Thiosulfate oxidation by sulfur-grown <i>Thiobacillus thiooxidans</i> cells, cell-free extracts, and thiosulfate-oxidizing enzyme

Chan, Cheryl; Suzuki, Isamu

doi:10.1139/m94-130

Cited by 12 publications

(3 citation statements)

References 33 publications

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“…Kodama and Mori (1968) showed a strong inhibition of sulfur oxidation by NEM in sulfur-grown T. thiooxidans cells without any inhibition of sulfite oxidation. The NEM-treated cells oxidized thiosulfate to tetrathionate only (Chan and Suzuki 1994). Hazeu et al (1988) showed the inhibition of the oxidation of sulfide, thiosulfate, and tetrathionate by NEM at the level of sulfur in T. ferrooxidans cells grown on tetrathionate.…”

Section: Discussionmentioning

confidence: 92%

“…. Although resting cells of the organism grown on sulfur can oxidize thiosulfate at pH 2.3 (Chan and Suzuki 1994), the acidic pH used for growth on sulfur where thiosulfate is chemically more reactive, the organism cannot grow on thiosulfate at this pH. Growth can be achieved only at a higher pH of 4.5-5.0 (Barton and Shively 1968;Nakamura et al 1990).…”

Section: -mentioning

confidence: 99%

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

Masau¹,

Oh²,

Suzuki³

2001

Can. J. Microbiol.

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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, delta muH+, required either for electron transfer from cytochrome c to b or for sulfite binding.

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Section: Discussionmentioning

confidence: 92%

Section: -mentioning

confidence: 99%

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

Masau¹,

Oh²,

Suzuki³

2001

Can. J. Microbiol.

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“…NEM also inhibited the oxidation of S 2Ϫ at the level of S 0 , as shown by spectrophotometric data and confirmed by analysis of the cell suspensions used in those reactions. NEM reduced the oxidation rates of sulfur compounds in T. caldus more than in other acidophiles (3,19,22). These results suggest that sulfhydryl groups are involved in the oxidation of the reduced sulfur compounds, specifically sulfur.…”

Section: ϫmentioning

confidence: 99%

Reduced sulfur compound oxidation by Thiobacillus caldus

1996

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The oxidation of reduced inorganic sulfur compounds was studied by using resting cells of the moderate thermophile Thiobacillus caldus strain KU. The oxygen consumption rate and total oxygen consumed were determined for the reduced sulfur compounds thiosulfate, tetrathionate, sulfur, sulfide, and sulfite in the absence and in the presence of inhibitors and uncouplers. The uncouplers 2,4-dinitrophenol and carbonyl cyanide m-chlorophenyl-hydrazone had no affect on the oxidation of thiosulfate, suggesting that thiosulfate is metabolized periplasmically. In contrast, the uncouplers completely inhibited the oxidation of tetrathionate, sulfide, sulfur, and sulfite, indicating that these compounds are metabolized in the cytoplasm of T. caldus KU. N-Ethylmaleimide inhibited the oxidation of tetrathionate and thiosulfate at the stage of elemental sulfur, while 2-heptyl-4-hydroxyquinoline-N-oxide stopped the oxidation of thiosulfate, tetrathionate, and elemental sulfur at the stage of sulfite. The following intermediates in the oxidation of the sulfur compounds were found by using uncouplers and inhibitors: thiosulfate was oxidized to tetrathionate, elemental sulfur was formed during the oxidation of tetrathionate and sulfide, and sulfite was found as an intermediate of tetrathionate and sulfur metabolism. On the basis of these data we propose a model for the metabolism of the reduced inorganic sulfur compounds by T. caldus KU.Thiobacillus caldus KU (5) is a moderately thermophilic acidophile found in environments such as coal spoil heaps (17), where the oxidative dissolution of sulfide minerals occurs. This bacterium obtains its carbon by reductive fixation of atmospheric CO 2 . T. caldus is capable of oxidizing a wide range of reduced sulfur compounds, but it is incapable of oxidizing ferrous iron or pyrite. One of the products of the oxidation of reduced sulfur compounds is H 2 SO 4 , and this bacterium is able to live in acidic environments, down to pH 1.One biotechnological application of acidophilic bacteria is the biooxidation of refractory sulfidic ores for the enhanced recovery of gold (13,14). The gold is often associated with the iron sulfides pyrite (FeS 2 ) and arsenopyrite (FeAsS) as fine particles trapped within the mineral matrix. During the biooxidation process, the iron sulfides are oxidized to soluble ferric iron and sulfate, liberating the gold particles. It has been found that T. caldus is the primary sulfur oxidizer enriched from pilot scale bioleaching reactors operating at temperatures above 40ЊC (4). In a different pilot scale study of reactors operating between 45 and 50ЊC, T. caldus makes up approximately 10% of the total bacterial population (1).Recent studies regarding the sulfur metabolism by bacteria of the genus Thiobacillus have focused on two acidophilic mesophilic species, T. ferrooxidans and T. acidophilus, and a moderately thermophilic neutrophile, T. tepidarius. It has been proposed that T. acidophilus is a suitable organism for use as a model of sulfur oxidation for thiobacilli (24)....

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Purification and characterization of a periplasmic thiosulfate dehydrogenase from the obligately autotrophicThiobacillus sp. W5

et al. 1996

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A periplasmic thiosulfate dehydrogenase (EC 1.8.2.2) was purified to homogeneity from the neutrophilic, obligately chemolithoautotrophic Thiobacillus sp. W5. A five-step procedure resulted in an approximately 2,300-fold purification. The purified protein had a molecular mass of 120 +/- 3 kDa, as determined by gel filtration. It is probably a tetramer containing two different subunits with molecular masses of 33 +/- 1 kDa and 27 +/- 0.5 kDa, as determined by SDS-PAGE. UV/visible spectroscopy revealed that the enzyme contained haem c; haem staining showed that both subunits contained haem c. A haem c content of 4 mol per mol of enzyme was calculated using the pyridine haemochrome test. The pH optimum of the enzyme was 5.5. At pH 7.5, the Km and Vmax were 120 +/- 10 microM and 1,160 +/- 30 U mg-1, respectively. The absence of 2-heptyl-4-hydroquinoline-N-oxide (HQNO) inhibition for the oxidation of thiosulfate by whole cells suggested that the electrons enter the respiratory chain at the level of cytochrome c. Comparison with thiosulfate dehydrogenases from other Thiobacillus species showed that the enzyme was structurally similar to the thiosulfate dehydrogenase of the acidophilic, facultatively chemolithoautotrophic Thiobacillus acidophilus, but not to the thiosulfate dehydrogenases published for the obligately chemolithoautotrophic Thiobacillus tepidarius and Thiobacillus thioparus.

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Thiosulfate oxidation by sulfur-grown Thiobacillus thiooxidans cells, cell-free extracts, and thiosulfate-oxidizing enzyme

Cited by 12 publications

References 33 publications

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

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

Reduced sulfur compound oxidation by Thiobacillus caldus

Purification and characterization of a periplasmic thiosulfate dehydrogenase from the obligately autotrophicThiobacillus sp. W5

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