摘要

      由于抗生素和金属耐药机制相似，人们越来越担心环境中金属污染可能会导致耐药基因（ARGs）的选择。在这里，我们构建了短期的实验室微观结构，以研究在铜浓度梯度（0~1000mg kg-1）下农业土壤中ARGs和两个铜（Cu）抗性基因的动态变化。流动基因元件（MGEs）也被量化为ARGs水平基因转移潜能的一个指标。利用高容量定量PCR技术检测了126种土壤中的ARGs，其中多药耐药和β-内酰胺耐药是最为丰富的ARG类型。铜的加入显著提高了ARGs和MGEs的绝对丰度和相对丰度，并随Cu浓度的增加而逐渐增加。两个铜抗性基因（copA和pcoR）在低浓度铜处理（50和100mg kg-1）中高度富集，其丰度随铜浓度的增加而降低。随着时间的推移，所有铜处理的金属和抗生素抗性水平逐渐下降，但经过56天的培养，污染土壤中的金属和抗生素抗性水平仍明显高于未处理土壤。网络分析显示ARGs与MGEs之间存在显著的相关性，表明Cu改良土壤中抗生素抗性的迁移潜力。ARGs与铜抗性基因之间未发现显著的正相关，表明这些基因不在同一细菌宿主中。综上所述，我们的研究结果提供了经验证据，表明短期铜胁迫可导致高水平抗生素和金属抗性的进化，并显著改变土壤ARGs的多样性、丰度和水平转移潜力。

       Owing to the similar mechanisms of antibiotic and metal resistance, there is a growing concern that metal contamination may select for antibiotic resistance genes (ARGs) in the environment. Here, we constructed short-term laboratory microcosms to investigate the dynamics of a wide range of ARGs and two copper (Cu) resistance genes in an agricultural soil amended with a gradient of Cu concentrations (0~1000 mg kg^-1). Mobile genetic elements (MGEs) were also quantified as a proxy for the horizontal gene transfer potential of ARGs. We detected 126 unique ARGs across all the soil samples using the high-capacity quantitative PCR array, and multidrug and β-lactam resistance were the most abundant ARG categories. The copper amendments significantly enhanced the absolute and relative abundances of ARGs and MGEs, which gradually increased along the gradient of increasing Cu concentrations. The two Cu resistance genes (copA and pcoR) were highly enriched in low-level Cu treatment (50 and 100 mg kg^-1), and their abundances decreased with the increasing Cu concentrations. The level of metal and antibiotic resistance gradually declined over time in all Cu-amended treatments but was still considerably higher in contaminated soils than untreated soils after 56 days' incubation. Significant associations among ARGs and MGEs were revealed by the network analysis, suggesting the mobility potential of antibiotic resistance in Cu-amended soils. No significant positive correlations were found between ARGs and copper resistance genes, suggesting that these genes are not located in the same bacterial hosts. Taken together, our results provide empirical evidence that short-term copper stress can cause evolution of high-level antibiotic and metal resistance and significantly change the diversity, abundance, and horizontal transfer potential of soil ARGs.

       https://link.springer.com/article/10.1007%2Fs11356-018-2978-y