The environment is increasingly recognized as an important reservoir for antibiotic resistance genes (ARGs). Mediated at the genetic level, ARGs are regarded as contaminants of emerging concern, and environmental stressors prompting horizontal gene transfer of ARGs are known to include antibiotics and are hypothesized to include certain metals. Because wastewater, which contains both metals and ARGs, can be reclaimed for agriculture, the fate of ARGs and metals in soils is important to understand. In this work, the extent of influence that copper concentrations exert over ARG proliferation and decay rates are explored through a longitudinal microcosm study design. Soil-fertilizer microcosms using commercially available fertilizer were created and monitored for levels of ARGs and the mobile genetic element intI1. Decay of four ARGs from microcosms at four concentrations was monitored over a period of 30 days (n=240). Influence of copper inoculation at 0, 5, 50 and 100mg/L was observed to influence ARG decay over 30 days with highest variability observed at day 12 and for gene sul1. While many copper amended microcosms decayed to comparable quantities as the no metal control, copper amendment did alter the ARG content in garden soil amended microcosms at the completion of 30 days. The control microcosms (no added metal) had undetectable sul1 levels, while microcosms amended with 50 and 100mg/L copper had quantifiable ARG levels. The dynamics of other ARGs as well as intI1 were also studied. These results point to the importance of metal co-contaminants in the proliferation of ARGs.

Fate of antibiotic resistance genes and intI1 in soil and fertilizer microcosms at varying levels of copper

2019 Fall National Meeting

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