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

1978 ◽  
Vol 24 (6) ◽  
pp. 716-724 ◽  
Author(s):  
E. J. Laishley ◽  
H. R. Krouse
Keyword(s):  
Amino Acids ◽  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Sulfite Reductase ◽  
Clostridium Pasteurianum ◽  
Sulfur Amino Acids ◽  
Stable Isotope Fractionation ◽  
Sulfur Isotope Fractionation ◽  
Sulfide Production ◽  
Logarithmic Growth

In addition to an assimilatory sulfite reductase, studies of cultures of Clostridium pasteurianum supplemented with methionine, cysteine, and 35SO42− provide evidence for another reductase which is induced by SO32−. This inducible reductase appears to be dissimilatory 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− + 10 mM cysteine, derepression of the inducible reductase occurred along with increased sulfide production. The presence of 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 δ34S 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.

Stable isotope fractionation by Clostridium pasteurianum. 5. Effect of SeO42− on the physiology and associated sulfur isotope fractionation during SO32− and SO42− reductions

1982 ◽  
Vol 28 (3) ◽  
pp. 325-333 ◽  
Author(s):  
G. I. Harrison ◽  
E. J. Laishley ◽  
H. R. Krouse
Keyword(s):  
Stationary Phase ◽  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Reductase Activity ◽  
Clostridium Pasteurianum ◽  
Elemental Selenium ◽  
Whole Cells ◽  
Stable Isotope Fractionation ◽  
Sulfur Isotope Fractionation ◽  
Inverse Isotope Effect

The addition of 1 mM SeO42− significantly affected the physiology and metabolism of Clostridium pasteurianum growing on SO42− in the following ways: (1) the generation time was increased, essentially producing a biphasic growth curve, (2) cells became elongated and chains formed, (3) no H2S was liberated during the stationary phase, (4) assimilatory SO32− reductase activity was decreased, (5) ferredoxin levels decreased by a factor of 4. The effects of 1 mM SeO42− on Clostridium pasteurianum growing on SO32− were comparatively minor.H2S evolution in the stationary phase decreased by a factor of 2 and the δ34S maximum in the inverse isotope effect pattern occurred at a slightly lower percent H2S evolution. The deleterious effects of SeO42− addition were less pronounced than those associated with SeO32− addition. SeO32− but not SeO42− was reduced to elemental selenium by both whole cells and crude extracts.

Stable isotope fractionation by Clostridium pasteurianum. 4. Sulfur isotope fractionation during enzymatic S3O62−, S2O32−, and SO32− reductions

1981 ◽  
Vol 27 (8) ◽  
pp. 824-834
Author(s):  
G. I. Harrison ◽  
E. J. Laishley ◽  
H. R. Krouse
Keyword(s):  
Stable Isotope ◽  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Isotope Effects ◽  
Growth Conditions ◽  
Enzyme Concentration ◽  
Clostridium Pasteurianum ◽  
Relative Reduction ◽  
Stable Isotope Fractionation ◽  
Sulfur Isotope Fractionation

Cell-free extracts from Clostridium pasteurianum grown on SO32− utilize H2 to reduce S3O62−, S2O32−, and SO32− to H2S at a much faster rate than extracts from SO42−-grown cells. This further supports the concept of an inducible dissimilatory type SO32− reductive pathway in this organism. 35S dilution experiments further support the concept that S3O62− and S2O32− are pathway intermediates. The inducible SO32− 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 S2O32−, 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.

Thiosulfate formation and associated isotope effects during sulfite reduction by Clostridium pasteurianum

1979 ◽  
Vol 25 (6) ◽  
pp. 719-721 ◽  
Author(s):  
L. A. Chambers ◽  
P. A. Trudinger
Keyword(s):  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Isotope Effects ◽  
Clostridium Pasteurianum ◽  
Stages Of Growth ◽  
Bacterial Cultures ◽  
Sulfur Isotope Fractionation ◽  
Secondary Chemical Reaction ◽  
Secondary Chemical ◽  
Isotopic Effects

During growth of Clostridium pasteurianum on sulfite, approximately half the sulfite was reduced to sulfide and half to thiosulfate. Sulfide was enriched in 32S or 34S at different stages of growth and thiosulfate was enriched in 32S, particularly in the sulfane atom.It is suggested that thiosulfate in these bacterial cultures arose from a secondary chemical reaction. The chemical formation of thiosulfate from sulfide and sulfite was also accompanied by sulfur isotope fractionation. The implications of these results with respect to 'inverse' isotopic effects are discussed.

Stable isotope fractionation by Clostridium pasteurianum. 3. Effect of SeO32– on the physiology and associated sulfur isotope fractionation during SeO32– and SeO42– reductions

1980 ◽  
Vol 26 (8) ◽  
pp. 952-958 ◽  
Author(s):  
G. I. Harrison ◽  
E. J. Laishley ◽  
H. R. Krouse
Keyword(s):  
Isotope Fractionation ◽  
Chemical Mechanism ◽  
Clostridium Pasteurianum ◽  
Whole Cells ◽  
In Vivo Experiments ◽  
Stable Isotope Fractionation ◽  
Sulfur Isotope Fractionation ◽  
Generation Times

Increased [Formula: see text] concentration reduced H2S evolution from [Formula: see text] during whole cell and cell-free extract reductions by Clostridium pasteurianum. H2S production from [Formula: see text] was completely inhibited by [Formula: see text] in stationary phase cells. Generation times increased with greater [Formula: see text] concentration, the increase with 1 mM[Formula: see text] being a factor of 2.5 for 1 mM[Formula: see text], and over 3 for 1 mM[Formula: see text] reductions. In vitro and in vivo experiments with proposed intermediates of the [Formula: see text] reduction pathway show that [Formula: see text] inhibited both the [Formula: see text] to [Formula: see text] and [Formula: see text] to S2− reaction sequences with the latter being more pronounced in growth experiments. Both extracts and whole cells reduced [Formula: see text], to Se0 but Se0 granules were not found in the cell's cytoplasm. The formation of [Formula: see text] by an extracellular chemical mechanism appears not to have occurred in these experiments. Increased [Formula: see text] 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 mimimum values of δ34S. Thus, inhibition by [Formula: see text] limited the conversions of sulfur species without altering the isotopic selectivity of rate-controlling steps in the pathway.

Stable isotope fractionation by Clostridium pasteurianum. 1.34S/32S: inverse isotope effects during SO42− and SO32− reduction

1975 ◽  
Vol 21 (3) ◽  
pp. 235-244 ◽  
Author(s):  
R. G. L. McCready ◽  
E. J. Laishley ◽  
H. R. Krouse
Keyword(s):  
Isotope Fractionation ◽  
Isotope Effects ◽  
Sulfite Reductase ◽  
Clostridium Pasteurianum ◽  
Stages Of Growth ◽  
Dissimilatory Sulfite Reductase ◽  
Stable Isotope Fractionation ◽  
High Concentrations ◽  
Late Stages ◽  
Isotopic Effects

During growth on minimal salts – sucrose media supplemented with various concentrations (10−4–10−2 M) of sodium sulfate, Clostridium pasteurianum grew at a normal rate and only evolved sulfide in late stages of growth on 10−2 M SO42−. The evolved sulfide was slightly enriched in 34S as compared to the medium sulfur. On the other hand, sulfide was evolved during growth on all concentrations of sulfite tested. Large normal and inverse isotopic effects were observed in the evolved sulfide during SO32− reductions. In contrast, the intracellular sulphur showed much smaller fractionations. The complexity of the isotopic patterns suggests that a dissimilatory sulfite reductase system may be induced by high concentrations of sulfite.

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