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Metabolomics response kinetics of a periphytic community to mixture of pesticides to unravel short term molecular mechanisms involved in long term structural and functional impairment
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Edité par CCSD -
International audience. Agriculture leads to the release of multiple pesticides into aquatic ecosystems that might be harmful for exposed organisms such as periphytic microbial communities playing a key role in ecosystem functions. Despite evidence about the effect of these chemicals on the structure and functions of periphytic biofilms, there is still a paucity of knowledge about the kinetic of responses. In particular, there is a need to unravel how short term molecular responses are involved in long-term impairment at the functional/structural levels to support the discovery of biomarkers allowing the early and sensitive detection of long term alteration of ecosystem function(s). To this end, untargeted meta-metabolomics is a cutting edge approach since it provides a comprehensive picture of the molecular phenotype of the whole community, as a result of interactions with the environment. In this context, this study aims to characterize the link between the response at the molecular level and the responses at the physiological/function and structural levels of periphytic biofilms exposed during one month to mixture of insectide (fenoxycarb,FNX), herbicide (glyphosate, GLY) and its metabolite (AMPA). At the structural level, normal increase of the biomass was observed between 13 and 28 days in control and FNX conditions while the growth was lower in condition with GLY+AMPA and the mixture. In parallel, there is a decrease of cyanobacteria in control and FNX conditions while they increase following exposure to GLY+AMPA and the mixture. At the physiological level, significant discrepencies were noted for the photosynthetic yield with a decrease after 13 and 28 days of exposure to GLY+AMPA, FNX and the ternary mixture. At the molecular level, HCA showed a clustering of the features according the time as soon as after 4h of exposure. At this time, the effect of the conditions GLY+AMPA is already visible in comparison to other conditions. Further comparison of the significantly modulated features highlighted few overlap between the tested conditions suggesting that specific metabolic pathways were involved in the response. Altogether, our results highlight that the microbial community metabolome changed strongly over time and also responded very quickly to pesticides exposure. This study also suggests specific metabolic pathways involved in the response to FNX vs GLY+AMPA vs FNX+GLY+AMPA, and so likey specific adverse outcome pathways leading to ecological functions impairment.
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