New classes of emerging contaminants including pharmaceuticals, antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs) have received increasing attention due to the rapid increase in their abundance in the environment. As consumption of food crops is a direct exposure pathway of pharmaceuticals, ARB, and ARGs to human gut microbiome, it is important to understand the changes in bacterial community and ARG profiles in food crops produced with contaminated soils and waters. In this study, we examined the level and type of ARGs and the composition of bacterial community in the soil, and the shoots and roots of lettuce under soil surface or overhead irrigation with pharmaceuticals-contaminated water. We used high throughput quantitative PCR to detect 142 ARGs and mobile genetic elements (MGEs) and 16S rRNA sequencing to determine bacteria community composition. Our results showed that ARG profiles and bacterial community were sensitive to the pharmaceutical exposure via irrigation water. MGE <i>intl1</i> was consistently more abundant with the pharmaceutical exposure than in the absence of pharmaceuticals. <i>Methylophilaceae</i> was enriched with the pharmaceutical exposure. Pharmaceutical exposure decreased bacterial alpha diversity. There was significant interplays among bacteria community, antibiotic concentrations, and ARG abundance. Soil surface irrigation could decrease the abundance of ARGs and the bacterial diversity in the lettuce shoot. Thus, our results suggest that managing the use of antibiotics and irrigation methods can help minimize the dissemination of ARGs in crop production.

Pharmaceutical exposure changed bacterial community and antibiotic resistance gene profiles in surface- and overhead-irrigated greenhouse lettuce

256th National Meeting (2018)

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