Diversity and abundance of antibiotic resistance genes in rhizosphere soil and endophytes of leafy vegetables: Focusing on the effect of the vegetable species

Abstract

Antibiotic resistance genes (ARGs) in the endophytes of vegetables represent a potential route of human exposure to the soil resistome. However, the effect of vegetable species on the endophytic ARG profiles is unclear, hampering our understanding of how ARGs migrate into the soil-vegetable system and their potential health risks. Here, we planted four leafy vegetables (cilantro, endive, lettuce, and pak choi), which are commonly eaten raw, and analyzed the resistomes and microbiomes in three sample types (rhizosphere soil, root, and leaf endophytes). A total of 150 ARG subtypes were detected using high-throughput quantitative PCR. Vegetable species had a significant effect on ARG diversity and abundance, and pak choi accumulated more ARGs in its associated microbiome than the other three vegetables. The bacterial community was the primary factor shaping ARG profiles and was significantly correlated with ARG subtypes. We identified aadE, tet(34), and vanSB as shared ARGs among leaves of the four vegetables; the bacterial families correlated with tet(34) and vanSB were also shared across the vegetables and belonged to Proteobacteria. This study deepens our understanding of how endophytic ARG profiles vary among different vegetables and highlights the potential health risk associated with consuming these vegetables raw.