Soil is an important reservoir of antibiotic resistance genes (ARGs) and understanding how corresponding environmental changes influence their emergence, evolution, and spread is crucial. The soil-dwelling bacterial genus Listeria, including L. monocytogenes, the causative agent of listeriosis, serves as a key model for establishing this understanding. Here, we characterize ARGs in 594 genomes representing 19 Listeria species that we previously isolated from soils in natural environments across the United States. Among the five putatively functional ARGs identified, lin, which confers resistance to lincomycin, is the most prevalent, followed by mprF, sul, fosX, and norB. ARGs are predominantly found in Listeria sensu stricto species, with those more closely related to L. monocytogenes tending to harbor more ARGs. Notably, phylogenetic and recombination analyses provide evidence of recent horizontal gene transfer (HGT) in all five ARGs within and/or across species, likely mediated by transformation rather than conjugation and transduction. In addition, the richness and genetic divergence of ARGs are associated with environmental conditions, particularly soil properties (e.g., aluminum and magnesium) and surrounding land use patterns (e.g., forest coverage). Collectively, our data suggest that recent HGT and environmental selection play a vital role in the acquisition and diversification of bacterial ARGs in natural environments.

土壤是抗生素耐药基因 （ARG） 的重要储存库，了解相应的环境变化如何影响它们的出现、进化和传播至关重要。土壤中的细菌属李斯特菌，包括李斯特菌病的病原体 L. monocytogenes，是建立这种理解的关键模型。在这里，我们在代表 19 种李斯特菌的 594 个基因组中表征了 ARGs，我们之前从美国自然环境中的土壤中分离出这些物种。在已鉴定的 5 种推定功能性 ARG 中，赋予林可霉素耐药性的 lin 最普遍，其次是 mprF、sul、fosX 和 norB。ARGs 主要存在于严格意义上的李斯特菌物种中，那些与单核细胞增生李斯特菌关系更密切的物种往往含有更多的 ARGs。值得注意的是，系统发育和重组分析提供了最近在物种内和/或跨物种的所有五个 ARGs 中水平基因转移 （HGT） 的证据，这可能是由转化介导的，而不是结合和转导。此外，ARGs 的丰富度和遗传分化与环境条件有关，特别是土壤特性（例如铝和镁）和周围的土地利用模式（例如森林覆盖率）。总的来说，我们的数据表明，最近的 HGT 和环境选择在自然环境中细菌 ARG 的获取和多样化中起着至关重要的作用。