Characterization of the metabolomic response of freshwater periphytic biofilm exposed to a serial dilution of glyphosate

Abstract

International audienceGlyphosate is a widely used herbicide detected ubiquitously in European freshwaters. However, there still is a lack of knowledge about its impact on aquatic ecosystems. To fill this gap, periphytic community playing a pivotal role in ecosystem functions, is a relevant model. Also, untargeted meta-metabolomics is an approach of choice through its ability to sensitively characterize the molecular/biochemical phenotype of the community. In this context, this study aims to characterize the meta-metabolome response of periphytic biofilm exposed during 14 days to different concentrations of glyphosate (0.1-150 µg.L-1). The meta-metabolome was characterized by an untargeted approach on a UPLC-HRMS-TOF system. Acquired data were processed in W4M and further analyzed with various chemometric methods. In particular, DROMICS was used to characterize trend (U, Bell, Increase, Decrease) and sensitivity (BMD1sd) of each metabolomic features as well as their aggregated response. Finally, the signals of interest were annotated by combining MS-DIAL and SIRIUS5. Chemometrics revealed that 7276 features reacted to glyphosate. Only 2288 could be annotated. Among them alkaloids (n=662) and amino acids and peptides (n=952) classes were the more reactive. Surprisingly, low effect of glyphosate was noted on the shikimates while this herbicide targets their biosynthesis. DROMICS showed no discrepancy in the proportion of each trend and the sensitivity to glyphosate between the classes. However, the strengh of the response (i.e. fold change) slightly change between the classes, as terpenoids and amino-acids were the most down-regulated classes. Altogether, our results higlighted a complex metabolic response of periphyton to glyphosate that questions potential impairment of ecological functions of these communities