College of Environment and Ecology, Hunan Agricultural University, Changsha, 410128, PR China.
Department of Environmental Sciences, The University of Haripur, Haripur, Pakistan.
Environ Pollut. 2023 Jun 1;326:121488. doi: 10.1016/j.envpol.2023.121488. Epub 2023 Mar 21.
Numerous studies have revealed the spread mechanism of antibiotic resistance genes (ARGs) in single antibiotic-contaminated soils. However, the comprehensive impacts of heavy metals and antibiotics on ARGs and the underlying mechanisms are still unknown. Here, high-throughput quantitative PCR and high-throughput sequencing were used to investigate changes in ARGs and bacterial communities under various sulfamethoxazole (SMX) regimes (0, 1, 10, 50 mg kg) in arsenic (As) contaminated soils. The study found that the abundances of ARGs, mobile genetic elements (MGEs), and heavy metal resistance genes (HMRGs) significantly increased in the soil fortified at 10 and 50 mg kg SMX concentrations. The ARGs abundance increased with the increase in the MGEs abundance. Many significant positive correlations between various ARGs subtypes and HMRGs subtypes were found. These results indicate that the HMRGs and MGEs positively contributed to the enrichment of ARGs in As-contaminated soils under SMX stress. Meanwhile, the abundance of copiotrophic (Actinobacteriota) reduced and oligotrophic (Gemmatimonadota) increased, indicating that the life history strategy of the community changed. In addition, Gemmatimonadota was positively correlated to ARGs, HMRGs, and MGEs, suggesting that Gemmatimonadota, which can cope with As and SMX stress, was the host for resistance genes in the soil. Finally, the study found that MGEs play a determinant role in ARGs proliferation due to the direct utilization of HGT, and the indirect effect for ARGs spread under a co-selection mechanism of ARGs and HMRGs, while the bacterial community showed indirect influences by altering environmental factors to act on MGEs. Collectively, this study revealed new insights into the mechanisms of resistance gene transmission under combined SMX and As contamination in soil ecosystems.
大量研究揭示了抗生素耐药基因（ARGs）在单一抗生素污染土壤中的传播机制。然而，重金属和抗生素对 ARGs 的综合影响及其潜在机制尚不清楚。在此，采用高通量定量 PCR 和高通量测序技术，研究了在砷（As）污染土壤中不同磺胺甲恶唑（SMX）浓度（0、1、10、50 mg kg）下磺胺甲恶唑对 ARGs 和细菌群落的影响。研究发现，在 10 和 50 mg kg SMX 浓度下，土壤中 ARGs、移动遗传元件（MGEs）和重金属抗性基因（HMRGs）的丰度显著增加。ARGs 的丰度随着 MGEs 丰度的增加而增加。发现各种 ARGs 亚型和 HMRGs 亚型之间存在许多显著的正相关关系。这些结果表明，在 SMX 胁迫下，砷污染土壤中，HMRGs 和 MGEs 对 ARGs 的富集起积极作用。同时，富养型（Actinobacteriota）的丰度减少，贫养型（Gemmatimonadota）的丰度增加，表明群落的生活史策略发生了变化。此外，Gemmatimonadota 与 ARGs、HMRGs 和 MGEs 呈正相关，表明能够应对 As 和 SMX 胁迫的 Gemmatimonadota 是土壤中抗性基因的宿主。最后，研究发现 MGEs 通过直接利用 HGT 在 ARGs 增殖中起决定作用，以及通过 ARGs 和 HMRGs 的共选择机制对 ARGs 传播的间接作用，而细菌群落通过改变环境因素对 MGEs 产生间接影响。总的来说，本研究揭示了在土壤生态系统中，SMX 和 As 联合污染下，抗性基因传播的机制的新见解。
