and trophic properties. The bacterial counts on ISP 4 medium ranged from 6.6 × 105 to 7.1 × 106 CFU/g. The highest bacterial counts were observed in the subsurface and middle horizons of the studied soils. 28 strains of Gram-positive bacteria represented by thin-branched mycelium, coccoid and bacilliform forms were isolated. According to the results of 16S rRNA gene analysis, the isolated strains were representatives of Streptomyces, Arthrobacter, Glycomyces, Kocuria, Microbacterium, Micromonospora, Nocardioides, Pseudarthrobacter, and Rhodococcus (Actinomycetota). One isolate that showed low 16S rRNA gene sequence similarity with previously isolated and validly described species was a new species of the genus Glycomyces. It was shown that all tested strains are mesophilic, prefer neutral or slightly alkaline conditions, have growth limits in the temperature range of 5-45 °C and pH 6-9. The optimal NaCl concentration for growth of most strains was 0-1 %. The strains under study were capable of utilizing a wide range of mono- and disaccharides and polyatomic alcohols as a carbon source. The isolated strains were capable of using both organic (proteins and amino acids) and inorganic (ammonium salts and nitrates) compounds as nitrogen sources. The examinations of extracellular enzymes showed that all isolates were capable of producing catalase and amylase; 78.6 % of the total number of isolates produced protease and lipase; 53.6 %, cellulase; and 28.6 %, urease. The data obtained expand current knowledge about the diversity of microbial communities in soils of the Selenga Highlands and also confirm the potential of searching for new actinobacteria species in these soils.

[Respiration and ion permeability of the inner membrane in rat "sodium" liver mitochondria]. / Dykhanie i ionnaia pronitsaemost' vnutrennei membrany "natrievykh" mitokhondrii pecheni krysy.

Ion permeability of internal membrane and a respiration in isolated rat liver mitochondria, further related to as "sodium ones", were studied following replacement of K+ ions for Na+ ones in the mitochondrial matrix. As compared with the control ("potassium mitochondria"), state 4 respiration in the sodium mitochondria, energized by succinate, was shown to be enhanced in KCl or sucrose media. Oxygen consumption rates in the sodium mitochondria, being in state 3 or stimulated by 2,4-dinitrophenol, were lower than rates for the control mitochondria. This effect was much pronounced in the sucrose medium. The coefficients, characterizing the distribution of 137Cs between mitochondria and the medium, were lower for the sodium mitochondria than for the control in the presence of 2.5 mM succinate and 10(-8) M valinomycin. In comparison with the control, a more extensive swelling for the sodium mitochondria was found, first, in the medium containing 25 mM K-acetate and 100 mM sucrose for succinate-energized mitochondria, and second, in the medium containing 125 mM NH4NO3 without mitochondrial energization. Changes disclosed in respiration, swelling and coefficients of 137Cs distribution for the sodium mitochondria are supposed to be caused by non-uniform effects of Na+ and K+ ions on the water structure of mitochondrial matrix, ion permeability of internal membrane, and the activity in oxidative phosphorylation enzymes.

[Vertical distribution of the saprophytic microflora in the southeastern portion of the Pacific Ocean]. / Vertikal'noe raspredlenie saprofitnoi mikroflory v iugo-vostochnoi chasti Tikhogo okeana.

Data pertinent to the distribution of saprophytic bacteria at various depths in the south-eastern region of the Pacific Ocean were analyzed by the method of multiple comparison. A map was constructed for the vertical distribution of the density of saprophytic microflora whose concentration in this region was lower than in other regions of the equatorial-tropical zone of the World Ocean. The incidence of saprophytic microflora was low in the surface layer of 0 to 25 m or 0 to 50 m. Five regions were outlined with a typical vertical distribution of bacterial population. A high density of bacterial population confined mainly to the layer of 25 to 300 m was observed in the region from 2 degrees s. lat. to 10 degrees s. lat., or south of 12 degrees s. lat. in water near the shore. A narrow layer with an elevated concentration of bacteria was found only at a depth of 50 to 75 m north of the equator. At a depth over 300 m, the incidence of bacteria in water was low in the whole water area; elevated bacterial concentrations were detected down to a depth of 1000 m only in the region of southern tropical divergence. West of this region, layers with a high density of bacterial population were found at a depth of 300 to 500 m and 1000 and 1500 m. The lowest concentration of saprophytes was registered in regions south of 20 degrees s. lat.