奶牛养殖粪水施用量对农田土壤中抗生素抗性基因赋存特征及微生物群落结构的影响

Effects of the irrigation amount of dairy wastewater on the characteristic of antibiotics resistance genes and microbial community structure in farmland soil

为探究奶牛养殖粪水施用对农田土壤中抗生素抗性基因(Antibiotics Resistance Gene,ARGs)赋存特征及微生物群落结构的影响,本研究以经氧化塘处理后的奶牛养殖粪水为研究对象,设置4组不同的养殖粪水施用量,分别为0、0.016、0.032和0.064 t·m^(-2),在玉米农田连续施用2个玉米生长周期后采集土壤,利用荧光定量PCR技术和高通量测序分析土壤中ARGs的丰度及微生物群落结构.研究发现施用养殖粪水后土壤中ARGs总相对丰度显著(p<0.05)提高了0.85~5.41倍.土壤中ARGs和可移动基因元件(Mobile Genetic Elements,MGEs)的总相对丰度均与养殖粪水施用量呈显著正相关(p<0.05),tet C、sul2和erm B是影响ARGs总丰度变化的主导基因.相较于养殖粪水施用为0 t·m^(-2)时,养殖粪水施用量从0.016 t·m^(-2)增加到0.064 t·m^(-2)时,土壤中微生物群落的chao1指数分别增加了44.4%、47.5%和42.3%,说明养殖粪水施用增加了土壤中微生物群落的物种丰富度,但粪水施用量增加未改变土壤微生物群的β多样性.VPA分析表明微生物群落、土壤理化和MGEs三者的交互作用对ARGs丰度变化的贡献率最大为46.4%,其次是微生物群落为20.9%.施用养殖粪水会显著增加土壤中ARGs的丰度和细菌物种丰富度,在一定范围内粪水施用量增加也会造成ARGs和MGEs丰度增加.

Experiment was conducted in maize filed to investigate the changes of antibiotics resistance genes(ARGs)and microbial community in the farmland soil irrigated with treated livestock wastewater(TLWW)from oxidation ponds.Application amounts of 0,0.016,0.032 t·m^(-2),and 0.064 t·m^(-2)TLWW were used in this experiment.Soil samples were analyzed by using fluorescence quantitative PCR and high-throughput sequencing after two consecutive maize growth cycles with different amounts of TLWW.Results showed that the total relative abundance of ARGs was significantly increased by 0.85~5.41 times(p<0.05)in soil irrigated with TLWW.The amount of TLWW was significantly correlated with the total relative abundance of mobile genetic elements(MGEs)and ARGs in soil(p<0.05).the dominant ARGs found were tetC,sul2,and ermB.Compared with control test(0 t·m^(-2)),the Chao1 index indicated an increasein species richness of bacteria by 44.4%,47.5%and 42.3%,when the application amount increased from 0.016 t·m^(-2)to 0.064 t·m^(-2),but had little effect on onβ-diversity of microbial community.Variance Partitioning Analysis(VPA)results showed that the interaction effects of microbial community,soil physicochemical and MGEs contributed most to the change of ARGs abundance,at a rate of 46.4%,followed by microbial community(20.9%).This study suggests that the application of TLWW increases both the total relative abundance of ARGs and bacterial species richness,while also increasing MGE levels within soils irrigated with it through oxidation ponds treatment.