Linking Trace Organic Chemical Attenuation to Microbiome Metabolic Capabilities: Insights from Laboratory- and Full-Scale Managed Aquifer Recharge Systems

Can trace organic chemical biodegradation in complex environments be explained by correlating the behavior of these water pollutants to the expression and abundance of specific enzymes related to their metabolism? In this study, we aim to link trace organic chemical attenuation to the metabolic capability of the microbiome by investigating intermediate xenobiotic transformation products catalyzed by specific enzymes. Water samples from both laboratory- and full-scale managed aquifer recharge systems were analyzed by suspected-target screening using liquid-chromatography time-of-flight mass spectrometry in ESI negative and positive mode. Identification of transformation products was carried out by accurate mass and MS/MS spectra. Out of 75 potential transformation products for 24 parent compounds, six metabolites for six parent compounds were tentatively identified in the analyzed source and groundwater samples. Identified transformation products were compared with the expression and abundance of functional genes quantified by 454 pyrosequencing. For the majority of functional genes involved in xenobiotic degradation pathways, no correlation with environmental parameters such as depth was observed. One important finding of our study is that technical guidelines for standardization of environmental '-omics' research procedures are crucial and should cover amongst others sampling, technical data analysis, and interpretation of results, as well as the definition of cut off criteria, reference points, and normal values.