【摘要】 环境中的抗生素残留将胁迫农作物根际土壤微生物产生耐药性,使得这些农作物的根际土壤成为抗性基因转移的"热区"。采用陆生微宇宙系统,模拟玉米生长过程中大环内酯类抗生素进入植物根际土壤后相应抗性基因的分布情况。利用实时荧光定量PCR（qPCR）技术分析了63 d内玉米根际土壤中大环内酯类抗生素抗性基因（erms）的相对丰度（erms∶16S rDNA,即erms绝对浓度与16S rDNA绝对浓度的比值）。结果显示:土壤中不同抗性基因相对丰度存在较明显的差异,整体表现为ermF>ermX>ermB>ermC。7 d时,非根际（BK）土壤中ermB、ermC、ermF和ermX相对丰度分别为4.72×10^-2、1.98×10^-3、7.13×10^-1和1.75×10^-2,而63 d时则分别为1.74×10^-3、3.24×10^-4、3.53×10^-3和2.28×10^-3,基因相对丰度增幅分别为-96.3%、-83.6%、-99.5%和-87.0%;根际（RH）土壤中ermB、ermC、ermF和ermX相对丰度增幅分别为-88.3%、103.0%、-88.6%和71.5%,暗示玉米根际可能具有促进土壤中抗性基因ermC和ermX增殖或转移的作用。不同深度土层中erms相对丰度由大到小依次为0～0.2、>0.2～0.4和>0.4～0.6 m,表明erms在土壤中具有向下迁移的特性,且随着土壤深度的增加,相对丰度呈递减趋势;与未种植玉米（CK）土壤相比,种植玉米（MA）土壤中erms检出率和相对丰度较高,表明玉米的根际环境有利于不同类型erms的富集以及在剖面土壤中的纵向迁移。更多还原

【Abstract】 Antibiotic residues in crop soils create selection pressure on the occurrence and dissemination of antibiotic resistance genes（ARGs）, rendering rhizosphere soils "hot spots" for ARGs. In the present study, the soil microbiome was monitored for macrolide resistance genes（erms） arising from the rhizosphere in maize during different crop growth periods over a duration of 63 days using real-time polymerase chain reaction（PCR） technology. The relative abundance（erms∶16 S rDNA） of erms in the soil was in the order of ermF > ermX > ermB > ermC. The relative abundance of ermF, ermX, ermB, and ermC in bulk soil were 4.72 × 10^-2, 1.98 × 10^-3, 7.13 × 10^-1, and 1.75×10^-2, respectively, on D7, whereas, on D63, the relative abundance were 1.74 × 10^-3, 3.24 × 10^-4, 3.53 × 10^-3 and 2.28 × 10^-3, respectively. The corresponding gene proliferation rates in bulk soil were-96.3%,-83.6%,-99.5%, and-87.0%, respectively, compared to-88.3%, 103.0%,-88.6%, and 71.5%, respectively, in rhizosphere soil. These results suggest that the maize rhizosphere had a significant effect on the proliferation or transfer of ermC and ermX. The relative abundance of erms at different soil depths was in the order of 0-0.2, > 0.2-0.4, and > 0.4-0.6 m, indicating that the resistance genes had a downward migration tendency, with relative abundance of resistance genes decreasing with an increase in soil depth. The detection rate of resistance genes at corresponding depths of soil for the same sample was in the order of RH > CK, suggesting that the presence of the plant rhizosphere not only promotes an increase in resistance gene abundance in the soil but also promotes vertical migration in the soil profile.更多还原