摘要

长期大量施用杀菌剂导致土壤残留污染，进而改变土壤微生物群落。然而，目前尚不清楚残留杀菌剂是否会影响温室土壤中抗药性基因（ARGs）的多样性和丰度。在实验室条件下，用鸟枪基因组测序法测定了温室和山地土壤中杀菌剂的消散及其对ARGs丰度的影响。结果表明，温室土壤比山地土壤具有更多的多样性和丰富的ARGs。多菌灵、嘧菌酯和百菌清的施用可以增加温室土壤中总ARG的含量，特别是对优势ARG亚型sul2、sul1、aadA、tet（L）、tetA（G）和tetX2的含量有显著影响。温室土壤中丰富的ARGs与可移动基因元件（MGEs，如inti1和R485）显著相关，而山地土壤中则无显著相关。同时，通过对温室土壤中宏基因组整合的基因排布遗传分析，进一步验证了ARGs与MGEs（sul2与R485、sul1与transpasse）的共现模式。此外，寄主追踪分析表明，ARGs主要由温室土壤中的肠杆菌携带，而山区土壤中的则由放线菌携带。这些结果证实了一些杀菌剂可能作为ARGs的辅选择剂，并通过MGEs介导的水平基因转移提高了ARGs的丰度。

Long-term substantial application of fungicides in greenhouse cultivation led to residual pollution in soils and then altered soil microbial community. However, it is unclear whether residual fungicides could affect the diversity and abundance of antibiotic resistance genes (ARGs) in greenhouse soils. Here, the dissipation of fungicides and its impact on the abundance of ARGs were determined using shotgun metagenomic sequencing in the greenhouse and mountain soils under laboratory conditions. Our results showed the greenhouse soils harbored more diverse and abundant ARGs than the mountain soils. The application of carbendazim, azoxystrobin, and chlorothalonil could increase the abundance of total ARGs in the greenhouse soils, especially for those dominant ARG subtypes including sul2, sul1, aadA, tet(L), tetA(G), and tetX2. The abundant ARGs were significantly correlated with mobile genetic elements (MGEs, e.g. intI1and R485) in the greenhouse soils but no significant relationship in the mountain soils. Meanwhile, the co-occurrence patterns of ARGs and MGEs, e.g., sul2 and R485, sul1 and transposase, were further verified via the genetic arrangement of genes on the metagenome-assembled contigs in the greenhouse soils. Additionally, host tracking analysis indicated that ARGs were mainly carried by enterobacteria in the greenhouse soils but actinomyces in the mountain soils. These findings confirmed that some fungicides might serve as the co-selectors of ARGs and elevated their abundance via MGEs-mediated horizontal gene transfer in the greenhouse soils.

https://www.sciencedirect.com/science/article/pii/S0269749119354843