Yin Naiyi, Chang Xuhui, Xiao Peng, Zhou Yi, Liu Xiaotong, Xiong Shimao, Wang Pengfei, Cai Xiaolin, Sun Guoxin, Cui Yanshan, Hu Zhengyi
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 101408, People's Republic of China; Research Center for Eco-Environment Sciences, Chinese Academy of Sciences, Beijing 100085, People's Republic of China.
Research Center for Eco-Environment Sciences, Chinese Academy of Sciences, Beijing 100085, People's Republic of China.
Environ Int. 2023 Apr;174:107911. doi: 10.1016/j.envint.2023.107911. Epub 2023 Apr 3.
Gut microbiota provides protection against arsenic (As) induced toxicity, and As metabolism is considered an important part of risk assessment associated with soil As exposures. However, little is known about microbial iron(III) reduction and its role in metabolism of soil-bound As in the human gut. Here, we determined the dissolution and transformation of As and Fe from incidental ingestion of contaminated soils as a function of particle size (<250 μm, 100-250 μm, 50-100 μm and < 50 μm). Colon incubation with human gut microbiota yielded a high degree of As reduction and methylation of up to 53.4 and 0.074 μg/(log CFU/mL)/hr, respectively; methylation percentage increased with increasing soil organic matter and decreasing soil pore size. We also found significant microbial Fe(III) reduction and high levels of Fe(II) (48 %-100 % of total soluble Fe) may promote the capacity of As methylation. Although no statistical change in Fe phases was observed with low Fe dissolution and high molar Fe/As ratios, higher As bioaccessibility of colon phase (avg. 29.4 %) was mainly contributed from reductive dissolution of As(V)-bearing Fe(III) (oxy)hydroxides. Our results suggest that As mobility and biotransformation by human gut microbiota (carrying arrA and arsC genes) are strongly controlled by microbial Fe(III) reduction coupled with soil particle size. This will expand our knowledge on oral bioavailability of soil As and health risks from exposure to contaminated soils.
肠道微生物群可提供保护，抵御砷（As）诱导的毒性，并且砷代谢被认为是与土壤砷暴露相关的风险评估的重要组成部分。然而，关于微生物铁（III）还原及其在人体肠道中土壤结合态砷代谢中的作用，我们知之甚少。在这里，我们确定了偶然摄入受污染土壤中砷和铁的溶解与转化情况，它是粒径（<250μm、100 - 250μm、50 - 100μm和<50μm）的函数。用人体肠道微生物群进行结肠培养产生了高度的砷还原，甲基化率分别高达53.4和0.074μg/（log CFU/mL）/小时；甲基化百分比随着土壤有机质的增加和土壤孔隙尺寸的减小而增加。我们还发现显著的微生物铁（III）还原以及高水平的亚铁（Fe(II)）（占总可溶性铁的48% - 100%）可能会促进砷甲基化的能力。尽管在低铁溶解和高铁/砷摩尔比的情况下未观察到铁相的统计变化，但结肠阶段较高的砷生物可及性（平均29.4%）主要源于含砷（V）的铁（III）（羟基）氧化物的还原溶解。我们的结果表明，人体肠道微生物群（携带arrA和arsC基因）对砷的迁移和生物转化受到微生物铁（III）还原与土壤粒径耦合的强烈控制。这将扩展我们对土壤砷的口服生物利用度以及接触受污染土壤所带来的健康风险的认识。
