Oxidation of inorganic sulfur compounds: Chemical and enzymatic reactions

Microbial oxidation of inorganic sulfur compounds is governed by both chemical and enzymatic reactions. It is therefore essential to understand reactions possible in chemistry when we consider enzymatic reactions. Various oxidation states of sulfur atoms in inorganic sulfur compounds and chemical oxidation reactions as well as nucleophilic cleavage of sulfur-sulfur bonds are discussed. The scheme of enzymatic oxidation of sulfur compounds with S2-→> S0→> SO32-→> SO42-as the main oxidation pathway is discussed with thiosulfate and polythionates leading into the main pathway for complete oxidation to sulfate. Enzymatic reactions are related to chemical reactions and the use of inhibitors for S0→> SO32-and SO32-→> SO42-is discussed for analyzing and establishing reaction stoichiometries. The proposed pathway is supported by a variety of evidence in many different microorganisms including some genetic evidence if the oxidation steps include all the systems irrespective of oxidizing agents (O2, Fe3+, cytochromes etc.).Key words: sulfur, oxidation, chemical, enzymatic, reactions.

Download Full-text

An Overview of the Biochemical and Molecular Aspects of Microbial Oxidation of Inorganic Sulfur Compounds

CLEAN - Soil Air Water ◽

10.1002/clen.200700213 ◽

2008 ◽

Vol 36 (10-11) ◽

pp. 823-829 ◽

Cited By ~ 9

Author(s):

Bidyut R. Mohapatra ◽

W. Douglas Gould ◽

Orlando Dinardo ◽

David W. Koren

Keyword(s):

Sulfur Compounds ◽

Microbial Oxidation ◽

Inorganic Sulfur ◽

Molecular Aspects

Download Full-text

OXIDATION OF INORGANIC SULFUR COMPOUNDS BY WASHED CELL SUSPENSIONS OF THIOBACILLUS FERROOXIDANS

Canadian Journal of Microbiology ◽

10.1139/m66-129 ◽

1966 ◽

Vol 12 (5) ◽

pp. 957-964 ◽

Cited By ~ 34

Author(s):

J. Landesman ◽

D. W. Duncan ◽

C. C. Walden

Keyword(s):

Organic Compounds ◽

Elemental Sulfur ◽

Thiobacillus Ferrooxidans ◽

Sulfur Oxidation ◽

Sulfur Compounds ◽

Maximum Temperature ◽

Washed Cell ◽

Inorganic Sulfur ◽

Respiration Rates ◽

Growth Adaptation

Oxidation of various inorganic sulfur compounds by Thiobacillus ferrooxidans was studied, and conditions necessary for maximum respiration rates were established. Optimum oxidation of elemental sulfur occurred at pH 5.0 and gave a Qo2(N) of 726; oxidation of thiosulfate gave a maximum Qo2(N) of 514 at pH 4.0; tetra- and tri-thionate, when oxidized at pH 6.0, gave a maximum Qo2(N) of 103 and 113, respectively. Polythionates accumulated during thiosulfate oxidation, but did not during oxidation of elemental sulfur. Metallic sulfide minerals were oxidized optimally as follows: chalcopyrite, pH 2.0, maximum Qo2(N) 3200; bornite, pH 3.0, maximum Qo2(N) 450; pyrite, pH 2.0, maximum Qo2(N) 1600. Maximum temperature for oxidation of all inorganic sulfur compounds tested was 40 C.The effect of a variety of organic compounds on sulfur oxidation is presented.T. ferrooxidans requires growth adaptation on iron for maximum respiration on that substrate; however, sulfur oxidation is not inducible. Iron and sulfur can be oxidized simultaneously, giving a rate equal to the sum of the maximum rates of oxidation of the two substrates individually.

Download Full-text

Probing enzyme-mediated oxidation reactions in crystallo

Pure and Applied Chemistry ◽

10.1351/pac-con-11-08-10 ◽

2011 ◽

Vol 83 (12) ◽

pp. 2199-2212 ◽

Cited By ~ 1

Author(s):

Chengqi Yi

Keyword(s):

Single Crystals ◽

Critical Review ◽

Focal Point ◽

Enzymatic Oxidation ◽

Enzymatic Reactions ◽

Reaction Intermediates ◽

Oxidation Reactions ◽

Enzymatic Mechanisms ◽

Oxidation Mechanisms ◽

Mediated Oxidation

Reaction intermediates define the chemical steps of transformation from substrates to products, and capture of intermediates along catalytic pathways remains one focal point in the studies of enzymatic mechanisms. Performing enzymatic reactions in protein single crystals has been shown to be very effective in trapping and identifying unstable intermediates. In this critical review, we provide several examples of in crystallo approaches to trap reactive oxidation intermediates, thereby allowing the studies of enzymatic oxidation mechanisms.

Download Full-text

Mechanism of oxidation of inorganic sulfur compounds by thiosulfate-grown Thiobacillus thiooxidans

Canadian Journal of Microbiology ◽

10.1139/w01-015 ◽

2001 ◽

Vol 47 (4) ◽

pp. 348-358 ◽

Cited By ~ 16

Author(s):

Rosemarie Jefferey Y Masau ◽

Jae Key Oh ◽

Isamu Suzuki

Keyword(s):

Sulfur Oxidation ◽

Optimal Growth ◽

Sulfur Compounds ◽

Intact Cells ◽

Thiobacillus Thiooxidans ◽

Inorganic Sulfur ◽

Sulfite Oxidation ◽

Mechanism Of Oxidation ◽

Hydroxy Quinoline ◽

In Cells

Thiobacillus thiooxidans was grown at pH 5 on thiosulfate as an energy source, and the mechanism of oxidation of inorganic sulfur compounds was studied by the effect of inhibitors, stoichiometries of oxygen consumption and sulfur, sulfite, or tetrathionate accumulation, and cytochrome reduction by substrates. Both intact cells and cell-free extracts were used in the study. The results are consistent with the pathway with sulfur and sulfite as the key intermediates. Thiosulfate was oxidized after cleavage to sulfur and sulfite as intermediates at pH 5, the optimal growth pH on thiosulfate, but after initial condensation to tetrathionate at pH 2.3 where the organism failed to grow. N-Ethylmaleimide (NEM) inhibited sulfur oxidation directly and the oxidation of thiosulfate or tetrathionate indirectly. It did not inhibit the sulfite oxidation by cells, but inhibited any reduction of cell cytochromes by sulfur, thiosulfate, tetrathionate, and sulfite. NEM probably binds sulfhydryl groups, which are possibly essential in supplying electrons to initiate sulfur oxidation. 2-Heptyl-4-hydroxy-quinoline N-oxide (HQNO) inhibited the oxidation of sulfite directly and that of sulfur, thiosulfate, and tetrathionate indirectly. Uncouplers, carbonyl cyanide-m-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNP), inhibited sulfite oxidation by cells, but not the oxidation by extracts, while HQNO inhibited both. It is proposed that HQNO inhibits the oxidation of sulfite at the cytochrome b site both in cells and extracts, but uncouplers inhibit the oxidation in cells only by collapsing the energized state of cells, ΔµH+, required either for electron transfer from cytochrome c to b or for sulfite binding.Key words: Thiobacillus thiooxidans, thiosulfate, oxidation, sulfite.

Download Full-text

A novel bacterial sulfur oxidation pathway provides a new link between the cycles of organic and inorganic sulfur compounds

The ISME Journal ◽

10.1038/s41396-018-0209-7 ◽

2018 ◽

Vol 12 (10) ◽

pp. 2479-2491 ◽

Cited By ~ 32

Author(s):

Tobias Koch ◽

Christiane Dahl

Keyword(s):

Sulfur Oxidation ◽

Sulfur Compounds ◽

Inorganic Sulfur ◽

Oxidation Pathway

Download Full-text

Chemical Modification of Polysaccharides

ISRN Organic Chemistry ◽

10.1155/2013/417672 ◽

2013 ◽

Vol 2013 ◽

pp. 1-27 ◽

Cited By ~ 92

Author(s):

Ian Cumpstey

Keyword(s):

Chemical Modification ◽

Carboxylic Acids ◽

Uronic Acid ◽

Chemical Oxidation ◽

Enzymatic Oxidation ◽

Enzymatic Reactions ◽

Primary Alcohols ◽

Chemical Methods ◽

Properties Of Materials ◽

Polysaccharide Derivatives

This review covers methods for modifying the structures of polysaccharides. The introduction of hydrophobic, acidic, basic, or other functionality into polysaccharide structures can alter the properties of materials based on these substances. The development of chemical methods to achieve this aim is an ongoing area of research that is expected to become more important as the emphasis on using renewable starting materials and sustainable processes increases in the future. The methods covered in this review include ester and ether formation using saccharide oxygen nucleophiles, including enzymatic reactions and aspects of regioselectivity; the introduction of heteroatomic nucleophiles into polysaccharide chains; the oxidation of polysaccharides, including oxidative glycol cleavage, chemical oxidation of primary alcohols to carboxylic acids, and enzymatic oxidation of primary alcohols to aldehydes; reactions of uronic-acid-based polysaccharides; nucleophilic reactions of the amines of chitosan; and the formation of unsaturated polysaccharide derivatives.

Download Full-text

The Lead Dioxide Anode. II. The Kinetics and Participation of the Lead Dioxide Electrode in Electrochemical Oxidation Reactions in Sulfuric Acid

Australian Journal of Chemistry ◽

10.1071/ch9891527 ◽

1989 ◽

Vol 42 (9) ◽

pp. 1527 ◽

Cited By ~ 3

Author(s):

TH Randle ◽

AT Kuhn

Keyword(s):

Sulfuric Acid ◽

Electrochemical Oxidation ◽

Maximum Rate ◽

Lead Dioxide ◽

Chemical Oxidation ◽

Oxidation Reactions ◽

Electrochemical Regeneration ◽

Electrode Surfaces ◽

Lead Dioxide Electrode ◽

Lead Dioxide Anode

Lead dioxide is a strong oxidizer in sulfuric acid, consequently electrochemical oxidation of solution species at a lead dioxide anode may occur by a two-step, C-E process (chemical oxidation of solution species by PbO2 followed by electrochemical regeneration of the reduced lead dioxide surface). The maximum rate of each step has been determined in sulfuric acid for specified lead dioxide surfaces and compared with the rates observed for the electrochemical oxidation of cerium(III) and manganese(II) on the same electrode surfaces. While the rate of electrochemical oxidation of a partially reduced PbO2 surface may be sufficient to support the observed rates of CeIII and MnII oxidation at the lead dioxide anode, the rate of chemical reaction between PbO2 and the reducing species is not. Hence it is concluded that the lead dioxide electrode functions as a simple, 'inert' electron-transfer agent during the electrochemical oxidation of CellI and MnII in sulfuric acid. In general, it will most probably be the rate of the chemical step which determines the feasibility or otherwise of the C-E mechanism.

Download Full-text