School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, Hubei, China.
Environ Sci Technol. 2023 Dec 5;57(48):19817-19826. doi: 10.1021/acs.est.3c06490. Epub 2023 Nov 16.
Iodate (IO) can be abiotically reduced by Fe(II) or biotically reduced by the dissimilatory Fe(III)-reducing bacterium (MR-1) via its DmsEFAB and MtrCAB. However, the intermediates and stoichiometry between the Fe(II) and IO reaction and the relative contribution of abiotic and biotic IO reduction by biogenic Fe(II) and MR-1 in the presence of Fe(III) remain unclear. In this study, we found that abiotic reduction of IO by Fe(II) produced intermediates HIO and I at a ratio of 1:2, followed by HIO disproportionation to I and IO. Comparative analyses of IO reduction by MR-1 wild type (WT), MR-1 mutants deficient in DmsEFAB or MtrCAB, and sp. ANA-3 in the presence of Fe(III)-citrate, Fe(III) oxides, or clay minerals showed that abiotic IO reduction by biogenic Fe(II) predominated under iron-rich conditions, while biotic IO reduction by DmsEFAB played a more dominant role under iron-poor conditions. Compared to that in the presence of Fe(III)-citrate, MR-1 WT reduced more IO in the presence of Fe(III) oxides and clay minerals. The observed abiotic and biotic IO reduction by MR-1 under Fe-rich and Fe-limited conditions suggests that Fe(III)-reducing bacteria could contribute to the transformation of iodine species and I enrichment in natural iodine-rich environments.
碘酸盐 (IO) 可以通过 Fe(II) 非生物还原或异化铁还原菌 (MR-1) 通过其 DmsEFAB 和 MtrCAB 生物还原。然而，Fe(II)与 IO 反应的中间体和化学计量比以及生物源 Fe(II)和 MR-1 在 Fe(III)存在下对 IO 还原的非生物和生物还原的相对贡献仍不清楚。在这项研究中，我们发现 Fe(II)对 IO 的非生物还原产生了中间体 HIO 和 I，其比例为 1:2，随后 HIO 歧化生成 I 和 IO。MR-1 野生型 (WT)、DmsEFAB 或 MtrCAB 缺陷突变体以及 sp. ANA-3 在 Fe(III)-柠檬酸盐、Fe(III)氧化物或粘土矿物存在下还原 IO 的比较分析表明，在富铁条件下，生物源 Fe(II)主导非生物 IO 还原，而在贫铁条件下，DmsEFAB 的生物 IO 还原作用更为突出。与在 Fe(III)-柠檬酸盐存在的情况下相比，MR-1 WT 在 Fe(III)氧化物和粘土矿物存在的情况下还原了更多的 IO。MR-1 在富铁和缺铁条件下对 IO 的非生物和生物还原表明，Fe(III)还原菌可能有助于碘物种的转化和富碘环境中 I 的富集。
