Phylogenetic and functional prokaryotic diversity in the Hoito-Gol mesothermal mineral spring (Eastern Sayan Mountains,Buryat Republic)

High-throughput sequencing was used for comparative analysis of microbial communities of the water and mat from the Hoito-Gol mesothermal mineral sulfide spring (Eastern Sayan Mountains, Buryat Republic). Activity of microbial communities was determined. While both spring biotopes were dominated by members of three bacterial phyla—Proteobacteria, Bacteroidetes, and Firmicutes—they differed drastically in the composition of predominant phylotypes (at the genus level). In the water, the organisms widespread in aquatic environments were predominant, mostly aerobic chemoorganotrophs of the genera Acinetobacter, Pedobacter, and Flavobacterium. In the microbial mat, the organisms actively involved in the sulfur cycle predominated, including sulfur-reducing bacteria Sulfurospirillum, sulfate-reducing deltaproteobacteria, sulfuroxidizing chemoautotrophic bacteria, anoxygenic phototrophic bacteria of the phyla Chloroflexi and Chlorobi, as well as purple bacteria belonging to the α-, ß-, and γ-Proteobacteria. Microbial mats of the spring exhibited higher phylogenetic diversity compared to high-temperature mats containing photosynthetic microorganisms.     

EFFECTS OF HUMAN ACTIVITIES ON STRUCTURE AND COMPOSITION OF WOODY SPECIES OF THE NOKREK BIOSPHERE RESERVE OF MEGHALAYA,NORTHEAST INDIA

Aims Our study was conducted in the Nokrek Biosphere Reserve (NBR) in the Garo hills districts of Meghalaya, Northeast India. Our aim was to assess the effects of human activities on plant diversity,population structure and regeneration.Methods We selected a representative 1.2 hm2 stand in both the core and buffer zones of NBR. Structure and composition were determined by randomly sampling square quadrats, population structure was assessed by determining age structure, and regeneration was assessed by measuring densities of seedling, sapling and adult trees.Important findings More woody species were recorded from the core zone than the buffer zone (87 vs. 81 species), and there were a large number of tropical, temperate, and Sino-Himalayan, Burma-Malaysian and Malayan elements, primitive families and primitive genera. The trees were distributed in three distinct strata,canopy, subcanopy and sapling. Subcanopy and sapling layers had the highest species richness (81％ -88％ ). Lauraceae and Euphorbiaceae were the dominant families in terms of the number of species, and a large number of families were represented by single species. Most woody species (57 ％ - 79 ％ ) were contagiously distributed and had low frequency ( ＜ 20％ ). Although stand density was high in the buffer zone, its basal area was low compared to the stand in the core zone. Low similarity and high β-diversity indicate marked differences in species composition of the stands. Shannon diversity index was high in both the stands, while Simpson dominance index was low. The diameter-class distribution for dominant species revealed that the most had a large number of young individuals in their populations. Preponderance of tree seedlings, followed by a steep decline in population density of saplings and adult trees, indicated that the seedling to sapling stage was the most critical in the life cycle of the tree populations. Most species (42 ％ - 48 ％ ) had no regeneration,25 ％ - 35 ％ had good/fair regeneration, and the rest had poor regeneration or reoccurred as immigrants.     

Aerobic methanotrophs from the coastal thermal springs of Lake Baikal

The number, activity, and diversity of aerobic methanotrophic bacteria in the sediments of three coastal thermal springs of Lake Baikal were analyzed. The average number of methanotrophs was 10³–10⁴ cells per 1 cm³ of sediment. The highest number of methanotrophs (10⁸ cells/cm³ of silt) and the highest potential rate of methane uptake [7.7 nmol CH₄/(cm³ day)] were revealed in sediments from the Sukhaya thermal spring. The methods of molecular ecology (DGGE, FISH, analysis of pmoA gene fragments) showed the predominance in most enrichment cultures of methanotrophs of type II, i.e., of the genera Methylocystis and Methylosinus. In only one enrichment culture (from the Sukhaya thermal spring), a type I methanotroph was revealed; its similarity to Methylococcus capsulatus Bath did not exceed 80%. These results demonstrate a widespread occurrence and high activity of the aerobic methanotrophic community in the coastal thermal springs of Lake Baikal.     

Aerobic methanotrophic communities in the bottom sediments of Lake Baikal

The results of the first methodical investigation into the aerobic methanotrophic communities inhabiting the bottom sediments of Lake Baikal are reported. Use of the radioisotopic method revealed methane consumption in 12 10- to 50-cm-long sediment cores. The maximum methane consumption rates (495-737 microl/(dm3 day) were recorded in sediments in the regions of hydrothermal vents and oil and gas occurrence. Methane consumption was most active in the surface layers of the sediments (0-4 cm); it decreased with the sediment depth and became negligible or absent at depths below 20 cm. The number of methanotrophic bacteria usually ranged from 100 to 1000 cells/cm3 of sediment and reached 1 million cells/cm3 in the regions of oil and gas occurrence. The 17 enrichment cultures obtained were represented mainly by morphotype II methanotrophs. Phylogenetic analysis of the enrichment cultures in terms of the amino acid sequence of the alpha subunit of the membrane-bound methane monooxygenase revealed the predominance of methanotrophs of the genus Methylocystis. The results obtained suggest the presence of an active aerobic methanotrophic community in Lake Baikal.     

Lipid Auxotrophy and the Effect on Lipid Composition of Entamoeba invadens*†

SYNOPSIS. A medium for the axenic cultivation of Entamoeba invadens has been developed. Serum, an essential constituent of conventional media, has been replaced by a mixture of albumin, unsaturated fatty acids, Tween, and cholesterol to control the lipid composition of the medium. Entamoeba invadens requires both cholesterol and unsaturated fatty acids for growth. The fatty acid composition of the phospholipids of the ameba reflects that of the medium to a great extent, especially with regard to the unsaturated fatty acids. The amount of membrane bounded cholesterol depends on the cholesterol concentration in the medium.     

Liver cytochrome P-450 system in rats with a varying susceptibility to the development of experimental alcoholism

The cytochrome P-450-dependent monooxygenase system of the liver was studied in laboratory noninbred male rats selected according to the intensity of their initial alcohol motivation and the dynamics of these parameters was followed up during 10-day alcoholisation. It was shown that in the animals inclined to the development of alcoholism the activity of the monooxygenase system (cytochrome P-450, B5; enzymes: aminopyrine N-demethylase, aniline p-hydroxylase, NADPH-cytochrome c-reductase) is higher than in the animals noninclined to the development of this disease. 10-day alcohol consumption in the free-choice situation between water and 15% ethanol solution did not change the parameters investigated. The only exception was NADPH-cytochrome c-reductase: its activity grew in both the groups of the animals by 40-75%.     

Bacterial processes of the methane cycle in the bottom sediments of Baikal lake

The activity of methanogenic and methanotrophic bacteria was evaluated in bottom sediments of Lake Baikal. Methane concentration in Baikal bottom sediments varied from 0.0053 to 81.7 ml/dm3. Bacterial methane was produced at rates of 0.0004-534.7 microliters CH4/(dm3 day) and oxidized at rates of 0.005-1180 microliters CH4/(dm3 day). Peak methane production and oxidation were observed in Frolikha Bay near a methane vent. Methane was emitted into water at rates of 49.2-4340 microliters CH4/(m2 day). Rates of bacterial methane oxidation in near-bottom water layers ranged from 0.002 to 1.78 microliters/(1 day). Methanogens and methanotrophs were found to play an important role in the carbon cycle through all layers of sediments, particularly in the areas of methane vent and gas-hydrate occurrence.     

Aerobic Methanotrophic Communities in the Bottom Sediments of Lake Baikal

The results of the first systematical investigation into the aerobic methanotrophic communities inhabiting the bottom sediments of Lake Baikal have been reported. Use of the radioisotopic method revealed methane consumption in 12 10- to 50-cm-long sediment cores. The maximum methane consumption rates (495–737 µl/(dm³ day) were recorded in sediments in the regions of hydrothermal vents and oil and gas occurrence. Methane consumption was most active in the surface layers of the sediments (0–4 cm); it decreased with the sediment depth and became negligible or absent at depths below 20 cm. The number of methanotrophic bacteria usually ranged from 100 to 1000 cells/cm³ of sediment and reached 1 million cells/cm³ in the regions of oil and gas occurrence. The seventeen enrichment cultures obtained were represented mainly by morphotype II methanotrophs. Phylogenetic analysis of the enrichment cultures in terms of the amino acid sequence of the α subunit of the membrane-bound methane monooxygenase (MMO) revealed the predominance of methanotrophs of the genus Methylocystis. The results obtained suggest the presence of an active aerobic methanotrophic community in Lake Baikal.__________Translated from Mikrobiologiya, Vol. 74, No. 4, 2005, pp. 562–571.Original Russian Text Copyright © 2005 by Gainutdinova, Eshinimaev, Tsyrenzhapova, Dagurova, Suzina, Khmelenina, Namsaraev, Trotsenko.