Periodic Reporting for period 1 - PhytoPharm (Phytotoxicological Risk of pharmaceuticals in soils)
Reporting period: 2017-08-01 to 2019-07-31
The PEC mixture was then used in a 4 month mesocosm study using Spring Barley (Hordeum vulgare) as model plant species. Over the course of the experiment, mesocosms were watered twice weekly, to supplement rainfall, with synthetic wastewater effluent containing antibiotics at PEC, 0.1xPEC 10xPEC, 100xPEC, or 0. Soil samples were collected at the start of the study, prior to irrigation with antibiotics, 16 hours after the first antibiotic exposure, 8 weeks of routine antibiotic exposure, and at plant maturity at 16 weeks. The fate of antibiotics was measured in soil-pore water and mesocosm leachate. Plant development endpoints were measured in both below and above ground biomass and included biomass, stem height, tiller and leaf counts, and grain production. Soil samples were collected to monitor microbial community structure and development of AMR genes using high-throughput qPCR. Throughout the experiment, the Skyline 2-D fly-by-wire device, developed at the University of York, was employed to continuously monitor greenhouse gas fluxes including CO2, N20, and methane. Stable isotope analysis was performed on plant leaves pre and post fertilization to measure shifts in the natural abundance of N15 and C13, as indicators for plant stress. A metabolomics approach was conducted to measure differences in the plant extractable metabolome of grain produced under the different exposure regimes.
Furthermore, this study is among the first to utilize plant metabolomics to investigate the impact of chemical exposure. While the tool has been demonstrated for other environmental stressors, i.e. drought and salinity, we have demonstrated that it can be useful to measure the impacts of antibiotic exposure on an economically important crop.
In totality, we have shown that barley is most sensitive to antibiotic exposure in early growth stages. Over time and in the absence of other stressors, e.g. nutrient limited conditions, that plants demonstrated little residual effects at the time of harvest and by inference were able to overcome contaminant stress. This knowledge can be used in the development of best management practices for agricultural production. Where possible, crops should be initially grown with fresh water prior to introduction of contaminants via wastewater.