近日，浙江大学唐先进团队揭示了微生物残体碳促进水稻土砷甲基化。2025年11月25日出版的《美国科学院院刊》杂志发表了这项成果。
微生物残体碳（MNC）是土壤有机碳的关键组分。然而，MNC如何调控土壤中微生物的砷（As）甲基化过程仍不清楚。在中国主要稻作区的调查中，细菌和真菌残体碳与转录arsM基因呈显著正相关（P < 0.05）。
研究组利用7种土壤的培养实验，探究了秸秆和三种MNC——革兰氏阳性菌残体碳（G?-NC）、革兰氏阴性菌残体碳（G?-NC）和真菌残体碳（F-NC）——对As甲基化的影响。结果表明，所有类型MNC均增强As甲基化，其中G--NC对甲基化As的积累作用最显著。添加10-60 mg G--NC使土壤孔隙水中As(III)增加43.0%-75.9%，甲基化As含量提升4.4-18.0倍。元基因组和宏转录组分析显示，G--NC添加上调了转录arsM和arsC2基因的相对丰度，这些基因主要归属于酸杆菌门（Acidobacteriota）、变形菌门（Pseudomonadota）、浮霉菌门（Planctomycetota）和拟杆菌门（Bacteroidota）。
值得注意的是，携带arsM基因的甲烷八叠球菌目（Methanosarcinales）和芽孢杆菌目（Moorellales）在目水平的转录活性显著增强。通过促进As还原过程，G--NC为土壤中As甲基化提供了更多底物。此外，G--NC可作为As甲基化微生物的碳源，刺激arsM基因的转录活性，这一机制已通过苯甲酸降解菌（Paraclostridium benzoelyticum TC8）的纯培养实验验证。该研究凸显了MNC在调控As生物地球化学循环中的关键作用，为预测稻田生态系统中As甲基化程度及水稻僵苗病风险提供了理论基础。
附：英文原文
Title: Microbial necromass carbon enhances arsenic methylation in paddy soils
Author: Li, Jie, Gao, Zi-Yu, Chen, Chuan, Liu, Yurong, Zhang, Si-Yu, Xu, Jianming, Zhu, Yong-Guan, Tang, Xianjin
Issue&Volume: 2025-11-25
Abstract: Microbial necromass carbon (MNC) constitutes a critical component of soil organic carbon. Yet, how MNC regulates microbial arsenic (As) methylation processes in soil remains unclear. Across major Chinese rice-growing regions, bacterial and fungal necromass carbon showed significant positive correlations (P < 0.05) with the transcribed arsM gene. Soil incubation experiments with seven soils explored how straw and three types of MNC—gram-positive bacterial necromass carbon (G+-NC), gram-negative bacterial necromass carbon (G-NC), and fungal necromass carbon (F-NC)—affect As methylation. Our results demonstrated that all types of MNC enhanced As methylation, and G-NC exhibiting the most pronounced effect on methylated As accumulation. The addition of 10 to 60 mg G-NC maximally increased As(III) by 43.0 to 75.9% and enhanced methylated As by 4.4- to 18.0-fold in soil porewater vs. the control. Further, metagenomic and metatranscriptomic analyses demonstrated that G-NC addition upregulated the relative abundance of transcribed arsM and arsC2 genes, which were mostly assigned to Acidobacteriota, Pseudomonadota, Planctomycetota, and Bacteroidota. Notably, the transcriptional activity of arsM-harboring Methanosarcinales and Moorellales was markedly enhanced at the order level. By promoting As reduction process, G-NC provides more substrates for As methylation process in soil. Furthermore, G-NC could be used as a carbon source for As-methylating microorganisms, stimulating the transcriptional activity of arsM, which has been confirmed by the incubation experiment with pure culture of Paraclostridium benzoelyticum TC8. This study highlights the critical role of MNC in regulating As biogeochemistry, establishing a basis for predicting the extent of As methylation and risk of rice straighthead disease in paddy ecosystems.
DOI: 10.1073/pnas.2527462122
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2527462122