Pharmaceutical exposure changed antibiotic resistance genes and bacterial communities in soil-surface- and overhead-irrigated greenhouse lettuce

• Published in: Environment international Vol. 131; p. 105031
• Main Authors: Shen, Yike, Stedtfeld, Robert D., Guo, Xueping, Bhalsod, Gemini D., Jeon, Sangho, Tiedje, James M., Li, Hui, Zhang, Wei
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.10.2019; Elsevier
• Subjects: agroecosystems; antibiotic resistance; Antibiotic resistance genes; antibiotics; bacteria; Bacteria - drug effects; bacterial communities; Bacterial community; Chitinophagaceae; community structure; direct contact; Drug Resistance, Microbial - genetics; drugs; food consumption; food crops; Genes, Bacterial; greenhouses; humans; interspersed repetitive sequences; intl1; Irrigation; Lactuca - chemistry; Lactuca - microbiology; Lettuce; Methylophilaceae; multiple drug resistance; overhead irrigation; Pharmaceuticals; polluted soils; quantitative polymerase chain reaction; ribosomal RNA; risk; RNA, Bacterial - analysis; RNA, Ribosomal, 16S - analysis; roots; shoots; Soil Microbiology; Soil Pollutants - analysis; species diversity; Sphingomonadaceae; Water Pollutants - analysis; Irrigation; Lettuce; Antibiotic resistance genes; Bacterial community; Pharmaceuticals; intl1
• ISSN: 0160-4120; 1873-6750; 1873-6750
• DOI: 10.1016/j.envint.2019.105031

New classes of emerging contaminants such as pharmaceuticals, antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs) have received increasing attention due to rapid increases of their abundance in agroecosystems. As food consumption is a direct exposure pathway of pharmaceuticals, ARB, and ARGs to humans, it is important to understand changes of bacterial communities and ARG profiles in food crops produced with contaminated soils and waters. This study examined the level and type of ARGs and bacterial community composition in soil, and lettuce shoots and roots under soil-surface or overhead irrigation with pharmaceuticals-contaminated water, using high throughput qPCR and 16S rRNA amplicon sequencing techniques, respectively. In total 52 ARG subtypes were detected in the soil, lettuce shoot and root samples, with mobile genetic elements (MGEs), and macrolide-lincosamide-streptogramin B (MLSB) and multidrug resistance (MDR) genes as dominant types. The overall abundance and diversity of ARGs and bacteria associated with lettuce shoots under soil-surface irrigation were lower than those under overhead irrigation, indicating soil-surface irrigation may have lower risks of producing food crops with high abundance of ARGs. ARG profiles and bacterial communities were sensitive to pharmaceutical exposure, but no consistent patterns of changes were observed. MGE intl1 was consistently more abundant with pharmaceutical exposure than in the absence of pharmaceuticals. Pharmaceutical exposure enriched Proteobacteria (specifically Methylophilaceae) and decreased bacterial alpha diversity. Finally, there were significant interplays among bacteria community, antibiotic concentrations, and ARG abundance possibly involving hotspots including Sphingomonadaceae, Pirellulaceae, and Chitinophagaceae, MGEs (intl1 and tnpA_1) and MDR genes (mexF and oprJ). [Display omitted] •Surface-irrigated lettuce shoots had low diversity and abundance of ARGs.•Overhead-irrigated shoots had higher α-diversity than surface-irrigated shoots.•Pharmaceuticals enriched Proteobacteria (Methylophilaceae) in all samples.•Pharmaceutical exposure lowed α-diversity in lettuce root, shoot and soil samples.•Hotspots existed in bacterial families and ARGs (intl1, tnpA_1, mexF, oprJ).