Tetrathionate and Elemental Sulfur Shape the Isotope Composition of Sulfate in Acid Mine Drainage.
Tetrathionate and Elemental Sulfur Shape the Isotope Composition of Sulfate in Acid Mine Drainage.
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DOI：
10.3389/fmicb.2017.01564
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发表时间：
2017
影响因子：
5.2
通讯作者：
Turchyn AV
中科院分区：
文献类型：
--
作者：
Balci N;Brunner B;Turchyn AV
处于中间价态的硫化合物，例如元素硫、硫代硫酸盐和连四硫酸盐，是地球化学硫循环中的重要参与者。然而，关键的理解涉及混合价态硫物种的氧化途径仍然缺失。在这里，我们报告了在酸性条件下细菌培养物中连四硫酸盐（S4O62−）和元素硫（S°）氧化为硫酸盐过程中的硫和氧同位素分馏效应。嗜酸氧化硫硫杆菌氧化连四硫酸盐产生硫代硫酸盐、元素硫和硫酸盐。在实验中，细菌消耗的连四硫酸盐中高达34%不能以硫酸盐或其他中间价态硫物种的形式存在。连四硫酸盐的氧化产生硫酸盐，最初富含+7.9‰的34S（ε34SSO4−S4O6），然后在实验期间下降到+1.4‰，在一个月的培养后，平均ε34SSO4−S4O6为+3.5 ± 0.2‰。我们将这种显著的硫同位素分馏归因于连四硫酸盐分解过程中发生的酶促分解反应，以及连四硫酸盐向硫酸盐的不完全转化。连四硫酸盐氧化实验中硫酸盐的氧同位素组成（δ18OSO4）表明，生成的硫酸盐中62%的氧来自水。剩余的38%的氧来自所提供的连四硫酸盐，或者来自溶解的大气氧（O2）。在元素硫的氧化过程中，产物硫酸盐中的34 S相对于元素硫在−1.8至0‰之间贫化，平均ε34SSO4−S0为−0.9 ± 0.2‰，硫酸盐中的所有氧原子都来自水，平均正常氧同位素分馏（ε18OSO4−H2O）为−4.4‰。在δ18OSO4和硫酸盐的硫同位素组成（δ34SSO4）、酸的产生和由两种不同底物氧化产生的混合价态硫物质中观察到的差异表明了对硫底物可用性的代谢灵活性。我们的研究结果表明，微生物处理的混合价态硫物种在酸性环境中产生显着的硫同位素分馏和氧化的混合价态硫物种可能会产生硫酸盐的特征硫和氧同位素签名。元素硫和连四硫酸盐不仅是在硫氧化途径中起核心作用的中间价态硫化合物，而且是形成这些同位素模式的关键因素。
Sulfur compounds in intermediate valence states, for example elemental sulfur, thiosulfate, and tetrathionate, are important players in the biogeochemical sulfur cycle. However, key understanding about the pathways of oxidation involving mixed-valance state sulfur species is still missing. Here we report the sulfur and oxygen isotope fractionation effects during the oxidation of tetrathionate (S4O62−) and elemental sulfur (S°) to sulfate in bacterial cultures in acidic conditions. Oxidation of tetrathionate by Acidithiobacillus thiooxidans produced thiosulfate, elemental sulfur and sulfate. Up to 34% of the tetrathionate consumed by the bacteria could not be accounted for in sulfate or other intermediate-valence state sulfur species over the experiments. The oxidation of tetrathionate yielded sulfate that was initially enriched in 34S (ε34SSO4−S4O6) by +7.9‰, followed by a decrease to +1.4‰ over the experiment duration, with an average ε34SSO4−S4O6 of +3.5 ± 0.2‰ after a month of incubation. We attribute this significant sulfur isotope fractionation to enzymatic disproportionation reactions occurring during tetrathionate decomposition, and to the incomplete transformation of tetrathionate into sulfate. The oxygen isotope composition of sulfate (δ18OSO4) from the tetrathionate oxidation experiments indicate that 62% of the oxygen in the formed sulfate was derived from water. The remaining 38% of the oxygen was either inherited from the supplied tetrathionate, or supplied from dissolved atmospheric oxygen (O2). During the oxidation of elemental sulfur, the product sulfate became depleted in 34S between −1.8 and 0‰ relative to the elemental sulfur with an average for ε34SSO4−S0 of −0.9 ± 0.2‰ and all the oxygen atoms in the sulfate derived from water with an average normal oxygen isotope fractionation (ε18OSO4−H2O) of −4.4‰. The differences observed in δ18OSO4 and the sulfur isotope composition of sulfate (δ34SSO4), acid production, and mixed valence state sulfur species generated by the oxidation of the two different substrates suggests a metabolic flexibility in response to sulfur substrate availability. Our results demonstrate that microbial processing of mixed-valence-state sulfur species generates a significant sulfur isotope fractionation in acidic environments and oxidation of mixed-valence state sulfur species may produce sulfate with characteristic sulfur and oxygen isotope signatures. Elemental sulfur and tetrathionate are not only intermediate-valence state sulfur compounds that play a central role in sulfur oxidation pathways, but also key factors in shaping these isotope patterns.
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影响因子：
5
作者：
Balci, Nurgul;Shanks, Wayne C., III;Mandernack, Kevin W.
通讯作者：
Mandernack, Kevin W.
影响因子：
3.9
作者：
FRY, B;RUF, W;HAYES, JM
通讯作者：
HAYES, JM
影响因子：
3.2
作者：
Hallberg, KB;Dopson, M;Lindstrom, EB
通讯作者：
Lindstrom, EB
影响因子：
2.8
作者：
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通讯作者：
Balci, Nurgul Celik
影响因子：
5
作者：
CHIBA, H;SAKAI, H
通讯作者：
SAKAI, H