Department of Isotope Biogeochemistry, Helmholtz-Centre for Environmental Research UFZ , Permoserstraße 15, 04318 Leipzig, Germany.
Environ Sci Technol. 2014 Aug 19;48(16):9094-102. doi: 10.1021/es404808r. Epub 2014 Jul 21.
The microbial oxidation of sulfide is a key reaction of the microbial sulfur cycle, recycling sulfur in its most reduced valence state back to more oxidized forms usable as electron acceptors. Under anoxic conditions, nitrate is a preferential electron acceptor for this process. Two enzymatic pathways have been proposed for sulfide oxidation under nitrate reducing conditions, the sulfide:quinone oxidoreductase (SQR) pathway and the Sox (sulfur oxidation) system. In experiments with the model strains Thiobacillus denitrificans and Sulfurimonas denitrificans, both pathways resulted in a similar small sulfur and oxygen isotope fractionation of -2.4 to -3.6‰ for (34)S and -2.4 to -3.4‰ for (18)O. A similar pattern was detected during the oxidation of sulfide in a column percolated with sulfidic, nitrate amended groundwater. In experiments with (18)O-labeled water, a strong oxygen isotope fractionation was observed for T. denitrificans and S. denitrificans, indicating a preferential incorporation of (18)O-depleted oxygen released as water by nitrate reduction to nitrogen. The study indicates that nitrate-dependent sulfide oxidation might be monitored in the environment by analysis of (18)O-depleted sulfate.
硫化物的微生物氧化是微生物硫循环的关键反应，将硫还原到最还原的价态，再循环到更氧化的形式，作为电子受体使用。在缺氧条件下，硝酸盐是该过程的优先电子受体。在硝酸盐还原条件下，已经提出了两种用于硫化物氧化的酶促途径，即硫化物：醌氧化还原酶（SQR）途径和 Sox（硫氧化）系统。在对模型菌株脱氮硫杆菌和硫磺单胞菌的实验中，两种途径都导致类似的小硫和氧同位素分馏，(34)S 的分馏为-2.4 至-3.6‰，(18)O 的分馏为-2.4 至-3.4‰。在用含硫、添加硝酸盐的地下水渗滤柱中氧化硫化物的实验中也检测到了类似的模式。在与 (18)O 标记水的实验中，观察到脱氮硫杆菌和硫磺单胞菌的氧同位素强烈分馏，表明硝酸盐还原产生的水释放的 (18)O 贫氧优先被掺入到氮气中。该研究表明，通过分析 (18)O 贫化的硫酸盐，可能在环境中监测硝酸盐依赖的硫化物氧化。
