不同施肥类型对蔬菜地土壤抗生素抗性基因和细菌群落结构的影响

Effect of fertilizer types on antibiotic resistance genes and bacterial community in vegetable fields

  • 摘要: 农田土壤生态系统是抗生素抗性基因(ARGs)的源与汇, 畜禽粪便施用是土壤中ARGs的重要来源。畜禽粪便在蔬菜地土壤中的大量施用, 加剧了蔬菜地土壤ARGs的污染, 对人类健康造成潜在危害。本文采集了河北省不同施肥类型(施用鲜鸡粪、鲜羊粪、鲜牛粪、商品有机肥以及单施化肥)的蔬菜地表层土壤(0~20 cm)样品, 采用定量PCR技术和高通量测序技术对蔬菜地土壤ARGs和细菌群落结构开展了研究, 旨在探究不同施肥类型蔬菜地土壤中ARGs的分布特征及其影响因素。结果表明, 不同施肥类型蔬菜地土壤中均检测到较高丰度的四环素类ARGs (tetA、tetC、tetG、tetL、tetO、tetM、tetW、tetQ)、磺胺类ARGs (sul1、sul2)以及Ⅰ类整合酶基因(intI1), 其中所有施肥处理土壤中磺胺类ARGs总绝对丰度高达9.96×109 copies∙g−1(干土), 且显著高于四环素类ARGs总丰度1.07×109 copies∙g−1(干土)。畜禽粪肥和化肥的施用都显著增加了土壤中ARGs丰度, 其中高化肥施加量土壤中ARGs检出丰度最高6.34×109 copies∙g−1(干土), 商品有机肥土壤中ARGs检出丰度最低3.09×108 copies∙g−1(干土)。施畜禽粪肥土壤中细菌群落的Shannon指数和Chao1指数显著高于高化肥施加量土壤, 但与低化肥施加量土壤差异不显著, 说明畜禽粪肥施用显著提高了土壤细菌群落的α多样性。Pearson相关性分析结果表明, 细菌群落结构是影响ARGs分布的重要因素。IntI1基因与sul2tetGtetQ以及tetW基因呈显著正相关(P<0.05), 说明intI1基因在ARGs的传播和扩散中也起着重要作用。本研究结果表明高化肥施用量能显著增加蔬菜地土壤ARGs的丰度, 商品有机肥的施用对土壤ARGs丰度影响最小。本研究为评估不同施肥类型蔬菜地土壤中ARGs的污染现状提供了相应的数据参考。

     

    Abstract: Farmland ecosystems are essential sources and sinks of antibiotic resistance genes (ARGs), and the application of livestock manure is a major contributor to ARGs in soil. The massive application of livestock manure to vegetable fields has intensified the pollution caused by ARGs in soil. Raw consumption of edible vegetables is one of the most direct ways to introduce ARGs from the soil–plant system to humans, which poses a potential threat to human health. However, few studies have investigated the effects of different fertilizer types on ARGs and bacterial communities in vegetable fields. In this study, 21 soil samples (0–20 cm) were collected from vegetable fields in Hebei Province using different fertilizer types (fresh fowl manure, fresh sheep manure, fresh cattle manure, commercial organic fertilizer, and chemical fertilizer). The distributions and characteristics of ARGs and bacterial communities in vegetable fields were investigated using real-time quantitative polymerase chain reaction (PCR) and high-throughput sequencing techniques. Eight tetracycline resistance genes (tetA, tetC, tetG, tetL, tetO, tetM, tetW, and tetQ), two sulfonamide resistance genes (sul1 and sul2), and one intI1 gene were detected in all vegetable fields. The absolute abundance of sulfonamide resistance genes (9.96×109 copies·g−1 in dry soil) was significantly higher than that of tetracycline resistance genes (1.07×109 copies·g−1 in dry soil). The application of livestock manure and chemical fertilizer both significantly increased the abundance of ARGs in vegetable fields. The highest abundance of ARGs (6.34×109 copies∙g−1 in dry soil) was found in vegetable fields with higher chemical fertilizer amendment, while the lowest abundance of ARGs (3.09×108 copies∙g−1 in dry soil) was found in vegetable soil with commercial organic fertilizer. In addition, the Shannon and Chao1 indices, representing the α diversity of the soil bacterial community, were significantly higher in soil fertilized with livestock manure compared to high-chemical fertilizer application but not in low-chemical fertilization soil, indicating that livestock manure application significantly increased the abundance and diversity of the soil bacterial community. Pearson’s correlation analysis showed that soil bacterial community structure was an important factor influencing the distribution of ARGs. Proteobacteriota, Bacteroidota, Actinobacteriota, and Firmicutes were the dominant potential hosts of ARGs and were significantly correlated with sulfonamide and tetracycline resistance genes (P<0.05). The distribution of ARGs was also affected by soil organic matter and total nitrogen content. The intI1 gene had significant and positive correlations with the sul2, tetG, tetQ, and tetW genes, suggesting its crucial role in ARGs dissemination. In the present study, the use of higher concentrations of chemical fertilizers led to a significantly increased abundance of ARGs in the soil of vegetable fields, whereas the application of commercial organic fertilizers had the least effect on ARGs abundance. This study serves as a guide for evaluating the status of ARGs pollution in vegetable fields with different fertilizer types.

     

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