School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Yangtze River Delta Eco-environmental Change and Management Observation and Research Station, Ministry of Science and Technology, Shanghai 200240, China.
Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
Environ Int. 2024 Mar;185:108517. doi: 10.1016/j.envint.2024.108517. Epub 2024 Feb 22.
The organoarsenical feed additive roxarsone (ROX) is a ubiquitous threat due to the unpredictable levels of arsenic (As) released by soil bacteria. The earthworms representing soil fauna communities provide hotspots for As biotransformation genes (ABGs). Nonetheless, the role of gut bacteria in this regard is unclear. In this study, the changes in As speciation, bacterial ABGs, and communities were analyzed in a ROX-contaminated soil (50 mg/kg As in ROX form) containing the earthworm Eisenia feotida. (RE vs. R treatment). After 56 d, earthworms reduced the levels of both ROX and total As by 59 % and 17 %, respectively. The available As content was 10 % lower in the RE than in R treatment. Under ROX stress, the total ABG abundance was upregulated in both earthworm gut and soil, with synergistic effects observed following RE treatment. Besides, the enrichment of arsM and arsB genes in earthworm gut suggested that gut bacteria may facilitate As removal by enhancing As methylation and transport function in soil. However, the bacteria carrying ABGs were not associated with the ABG abundance in earthworm gut indicating the unique strategies of earthworm gut bacteria compared with soil bacteria due to different microenvironments. Based on a well-fit structural equation model (P = 0.120), we concluded that gut bacteria indirectly contribute to ROX transformation and As detoxification by modifying soil ABGs. The positive findings of earthworm-induced ROX transformation shed light on the role of As biomonitoring and bioremediation in organoarsenical-contaminated environments.
有机胂饲料添加剂洛克沙胇（ROX）是一种普遍存在的威胁，这是由于土壤细菌释放的砷（As）含量不可预测。蚯蚓作为土壤动物群落的代表，为砷生物转化基因（ABGs）提供了热点。尽管如此，肠道细菌在这方面的作用尚不清楚。在这项研究中，分析了含有赤子爱胜蚓（Eisenia feotida）的 ROX 污染土壤（ROX 形式的 As 含量为 50mg/kg）中砷形态、细菌 ABGs 和群落的变化（RE 与 R 处理）。56d 后，蚯蚓将 ROX 和总 As 的水平分别降低了 59%和 17%。RE 处理下的土壤中有效 As 含量比 R 处理低 10%。在 ROX 胁迫下，蚯蚓肠道和土壤中总 ABG 丰度均上调，RE 处理后观察到协同效应。此外，蚯蚓肠道中 arsM 和 arsB 基因的富集表明，肠道细菌可能通过增强土壤中 As 的甲基化和转运功能来促进 As 的去除。然而，携带 ABGs 的细菌与蚯蚓肠道中 ABG 丰度无关，这表明由于不同的微环境，蚯蚓肠道细菌与土壤细菌具有独特的策略。基于拟合良好的结构方程模型（P=0.120），我们得出结论，肠道细菌通过改变土壤 ABGs 间接促进 ROX 转化和 As 解毒。蚯蚓诱导的 ROX 转化的积极发现为有机胂污染环境中的 As 生物监测和生物修复提供了启示。
