[Effect of microorganisms and seasonal factors on the isotope composition of organic carbon from Black Sea suspensions]. / Vliianie mikroorganizmov i sezonnykh faktorov na izotopnyi sostav organicheskogo ugleroda vzvesi chernogo moria.

The isotopic composition of particulate organic carbon (POC) from the Black Sea deep-water zone was studied during a Russian-Swiss expedition in May 1998. POC from the upper part of the hydrogen sulfide zone (the C-layer) was found to be considerably enriched with the 12C isotope, as compared to the POC of the oxycline and anaerobic zone. In the C-layer waters, the concurrent presence of dissolved oxygen and hydrogen sulfide and an increased rate of dark CO2 fixation were recorded, suggesting that the change in the POC isotopic composition occurs at the expense of newly formed isotopically light organic matter of the biomass of autotrophic bacteria involved in the sulfur cycle. In the anaerobic waters below the C-layer, the organic matter of the biomass of autotrophs is consumed by the community of heterotrophic microorganisms; this results in weighting of the POC isotopic composition. Analysis of the data obtained and data available in the literature allows an inference to be made about the considerable seasonable variability of the POC delta 13C value, which depends on the ratio of terrigenic and planktonogenic components in the particulate organic matter.

[Daily changes in the carbon isotope composition of CO2 in expired air of persons with various metabolic disorders]. / Sutochnye izmeneniia izotopnogo sostava ugleroda CO2 vydykhaemogo vozdukha u cheloveka pri nekotorykh narusheniiakh metabolizma.

Daily variations of the aspiration CO2 carbon isotope content (CIC) were studied at three metabolic states: norm, insulin-dependent diabetes (IDD), and obesity. The groups of subjects were studied in a clinic during 24 hours. Analysis of the delta 13C daily curves of the exhaled air CO2 allowed us to find the link between variations of CIC with daily rhythms in the organism and with metabolic shifts at IDD and obesity. At metabolic norm it is possible two phases on the daily curve, corresponding to daytime and nighttime metabolism types with hormonally regulated transition between them. The daytime phase of the curve consists of altering maxima and minima, linked to periodicity in feeding and movement activity. The nighttime phase is characterized by continuous enrichment of CO2 by 12C. At IDD in insulin therapy conditions the most prominent difference from norm and obesity is the stable CIC at nighttime. At daytime during weakening of the exogenous insulin action there appear horizontal regions on the delta 13C CO2 curves, similar to the nighttime behaviour. At obesity the daily curves are close to the normal ones, but they are more smooth and impoverished in 13C. No clear transition between the daytime and nighttime metabolism types can be observed. At obesity and IDD the character of the daily curves can be observed.

[Role of phospholipids in the fractionation of stable sulfur isotopes during oxidation by Thiobacillus ferrooxidans]. / O roli fosfolipidov v fraktsionirovanii stabil'nykh izotopov sery pri ee okislenii Thiobacillus ferrooxidans.

The action of Thiobacillus ferrooxidans on elementary suhur was shown to be a step-wise process connected with the formation of its colloidal forms having a different isotope composition. Certain sulfur forms are in complex with phospholipids. Both exogenous and endogenous phospholipids are involved in the dissolving of sulfur and in the fractionation of its isotopes. Exogenous phospholipids are more active. The authors discuss the role of phospholipids in the solution of sulfur and in its transport into the cell in the course of oxidation by T. ferrooxidans.

[Fractionation of stable isotopes of sulfur during its oxidation by Thiobacillus ferrooxidans]. / Fraktsionirovanie stabil'nykh izotopov sery pri ee okislenii Thiobacillus ferrooxidans.

The fractionation of sulfur isotopes was studied in the process of sulfur oxidation by Thiobacillus ferrooxidans. The isotope effect was observed at all stages of the bacterial growth during sulfur oxidation; as a result, residual sulfur became heavier whereas the fraction of colloidal sulfur and the fraction of sulfates became lighter. The isotope differences between the residual sulfur and the sulfates were greatest at the end of the lag phase (delta 34S = 0.38%) and the beginning of the stationary phase of the cultural growth (delta 34S = 0.34%). As was shown in model experiments, the phospholipids lecithin and cephalin can dissolve sulfur and form products enriched in 32S(delta 34S = -0.51 -1.60%). The mechanism of oxidation of elementary sulfur by Thiobacillus ferrooxidans is discussed.

[Nitrogen transformation as a result of Pseudomonas denitrificans denitrification]. / Prevrashchenie azota v rezul'tate denitrifikatsii Pseudomonas denitrificans.

The energy process of nitrate reduction was studied in the typical soil denitrifying cultures of Pseudomonas denitrificans by mass spectrometry. These microorganisms differed in certain characteristics of the process from the cultures of sporogenic soil denitrifying bacteria belonging to the Bacillus genus. The rate of denitrification by Ps. denitrificans was very high; as the result, losses of 15N from the medium exceeded 80--90%. Ammonia was not produced as the final product of nitrate reduction in the course of denitrification. Apparently, hydroxylamine, hyponitrite or an organic intermediate product of nitrate reduction is produced in the process of its assimilation by the cultures.

[Oxidation of nitrous oxide during decomposition of hydrogen peroxide by catalase]. / Okislenie zakisi azota pri razlozhenii perekisi vodorada katalazoi.

Possible involvement of the catalase mechanism in the elimination of nitrous oxide was studied in model experiments. The concentration of N2O in the gaseous phase was found to decrease due to the decomposition of hydrogen peroxide by catalase. The concentration of NO increased accompanying the removal of N2O from the gaseous phase in the pressure of H2O2 and catalase. Though the observed effect is slight, the oxidation of nitrous oxide during the decomposition of H2O2 by catalase might be one of the mechanisms for biological elimination of N2O under the oxidating conditions.

[Nonsymbiotic nitrogen fixation in the podzolic soils of the Kola Peninsula]. / Nesimbioticheskaia fiksatsiia azota v podzolistykh pochvakh Kol'skogo poluostrova.

Non-symbiotic nitrogen fixation was studied in virgin and cultivated podzol soils of the Kola Peninsula by the acetylene and isotope techniques. The activity of nitrogen fixation varied sharply in cultivated soils due to degradation of plant residues and the action of plant root secretion. No significant changes were observed in the activity of nitrogen fixation within the vegetative period in virgin soils. Less than 1 kg of nitrogen per hectare was accumulated in soils as a result of its non-symbiotic fixation during the vegetative periods of 1976--1977.

[Use of a mass spectrometric method for studying the oxygen demand of suspensions of resting Bacillus anthracoides spores]. / Primenenie mass-spektrometricheskogo metoda dlia izucheniia potrebleniia kisloroda suspenziiami pokoiashchikhsia spo Bacillus anthracoides.

Oxygen assimilation by the spore suspensions of Bacillus anthracoides under sterile conditions was continuously registered by means of a modified mass-spectrometry technique using an original reaction vessel. The sensitivity of the technique is 2.10(-2) mcl O2 per 1 mg of dry biomass per hour. The technique made it possible to determine the level of endogenous respiration activity in the spore suspensions of Bacillus anthracoides.

[Chemcial aspects of the energy process in nitrate reduction in different representatives of soil microflora]. / Khimizm énergeticheskogo protsessa vosstanovleniia nitrata u razlichnykh predstavitelei pochvennoi mikroflory.

Chemical aspects of dissimilatory nitrate reduction were studied by mass spectrometry in the following soil bacteria: Bacillus filaris, Bacillus polymyxa and Pseudomonas denitrificans. Chemical peculiarity of this process in spore-forming soil bacteria is the simultaneous operation of two energy processes: denitrification and nitrate respiration. The first process is terminated by the formation of molecular nitrogen, the second, by the production of ammonia. The quantitative ratio between these processes demonstrates the advantage of nitrate respiration in the overall energy pathway of nitrate dissimilation. Pseudomonas denitrificans maintains the abilityfor intensive gas production as a result of denitrification upon long storage on artificial media: ca. 34 per cent of the nitrate nitrogen is reduced to gaseous forms of nitrogen.

[Oxygen consumption by suspensions of Bacillus anthracoides spores]. / O potreblenii kisloroda suspenziiami spor Bacillus anthracoides

The respiration rate of spore suspensions of Bacillus anthracoides 96 was assayed by mass spectrometry employing a hermetically sealed reaction vessel constructed for this purpose. The rate of respiration was found to depend on the method of preparing suspensions, the duration of their storage at +4 degrees C, the physiological state of spores, and the action of a disinfectant containing chlorine on them.