畜禽粪便堆放地土壤中抗生素抗性基因和细菌群落的垂直分布特征

Vertical distribution of antibiotic resistance genes and bacterial communities in soil of livestock manure stacking site

  • 摘要: 本文通过对养殖场猪粪和鸡粪堆放地0~100 cm土壤样品的采集和分析, 研究了长期堆放畜禽粪便对土壤中抗生素抗性基因(简称“抗性基因”)和细菌群落结构垂直分布的影响。定量PCR结果表明, 与对照土壤相比, 猪粪和鸡粪堆放增加了0~100 cm土壤中四环素类抗性基因(tetCtetGtetLtetW)、磺胺类抗性基因(sulIsulII)以及整合酶基因(intI1)的检出率和检出丰度, 说明粪肥堆放造成堆放地土壤中抗性基因污染。聚类分析结果表明, 抗性基因和intI1基因的丰度随土壤深度呈递减趋势, 且主要集中在0~30 cm土层, 表明堆放地土壤中抗性基因存在向下层土壤迁移的风险。相关性分析表明, intI1基因分别与抗性基因呈显著正相关, 说明intI1基因可能在抗性基因传播中起着重要作用。同时高通量测序结果表明, 与对照土壤相比, 猪粪和鸡粪堆放显著降低了0~10 cm和10~30 cm土层细菌群落结构的多样性, 0~30 cm土层中, 猪粪和鸡粪堆放地土壤中细菌群落结构与对照土壤的差异要高于深层土壤。此外, 方差分解分析结果表明, 土壤化学性质和细菌群落结构均影响了土壤中抗性基因的垂直分布, 且细菌群落结构的变化是其主要的影响因素。本研究可为控制畜禽粪便堆放地土壤中抗性基因污染提供科学依据。

     

    Abstract: Livestock manure has been regarded as an important reservoir of antibiotics and antibiotic resistance genes (ARGs). However, most livestock manure is stacked directly in the farm, which causes a potential threat to the surrounding soil and groundwater safety. In order to study the effect of long-term livestock manure stacking on the vertical distribution of ARGs and bacterial communities, 0−100 cm soil samples were collected from pig and chicken manure stacking sites, respectively. Real-time quantitative PCR results showed that pig and chicken manure stacking increased the detection ratio and abundance of tetracycline resistance genes (tetC, tetG, tetL, tetW) and sulfonamide resistance genes (sulI, sulII), and an integrase gene (intI1) in soil samples. This demonstrated that livestock manure stacking could lead to the contamination of ARGs in the surrounding soil. According to the cluster analysis, the abundance of ARGs and intI1 gene were decreased with increasing soil depth and mainly concentrated in the 0−30 cm soil layer, which posed a risk of migration of ARGs into the deep soil. In addition, intI1 gene had a significant and positive correlation with ARGs abundance, indicating that intI1 gene may play an important role in disseminating ARGs. Furthermore, the high-throughput sequencing results showed that both pig and chicken manure stacking significantly reduced and changed the diversity of bacterial communities in the 0−10 cm and 10−30 cm soil layers, compared with the control soil. The difference of bacterial community structure between livestock manure stacking site soil and control soil was higher in 0−30 cm than in deep soil. What’s more, both soil chemical properties and bacterial community affected the vertical distribution of ARGs in soil, with the shift of bacterial community structure representing the major driver shaping the ARGs distribution based on variation partitioning analysis. Taken together, our results provide insight into the control of ARGs pollution in livestock manure stacking stie soil around the farms.

     

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