[Distribution, diversity, and activity of sulfate-reducing bacteria in the water column in Gek-Gel Lake, Azerbaijan].

The distribution and activity of sulfate-reducing bacteria (SRB) in the water column of the alpine meromictic Gek-Gel lake were studied. Apart from traditional microbiological methods based on cultivation and on measuring the process rates with radioactive labels, in situ fluorescent hybridization (FISH) was used, which enables identification and quantification without cultivating organisms. The peak rate of sulfate reduction, 0.486 microg S/(l day), was found in the chemocline at 33 m. The peak SRB number of 2.5 x 106 cells/ml, as determined by the end-point dilutions method on selective media, was found at the same depth. The phylogenetic position of the SRB, as determined by FISH, revealed the predominance of the Desulfovibrio spp., Desulfobulbus spp., and Desulfoarculus spp./Desulfomonile spp. groups. The numbers of spore-forming Desulfotomaculum spp. increased with depth. The low measured rates of sulfate reduction accompanied with high SRB numbers and the predominance of the groups capable of reducing a wide range of substrates permit us to propose utilization of electron acceptors other than sulfate as the main activity of the SRB in the water column.

[Microbiological and isotopic-geochemical investigations of meromictic lakes in Khakasia in winter].

Microbiological and isotopic-geochemical investigations of the brackish meromictic lakes Shira and Shunet were performed in the steppe region of Khakasia in winter. Measurements made with a submersed sensor demonstrated that one-meter ice transmits light in a quantity sufficient for oxygenic and anoxygenic photosynthesis. As in the summer season, in the community of phototrophic bacteria found in Lake Shira, the purple sulfur bacteria Amoebobacter purpureus dominated, whereas, in Lake Shunet, the green sulfur bacteria Pelodictyon luteolum were predominant. Photosynthetic production, measured using the radioisotopic method, was several times lower than that in summer. The rates of sulfate reduction and production and oxidation of methane in the water column and bottom sediments were also lower than those recorded in summer. The process of anaerobic methane oxidation in the sediments was an exception, being more intense in winter than in summer. The data from radioisotopic measurements of the rates of microbial processes correlate well with the results of determination of the isotopic composition of organic and mineral carbon (delta13C) and hydrogen sulfide and sulfate (delta34S) and suggest considerable seasonal variations in the activity of the microbial community in the water bodies investigated.

[The biogeochemical cycle of methane in the coastal zone and littoral of the Kandalaksha Bay of the White Sea]. / Biogeokhimicheskii tsikl metana v pribrezhnoi zone i litorali Kandalakshskogo zaliva Belogo moria.

Microbiological and biogeochemical investigations of the processes of methane production (MP) and methane oxidation (MO) in the coastal waters and littoral of the Kandalaksha Bay of the White Sea were carried out. The studies were conducted in the coastal zones and in the water areas of the Kandalaksha Preserve, Moscow University White Sea Biological Station, and Zoological Institute (RAS) Biological Station in August, 1999, 2000, and 2001 and in March, 2001. The rate of CO2 assimilation in the shallow and littoral sediments was 35-27800 microg C/(dm3 day) in summer and 32.8-88.9 microg C/(dm3 day) in winter. The maximal rates of MP were observed in the littoral sediments in the zone of macrophyte decomposition, in local depressions, and in the estuary of a freshwater creak (up to 113 microl/(dm3 day)). The maximal level of MO was observed in the shallow estuarine sediments (up to 2450 microl/(dm3 day)). During the winter season, at the temperature of -0.5 to 0.5 degrees C, the MP rate in the littoral sediments was 0.02-0.3 microl/(dm3 day), while MO rate was 0.06-0.7 microl/(dm3 day). The isotopic data obtained indicate that the C(org) of the mats and of the upper sediment layers is enriched with the heavy 13C isotope by 1-4 per thousand as compared to the C(org) of the suspension, comprised on 33.5-34.3% of phytoplankton. A striking difference was found between the levels of methane emission by the typical littoral microlanscapes. In fine sediments, the average emission was 675 microl CH4/(m2 day), in the stormy discharge stretch sediments it was 1670 microl CH4/(m2 day), and under the stones and in silted pits, 1370 microl CH4/(m2 day). The calculation performed with consideration of the microlandscape areas with a high production allowed the CH4 production of 1 km2 of the littoral to be estimated as 192-300 1 CH4/(km2 day).

[Microbial sulfate reduction in sediments of the coastal zone and littoral of the Kandalaksha bay of the White sea]. / Protsess mikrobnoi sul'fatreduktsii v osadkakh pribrezhnoi zony i litorali Kandalakshskogo zaliva Belogo moria.

Microbiological and biogeochemical investigations of the coastal zone and the littoral of the Kandalaksha Bay of the White Sea were carried out. The material for investigations was obtained in the series of expeditions of the Institute of Microbiology, Russian Academy of Sciences, in August 1999, 2000, 2001, and in March 2003. The studies were conducted on the littoral and in the water area of the Kandalaksha Preserve, the Moscow University Belomorsk Biological Station, and the Zoological Institute Biological Station, Russian Academy of Sciences, Sediment sampling on the littoral was carried out in the typical microlandscapes differing in the sediment properties and macrobenthos distribution. The maximal sulfate reduction rate (SRR) was shown for the shallow part of the Chemorechenskaya Bay (up to 2550 micrograms S/(dm3 day)) and in the Bab'ye More Bay (up to 3191 micrograms S/(dm3 day)). During the winter season, at a temperature of -0.5-0.5 degrees C, the SRR in the sediments of the Kartesh Bay was 7.9-13 micrograms S/(dm3 day). In the widest limits, the SRR values varied in the sediment cores sampled on the littoral. The minimal values (11 mu]g S/(dm3 day)) were obtained in the core samples on the silt-sandy littoral. The littoral finely dispersed sediments rich in organic matter were characterized by high SRR values (524-1413 micrograms S/(dm3 day)). The maximal SRR values were shown for the sediments present within the stretch of decomposing macrophytes, in local pits at the lower littoral waterline, and in the mouth of a freshwater stream (51-159 mg S/(dm3 day)). A sharp difference in the level of H2S production in the type microlandscapes was shown. The average hydrogen sulfide production in finely dispersed sediments constituted 125 mg S/(m2 day); in stormy discharge deposits, 1950 mg S/(m2 day); in depressions under stones and in silted pits, 4300 mg S/(m2 day). A calculation made with regard to the area of microlandscapes with increased productivity shows that the daily H2S production per 1 km2 of the littoral (August) is 60.8 to 202 kg S/(km2 day), while the organic carbon consumption for sulfate reduction per 1 km2 of the littoral is 46 to 152 kg C(org)/(km2 day).

[Microbial metabolism of the carbon and sulfur cycles in Shira Lake (Khakasia)]. / Mikrobnye protsessy tsiklov ugleroda i sery v ozere Shira (Khakasiia).

Microbiological and biogeochemical studies of the meromictic saline Lake Shira (Khakasia) were conducted. In the upper part of the hydrogen-sulfide zone, at a depth of 13.5-14 m, there was a pale pink layer of water due to the development of purple bacteria (6 x 10(5) cells/ml), which were assigned by their morphological and spectral characteristics to Lamprocystis purpureus (formerly Amoebobacter purpurea). In August, the production of organic matter (OM) in Lake Shira was estimated to be 943 mg C/(m2 day). The contribution of anoxygenic photosynthesis was insignificant (about 7% of the total OM production). The share of bacterial chemosynthesis was still less (no more than 2%). In the anaerobic zone, the community of sulfate-reducing bacteria played a decisive role in the terminal decomposition of OM. The maximal rates of sulfate reduction were observed in the near-bottom water (114 micrograms S/(1 day)) and in the surface layer of bottom sediments (901 micrograms S/(dm3 day)). The daily expenditure of Corg for sulfate reduction was 73% of Corg formed daily in the processes of oxygenic and anoxygenic photosynthesis and bacterial chemosynthesis. The profile of methane distribution in the water column and bottom sediments was typical of meromictic reservoirs. The methane content in the water column increased beginning with the thermocline (7-8 m), and reached maximum values in the near-bottom water (17 microliters/l). In bottom sediments, the greatest methane concentrations (57 microliters/l) were observed in the surface layer (0-3 cm). The integral rate of methane formation in the water column and bottom sediments was almost an order of magnitude higher than the rate of its oxidation by aerobic and anaerobic methanotrophic microorganisms.

[Biogeochemical cycle of methane in the northwestern shelf of the Black Sea]. / Biogeokhimicheskii tsikl metana na severo-zapadnom shel'fe chernogo moria.

Seasonal investigations of methane distribution and rates of its oxidation and generation in the water column and sediments of the Black Sea northwestern shelf were carried out within the framework of the interdisciplinary projects "European River-Ocean Systems" (EROS-2000, EROS-21) and "Biogenic Gases Exchange in the Black Sea" (BigBlack) in August 1995, May 1997, and December 1999. Experiments that involved the addition of 14CH3COONa and 14CO2 to sediment samples showed the main part of methane to be formed from CO2. Maximum values of methane production (up to 559 mumol/(m2 day)) were found in coastal sediments in summer time. In winter and spring, methane production in the same sediments did not exceed 3.6-4.2 mumol/(m2 day). The delta 13C values of methane ranged from -70.7 to -81.8@1000, demonstrating its microbial origin and contradicting the concept of the migration of methane from cold seeps or from the oil fields located at the Black Sea shelf. Experiments that involved the addition of 14CH4 to water and sediment samples showed that a considerable part of methane is oxidized in the upper horizons of bottom sediments and in the water column. Nevertheless, it was found that, in summer, part of methane (from 6.8 to 320 mumol/(m2 day)) arrives in the atmosphere.

[Desulfacinum subterraneum sp.nov.--a new thermophilic sulfate-reducing bacterium isolated from a high temperature oil field ]. / Desulfacinum subterraneum sp.nov--novaia termofil'naia sul'fatvosstanavlivaiushchaia bakteriia, vydelennaia iz vysokotemperaturnogo neftianogo plasta.

A new thermophilic sulfate-reducing bacterium isolated from the high-temperature White Tiger oil field (Vietnam) is described. Cells of the bacterium are oval (0.4-0.6 by 0.6-1.8 microns), nonmotile, non-spore-forming, and gram-negative. Growth occurs at 45 to 65 degrees C (with an optimum at 60 degrees C) at NaCl concentrations of 0 to 50 g/l. In the course of sulfate reduction, the organism can utilize lactate, pyruvate, malate, fumarate, ethanol, salts of fatty acids (formate, acetate, propionate, butyrate, caproate, palmitate), yeast extract, alanine, serine, cysteine, and H2 + CO2 (autotrophically). In addition to sulfate, the bacterium can use sulfite, thiosulfate, and elemental sulfur as electron acceptors. In the absence of electron acceptors, the bacterium can ferment pyruvate and yeast extract (a yet unrecognized capacity of sulfate reducers) with the formation of acetate and H2. The G + C content of DNA is 60.8 mol %. The level of DNA-DNA hybridization of the isolate (strain 101T) and Desulfacinum infernum (strain B alpha G1T) is as low as 34%. Analysis of the nucleotide sequence of 16S rDNA places strain 101T in the phylogenetic cluster of the Desulfacinum species within the sulfate reducer subdivision of the delta subclass of Proteobacteria. All these results allowed the bacterium studied to be described as a new species, Desulfacinum subterraneum sp. nov., with strain 101 as the type strain.

[Microbial processes of carbon and sulfur cycles in lake Mogil'noe]. / Mikrobnye protsessy tsikla ugleroda i sery v ozere Mogil'nom.

In the beginning of summer 1999, complex microbiological and biogeochemical investigations of meromictic Lake Mogil'noe (Kil'din Island, Barents Sea) were carried out. The analysis of the results shows clearly pronounced vertical zonality of the microbial processes occurring in the water column of the lake. To a depth of 8 m, the total number and activity of microorganisms was limited by the relatively low content of organic matter (OM). In the upper part of the hydrogen-sulfide zone of the lake (beginning at a depth of 8.25 m), the content of particulate OM and the microbial number sharply increased. In this zone, the daily production of OM during anaerobic photosynthesis at the expense of massive development of colored sulfur bacteria reached 620 mg C/m2, which was twofold greater than the daily production of phytoplankton photosynthesis and led to a considerable change in the isotopic composition (delta 13 C) of the particulate OM. In the same intermediate layer, the highest rates of sulfate reduction were recorded, and fractionation of stable sulfur isotopes occurred. Below 10 m was the third hydrochemical zone, characterized by maximum concentrations of H2S and CH4 and by a relatively high rate of autotrophic methanogenesis. The comparison of the results obtained with the results of investigations of previous years, performed in the end of summer, shows a decrease in the intensity of all microbial processes inspected. An exception was anoxygenic photosynthesis, which can utilize not only the de novo formed H2S but also the H2S accumulated in the lake during the winter period.

[Microbiological processes at the interface of aerobic and anaerobic waters in the deep-water zone of the Black Sea]. / Mikrobiologicheskie protsessy na granitse aérobnykh i anaérobnykh vod v glubokovodnoi zone chernogo moria.

Chemical and key microbiological processes (assimilation of carbon dioxide, oxidation and formation of methane, and sulfate reduction) occurring at the boundary between the aerobic-anaerobic interface in the deep-water zone of the Black Sea were investigated. Measurements were taken at depths from 90 to 300 m at intervals of 5-10 m. The integral rate of the dark assimilation of carbon dioxide varied from 120 to 207 mg C/(m2 day) with a maximum at the boundary of cyclonic currents. The organic matter (OM) formed from methane comprised less than 5% of the OM formed from carbon dioxide. A comparison between the rates of methane oxidation and methane production suggests that methane that is oxidized at depths from 100 to 300 m was formed in deeper water horizons. The maximum rate of sulfate reduction (1230 mg S/(m2 day)) was observed in the western halistatic region, and the minimum rate (490 mg S/(m2 day)), in the eastern halistatic region. The average rate of hydrogen sulfide production measured at three deep-sea stations amounted to 755 mg S/(m2 day), or 276 g S/(m2 year).