Citric acid secretion from rice roots contributes to reduction and immobilization of Cr(VI) by driving microbial sulfur and iron cycle in paddy soil

文献类型： 外文期刊

第一作者： Xiao, Wendan

作者： Xiao, Wendan;Zhang, Qi;Zhao, Shouping;Chen, De;Gao, Na;Huang, Miaojie;Ye, Xuezhu

作者机构： Zhejiang Acad Agr Sci, State Key Lab Managing Biot & Chem Threats Qual &, Key Lab Informat Traceabil Agr Prod, Inst Agroprod Safety & Nutr, Hangzhou 310021, Peoples R China

关键词： Cr(VI) reduction; Root exudate; Citric acid; Sulfate-reducing bacteria; Sulfide-oxidizing bacteria; Fe(III)-reducing bacteria

期刊名称：SCIENCE OF THE TOTAL ENVIRONMENT （ 2022影响因子：9.8； 五年影响因子：9.6 ）

ISSN： 0048-9697

年卷期： 2023 年 854 卷

页码：

收录情况： SCI

摘要： Root exudates released by plants can promote microbial growth and activity, thereby affecting the transformation and availability of soil pollutants. However, the effects of the root exudates of rice plants on chromium (Cr) transformation in paddy soils and the underlying mechanisms are yet to be elucidated properly. The present study investigated how rice root exudates interact with rhizosphere microorganisms to influence the transformation of Cr and explored the key components in root exudates that affect Cr(VI) reduction. The results showed that the addition of root exudate and citric acid markedly decreased soil pH and increased dissolved organic carbon content that created favorable con-ditions and provided sufficient electron donors for Cr(VI) reduction, thereby greatly facilitating the reduction of Cr(VI) and the transformation of HOAc-extractable Cr into more stable oxidizable and residual Cr. Additionally, Desulfovibrio- related sulfate-reducing bacteria, Thiobacillus-related sulfide-oxidizing bacteria, and Geobacter-related Fe(III)-reducing bacteria were enriched with the addition of root exudate and citric acid. Among them, sulfate would be reduced by Desulfovibrio to sulfide, which would be further utilized by Thiobacillus to reduce Cr(VI), thereby enabling the contin-uous reduction of Cr(VI); simultaneously, Geobacter would sustain the reduction of Cr(VI) by reducing Fe(III) to Fe(II). Furthermore, based on the high-level secretion of citric acid in response to Cr(VI) exposure and the similar effects of root exudates and citric acid on Cr(VI) reduction, it is proposed that citric acid is the key component in rice root exu-dates that affects Cr(VI) reduction. These results suggest that root exudates (citric acid as the key component) contrib-ute to the reduction and immobilization of Cr(VI) by driving microbial S and Fe cycles, with Desulfovibrio, Thiobacillus, and Geobacter being the keystone genera. The study provides a novel insight into the Fe/S/Cr co-transformation processes with microbial involvement, and the artificial root exudate mixtures designed to reduce Cr(VI).

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