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At least 19 recordsLinked to original sources
PubMedDate not supplied

[Fractionation of sulfur isotopes by phototrophic sulfur bacterium Ectothiorhodospira shaposhnikovii].

Two processes of sulphur isotope fractionation have been found in experiments with the sulphur purple bacterium Ectothiorhodospira shaposhnikovii. As a result, a light isotope, 32S, is concentrated in residual hydrogen sulphide, and a heavy isotope, 34S, in elementary suphur which is deposited outside the cell. The sulphate produced is lighter than elementary sulphur. Fractionation of sulphur isotopes is observed in natural conditions and is confined to places of mass growth of photosynthetic sulphur bacteria.

Chemical Fractionation↗
PubMed1981

Stable isotope fractionation by Clostridium pasteurianum. 4. Sulfur isotope fractionation during enzymatic S3O6(2-), S2O3(2-), and SO3(2-) reductions.

Cell-free extracts from Clostridium pasteurianum grown on SO3(2-) utilize H2 to reduce S3O6(2-), S2O3(2-), SO3(2-) to H2S at a much faster rate than extracts from SO4(2-)-grown cells. This further supports the concept of an inducible dissimilatory type SO3(2-) reductive pathway in this organism. 35S dilution experiments further support the concept that S3O6(2-) and S2O3(2-) are pathway intermediates. The inducible SO3(2-) reductase is ferredoxin linked and the kinetics of the reduction and the sulfur isotope fractionation of the product can be altered by altering the growth conditions. The attending sulfur isotope fractionations are similar to those observed during the chemical decomposition of these compounds. In the case of S2O3(2-), 35S labelling experiments verified the conclusions derived from the stable isotope fractionation data concerning the relative reduction rates of the sulfane and sulfonate sulfurs. The reduction rates were also affected by enzyme concentration. The integrity of the whole cell is a necessary requirement for the large inverse isotope effects previously reported.

Clostridium↗
PubMed1976

The use of stable sulfur isotope labelling to elucidate sulfur metabolism by Clostridium pasteurianum.

An unique isotope labelling experiment was conducted whereby mixtures of sulfate and sulfite of different isotopic compositions were metabolized by Clostridium pasteurianum. The results showed during reduction of 1 mM SO3= plus 1 mM SO4=, essentially all evolved H2S arose from the sulfite whereas in the case of cellular sulfur, 85% was derived from sulfite and the remainder from sulfate.

Clostridium↗
PubMed1980

Are sulfur isotope ratios sufficient to determine the antiquity of sulfate reduction?

Sulfur isotope fractionation values have been measured in sedimentary sulfides of varying ages, The 'Antiquity and evolutionary status of bacterial sulfate reduction...' has been inferred from these measurements by Schidlowski (1979). However, under experimental conditions, the isotope values vary widely due to inadequately controlled variables. Thus the direct extrapolation of sulfur isotope fractionation values measured in the laboratory to those measured in sedimentary rocks is unwarranted. New sulfur transforming microbes have been described and recent measurements indicate that inorganic processes affect sulfur isotope fractionation values. This information is summarized here; at present sulfur isotope fractionation values are insufficient to determine the antiquity of sulfate reduction.

Desulfovibrio↗
PubMed1979

Antiquity and evolutionary status of bacterial sulfate reduction: sulfur isotope evidence.

The presently available sedimentary sulfur isotope record for the Precambrian seems to allow the following conclusions: (1) In the Early Archaean, sedimentary delta 34S patterns attributable to bacteriogenic sulfate reduction are generally absent. In particular, the delta 34S spread observed in the Isua banded iron formation (3.7 x 10(9) yr) is extremely narrow and coincides completely with the respective spreads yielded by contemporaneous rocks of assumed mantle derivation. Incipient minor differentiation of the isotope pattersn notably of Archaean sulfates may be accounted for by photosynthetic sulfur bacteria rather than by sulfate reducers. (2) Isotopic evidence of dissimilatory sulfate reduction is first observed in the upper Archaean of the Aldan Shield, Siberia (approximately 3.0 x 10(9) yr) and in the Michipicoten and Woman River banded iron formations of Canada (2.75 x 10(9) yr). This narrows down the possible time of appearance of sulfate respirers to the interval 2.8--3.1 x 10(9) yr. (3) Various lines of evidence indicate that photosynthesis is older than sulfate respiration, the SO4(2-) Utilized by the first sulfate reducers deriving most probably from oxidation of reduced sulfur compounds by photosynthetic sulfur bacteria. Sulfate respiration must, in turn, have antedated oxygen respiration as O2-respiring multicellular eucaryotes appear late in the Precambrian. (4) With the bulk of sulfate in the Archaean oceans probably produced by photosynthetic sulfur bacteria, the accumulation of SO4(2-) in the ancient seas must have preceded the buildup of appreciable steady state levels of free oxygen. Hence, the occurrence of sulfate evaporites in Archaean sediments does not necessarily provide testimony of oxidation weathering on the ancient continents and, consequently, of the existence of an atmospheric oxygen reservoir.

Bacteria↗
PubMed1978

Stable isotope fractionation by Clostridium pasteurianum. 2. Regulation of sulfite reductases by sulfur amino acids and their influence on sulfur isotope fractionation during SO32- and SO42- reduction.

In addition to an assimilatory sulfite reductase, studies of cultures of Clostridium pasteurianum supplemented with methionine, cysteine, and 35SO42- provides evidence for another reductase which is induced by SO32-. This inducible reductase appears to be dissimaltory because of the copious sulfide production arising when the cells are grown on SO32-. Cysteine can repress the assimilatory sulfite reductase but does not affect the inducible reductase. During late logarithmic growth on 1 mM SO42- + 10mM cysteine, depression of the inducible reductase occurred along with increased sulfide production. The presence of 1 mM cysteine and (or) 1 mM cysteine and (or) 1 mM methionine does not affect the inverse sulfur isotope effect for evolved H2S. However, 5 and 10 mM cysteine reduce the maximum delta34S value for released H2S from +40 to 10%. A small conversion of cysteine to H2S by C. pasteurianum occurs, but only in the stationary phase.

Cell-Free System↗
PubMed1998

Fractionation of sulfur isotopes during thiosulfate reduction by desulfovibrio desulfuricans

Sulfur isotope fractionation during reduction of thiosulfate was investigated with growing batch cultures of Desulfovibrio desulfuricans CSN (DSM 9104) at 30 degreesC. The sulfide produced was depleted in 34S by 10 per thousand as compared to total thiosulfate sulfur. The depletion was equal to that during sulfate reduction under similar conditions. The two sulfur atoms of the thiosulfate molecule were affected differently by fractionation. Sulfide produced from sulfonate sulfur was depleted by 15.4 per thousand, sulfide produced from sulfane sulfur by 5.0 per thousand.

Journal Article↗
PubMed1984

Sulfur isotope fractionation during SO3(2-) reduction by different clostridial species.

Sulfur isotope composition patterns for sulfide evolved from cultures supplemented with 1 mM Na2SO3, suggested that an inducible dissimilatory type SO3(2-) reduction pathway, as previously found in C. pasteurianum, probably exists in many clostridial species. Data are presented for five additional species which include pathogens and nonpathogens.

Clostridium↗
PubMedDate not supplied

[Role of phospholipids in the fractionation of stable sulfur isotopes during oxidation by 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.

Colloids↗
PubMed1980

Sulfur isotope fractionation by Proteus vulgaris and Salmonella heidelberg during the reduction of thiosulfate.

Proteus vulgaris metabolized thiosulfate to H2S. The amount evolved and its sulfur isotope composition identified it solely with sulfane sulfur. In contrast, Salmonella heidelberg sequentially reduced the sulfane sulfur of S2O3(-2) with slight enrichment of the evolved sulfide in 32S and then reduced the sulfonate sulfur of S2O3(-2) with large isotopic selectivities and an inverse isotopic fractionation pattern. The inverse isotope fractionation pattern for the H2S derived from the sulfonate sulfur was almost identical to that observed during the reduction of high concentrations of sulfite by S. heidelberg.

Hydrogen Sulfide↗
PubMed1968

Sulfur isotope fractionation and kinetic studies of sulfite reduction in growing cells of Salmonella heidelberg.

A pulsed feeding technique was used during studies of sulfite reduction by Salmonella heidelberg in order to realize large percentages of SO(3) (=) conversion while simultaneously maintaining a reasonably stable cell population. As a consequence, much data for conventional kinetic and sulfur isotope fractionation computations were obtained in any one experiment. Under the conditions of supplying 150 mug glucose per ml of medium every 6 hr, anaerobiosis, and varying the SO(3) (=) concentration, the following observations were made: 1. Below 0.01% w/v Na(2)SO(3), the reduction strictly followed first order kinetics with respect to SO(3) (=) concentration. At higher concentrations, the rate of SO(3) (=) reduction fell below that predicted by first order kinetics suggesting that a saturation effect was occurring. 2. At lower concentrations, the ratio of the isotopic rate constants k(1)/k(2) was 1.02 whereas at higher SO(3) (=) levels, k(1)/k(2) values of 1.04 were found. These latter effects are much higher than those obtained in the equivalent chemical reduction. On the basis of these observations, a model is considered which features two isotopically dependent steps and an intermediate reservoir which forms at higher SO(3) (=) concentrations. Results of an experiment under aerobic conditions and an experiment wherein the reduction rate was thermally altered, are also presented.

Chemistry Techniques, Analytical↗
PubMed1996

Photopolymerization and Mass-Independent Sulfur Isotope Fractionations in Carbon Disulfide

Irradiation of gaseous carbon disulfide [CS2(g)] at 313 nanometers produces a dark brown aerosol of (CS2)x. Its thermal decomposition products include disulfur (S2), carbon monosulfide (CS), and (CS)x. The photopolymerization process is accompanied by a large mass-independent isotopic fractionation of sulfur (a 5 to 10 per mil sulfur-33 excess and a 61 to 84 per mil sulfur-36 deficit). Excess sulfur-33 has been observed in several classes of meteorites. Photochemical production of (CS2)x may be important in the origin and evolution of cosmochemical environments such as the presolar nebula, meteorites, asteroids, and planetary atmospheres.

Journal Article↗
PubMed1980

Stable isotope fractionation by Clostridium pasteurianum. 3. Effect of SeO32- on the physiology and associated sulfur isotope fractionation during SO32- and SO42- reductions.

Increased SeO32- concentration reduced H2S evolution from SO32- during whole cell and cell-free extract reductions by Clostridium pasteurianum. H2S production from SO42- was completely inhibited by SeO32- in stationary phase cells. Generation times increased with greater SeO32- concentration, the increase with 1 mM SeO32- being a factor of 2.5 for 1 mM SO32-, and over 3 for 1 mM SO42- reductions. In vitro and in vivo experiments with proposed intermediates of the SO32- reduction pathway show that SeO32- inhibited both the S3O62- to S2O32- and S2O32- to S2- reaction sequences with the latter being more pronounced in growth experiments. Both extracts and whole cells reduced SeO32- to Se0 but Se0 granules were not found in the cell's cytoplasm. The formation of S2O32- by an extracellular chemical mechanism appears not to have occurred in these experiments. Increased SeO32- concentration had the effect of compressing the isotopic release pattern for H2S along the H2S production axis and did not significantly alter the maximum and minimum values of delta 34S. Thus, inhibition by SeO32- limited the conversions of sulfur species without altering the isotopic selectivity of rate-controlling steps in the pathway.

Cell-Free System↗
PubMed1979

Sulfur isotope fractionation by Salmonella heidelberg: inverse isotope effects during growth on high concentrations of Na2SO3.

During growth on minimal salts - glucose media supplemented with high concentrations of Na2SO3 (10-3 and 10-2 M), Salmonella heidelberg exhibited cytological and growth responses which indicated increased cellular toxicity with increasing sulfite concentrations. The large quantities of sulfide evolved during growth at both SO32- concentrations were accompanied by large normal and inverse isotope effects. Consistent with earlier findings, this organism was found capable of rapidly metabolizing both the sulfane and sulfonate sulfur of thiosulfate. Therefore, the isotope effects do not appear to be caused by extracellular chemical thiosulfate formation.

Hydrogen Sulfide↗