摘要

    在温室栽培中长期大量使用杀真菌剂会导致土壤残留污染，进而改变土壤微生物群落。但是，尚不清楚残留的杀真菌剂是否会影响温室土壤中抗生素抗性基因（ARG）的多样性和丰富性。在这里，在实验室条件下，使用shot弹枪宏基因组测序在温室和山区土壤中测定杀菌剂的消散及其对ARGs含量的影响。我们的研究结果表明，温室土壤比山区土壤具有更多的多样性和丰富的ARG。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，特别是对于那些主要的ARG亚型，包括sul2，sul1，aadA，tet（L），tetA（G）和tetX2。温室土壤中丰富的ARG与流动遗传因子（MGEs，例如intI1和R485）显着相关，而在山地土壤中则无显着相关性。同时，通过基因基因在温室土壤中由基因组组装的重叠群上的基因排列，进一步证实了ARG和MGEs的共现模式，例如sul2和R485，sul1和转座酶。此外，宿主跟踪分析表明，ARGs在温室土壤中主要由肠杆菌携带，而在山区土壤中是放线菌。这些发现证实，某些杀真菌剂可作为ARG的共同选择者，并通过MGE介导的温室土壤水平基因转移提高了它们的丰度。 
    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/abs/pii/S0269749119354843