[A microbiological study of an underground gas storage in the process of gas extraction].

The numbers of microorganisms belonging to ecologically significant groups and the rates of terminal microbial processes of sulfate reduction and methanogenesis were determined in the liquid phase of an underground gas storage (UGS) in the period of gas extraction. The total number of microorganisms in water samples from the operation and injection wells reached 2.1 x 10(6) cells/ml. Aerobic organotrophs (including hydrocarbon- and oil-oxidizing ones) and various anaerobic microorganisms (fermenting bacteria, methanogens, acetogens, sulfate-, nitrate-, and iron-reducing bacteria) were constituent parts of the community. The radioisotopic method showed that, in all the UGS units, the terminal stages of organic matter decomposition included sulfate reduction and methanogenesis, with the maximal rate of these processes recorded in the aqueous phase of above-ground technological equipment which the gas enters from the operation wells. A comparative analysis by these parameters of different anaerobic ecotopes, including natural hydrocarbon fields, allows us to assess the rate of these processes in the UGS as high throughout the annual cycle of its operation. The data obtained indicate the existence in the UGS of a bacterial community that is unique in its diversity and metabolic capacities and able to make a certain contribution to the geochemistry of organic and inorganic compounds in the natural and technogenic ecosystem of the UGS and thus influence the industrial gas composition.

[A microbiological study of an underground gas storage in the process of gas injection].

The liquid phase of different units of an underground gas storage (UGS) in the period of gas injection was studied with respect to its hydrochemical composition and characterized microbiologically. The presence of viable aerobic and anaerobic bacteria was revealed in the UGS stratal and associated waters. An important source of microorganisms and biogenic elements in the ecosystem studied is water and various technogenic admixtures contained in trace amounts in the gas entering from the gas main in the period of gas injection into the storage. Owing to this fact, the bacterial functional diversity, number, and activity are maximal in the system of gas treatment and purification and considerably lower in the observation well zone. At the terminal stages, the anaerobic transformation of organic matter in the UGS aqueous media occurs via sulfate reduction and methanogenesis; exceptionally high rates of these processes (up to 4.9 x 10(5) ng S(2-)l(-1) day(-1) and 2.8 x 10(6) nl CH4 l(-1) day(-1), respectively) were recorded for above-ground technological equipment.

[The properties of hydrocarbon-oxidizing bacteria isolated from the oilfields of Tatarstan, Western Siberia, and Vietnam].

Eleven strains of hydrocarbon-oxidizing bacteria, isolated from oilfields, representing the genera Rhodococcus, Gordonia, Dietzia, and Pseudomonas, were characterized as mesophiles and neutrophiles. Rhodococci were halotolerant microorganisms growing in a media containing up to 15% NaCl. All the strains oxidized n-alkanes of crude oil. An influence of the cultivation temperatures (28 or 45 degrees C) and organic supplements on the degradation of C12-C30 n-alkanes in oxidized oil by two bacterial strains of the genus Pseudomonas was shown. The introduction of acetate, propionate, butyrate, ethanol, and sucrose led mainly to the decreased oxidation of petroleum paraffins. At certain cultivation temperatures, the addition of volatile fatty acid salts increased the content of individual n-alkanes in oxidized vs. crude oil.

[Utilization of H2O2 as the oxygen source by bacteria of the genera Pseudomonas and Rhodococcus]. / Ispol'zovanie H2O2 v kachestve istochnika kisloroda bakteriiami rodov Pseudomonas i Rhodococcus.

The growth of bacteria of the genera Pseudomonas and Rhodococcus in the presence of hydrogen peroxide as the sole source of oxygen was studied. The toxic effect of H2O2 in the concentration range of 100-200 microg/ml was shown to extend the lag phase by 2 to 3 days. Apart from the peroxide toxicity, the bacterial growth was inhibited by the toxic effect of dissolved oxygen in concentrations over 100 microg O2/ml; in the presence of a liquid hydrocarbon phase, this effect was alleviated. Under decreased partial pressure of oxygen in the presence of hydrocarbons (12-15 vol %), the culture growth was initiated at high initial concentrations of H2O2 (300 microg/ml). When hydrogen peroxide concentrations exceeded 320 microg/ml, no growth occurred, no matter how much hydrocarbon was added.

[Dynamics of microbial processes in the stratal waters of the Romashkinskoe oil field]. / Dinamika mikrobnykh protsessov v plastovykh vodakh Romashkinskogo neftianogo mestorozhdeniia.

Dynamics of the microbial processes developing in parallel with the exploitation of the Romashkinskoe oil field (Tatarstan) was studied in two areas differing in the degree of stratal water freshening. Flooding the strata in conjunction with purposeful measures on stratal microflora activation was shown to increase the microbial population density and activate both methanogenesis and sulfate-reduction; the latter process was limited by the low sulfate concentration. Development of anaerobic processes correlated with changes in acetate concentration in the stratal water. High mineralization (over 200 g/l) inhibited the stratal water microflora even if other conditions were favorable. Isotopic analysis of the carbonate carbon showed that the bicarbonate concentration increased in the stratal water due to microbial degradation of oil hydrocarbons and further participation of the biogenic carbon dioxide in dissolution of the carbonate cement of the oil-bearing strata. In strongly desalinated stratal water, the proportion of the newly formed bicarbonate was as high as 80%.

[Halophilic archaebacteria from the Kalamkass oilfield]. / Galfil'nye arkhebakterii neftianogo mestorozhdeniia Kalamkass.

Two strains of halophilic archebacteria, growing in the range from 10 to 25% NaCl, were obtained from the brines of the Kalamkass (Mangyshlak) oilfield. Both strains are extremely halophilic archaebacteria according to their total phenotypic properties. Strain M-11 was identified as Haloferax mediterranei on the basis of the composition of polar lipids and DNA-DNA homology. The composition of polar lipids and 16S rRNA sequences of M-18 strain permitted to include it in Haloferax genus. This strain differs from the affirmed species of Haloferax genus--H. volcanii and H. mediterranei. However, the additional investigations are necessary for its relation to new species.