摘要
      叶层是抗生素抗性基因（ARGs）的重要库，但ARGs从土壤和空气向叶层的转移机制尚不清楚。本研究表明，土壤-空气叶层是ARG的主要转移途径，通过薄膜覆盖阻断它可以使生菜中典型的叶层ARG减少80.7%-98.7%（平均89.5%）。为了进一步消除覆膜生菜中的叶层ARGs，土壤内部叶层转移途径值得更多关注。我们通过Illumina Nanopore杂交测序分析了地膜覆盖下生菜根际和叶际的ARG宿主和抗性组。假单胞菌7SR1比其他ARG宿主更丰富，分别占根际和叶际细菌总数的1.0%和47.1%。该物种的鞭毛可以促进移动性，并可以排泄细胞外聚合物和/或表面活性剂类微生物产物，这有利于其在叶层的定殖。阻止假单胞菌7SR1通过土壤内层-叶层途径的迁移将有效地进一步减少叶层中的ARGs。多药耐药基因在叶层中占主导地位（占总数的40.3%），87.6%的叶层ARGs位于染色体上，表明水平基因转移（HGT）潜力相对较低。本研究深入了解了典型植物叶际ARGs的转移机制、宿主和控制策略。
Abstract
Phyllosphere is an important reservoir of antibiotic resistance genes (ARGs), but the transfer mechanism of ARGs from soil and air to phyllosphere remains unclear. This study demonstrated that soil-air-phyllosphere was the dominant ARG transfer pathway, and blocking it by film mulching can reduce typical phyllosphere ARGs in lettuce by 80.7% - 98.7% (89.5% on average). To further eliminate phyllosphere ARGs in lettuce grown with film mulching, the internal soil-endosphere-phyllosphere transfer pathway deserves more attention. We analyzed the ARG hosts and the resistome in lettuce rhizosphere and phyllosphere with film mulching via hybrid Illumina-Nanopore sequencing. Pseudomonas sp. 7SR1 was more abundant than other ARG hosts, accounting for 1.0% and 47.1% of the total bacteria in rhizosphere and phyllosphere, respectively. The species has flagella that can promote mobility and can excrete extracellular polymeric substances and/or surfactant-like microbial products, which benefits its colonization in the phyllosphere. Impeding the migration of Pseudomonas sp. 7SR1 via the soil-endosphere-phyllosphere pathway would be effective to further reduce ARGs in phyllosphere. Multidrug resistant genes were predominant in phyllosphere (40.3% of the total), and 87.6% of the phyllosphere ARGs were located on chromosomes, indicating relatively low horizontal gene transfer (HGT) potentials. This study provides insights into the transfer mechanism, hosts, and control strategies of phyllosphere ARGs in typical plants.

https://www.sciencedirect.com/science/article/abs/pii/S1001074221001728