Determining the Potential of Soil Communities to Metabolize Emerging Environmental Contaminants using Metagenomics

Thelusmond, Jean-Rene, Alison M. Cupples, Timothy Strathmann
Michigan State University, Colorado School of Mines, Golden, CO

Presented at the All Scientist Meeting and Investigators Field Tour (2017-10-06 to 2017-10-07 )

It is now widely recognized that pharmaceuticals and personal care products (PPCP) are not fully eliminated in wastewater treatment plants (WWTPs). This is a cause for concern because of the use of wastewater effluents for irrigation and the application of biosolids as nutrient amendments to agricultural soils. PPCP persistence in soils poses a risk for water contamination or uptake into crops and eventual unintended human consumption. PPCP biodegradation by soil microorganisms is a potential removal mechanism; however, the bacteria and pathways involved are generally unknown. Such information is critical to protect natural systems from long-term PPCPs contamination. This research focuses on PPCP biodegradation in agricultural soils. The targeted PPCP are commonly found in WWTP effluents and biosolids and include diclofenac (DFC) (2-(2,6-dichloranilino) phenylacetic acid, DCF), carbamazepine (CBZ) (5H-dibenzo [b,f]azepine-5-carboxamide, CBZ), triclocarban (TCC) (3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea and triclosan (TSC) (5-chloro-2-(2,4-dichlorophenoxy)phenol). The objectives were to determine which microorganisms and pathways are associated with PPCP biodegradation in a number of agricultural soils. The first study involved four soils collected from an agricultural site close to MSU. The second (and on-going) study focuses on soils from each of the plots for Treatments 1, 2, 3 and 4 within the Main Cropping System Experiment at KBS LTER. In the first study, limited CBZ or DCF biological removal was noted under anaerobic conditions; however, CBZ and DCF biodegradation was observed under aerobic conditions. Several phylotypes were enriched following biodegradation, compared to the controls, and these are considered putative degraders. Several pathways were statistically more enriched during biodegradation (KEGG pathway of “xenobiotic degrading genes” for CBZ and “metabolism of valine, leucine and isoleucine” for DCF), suggesting these pathways are important for the biodegradation of these pharmaceuticals in agricultural soils. The experiments from the soils from KBS LTER are still ongoing.

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