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Deciphering the tolerance of leaf-associated microbial communities to Kasugamycin through metabolomics and functional descriptors
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Edité par CCSD -
International audience. In the context of agroecology practices, biofungicides have been increasingly used, yet their environmental impact remains poorly documented. In particular, there is a paucity of knowledge about tolerance and resilience of microbial communities to these chemicals while it is critically needed to assess the benefit/risk balance of using these new compounds. To tackle this challenge, meta-metabolomics is an innovative approach in ecotoxicology that provides a snapshot of the molecular phenotype and biochemical processes of a community in response to a contaminant. Additionally, biofilms are highly relevant models in ecotoxicology due to their significant taxonomic and functional diversity, which plays a key role in ecosystems (e.g., biogeochemical cycles). In this context, this study aims to determine the tolerance mechanisms (i.e., tolerance outcome pathway) of leaf litter biofilms to a biofungicide, the kasugamycin (kazu). To this end, biofilms were exposed in controlled conditions during 4 weeks to kazu at 10 mg/L and 100 mg/L. Samplings were performed after 1, 7, 14 and 28 days. Pollution-Induced Community Tolerance (PICT) was implemented at all sampling dates to evaluate the tolerance of the community to the kazu. In parallel, a combination of untargeted metametabolomics approach and structural descriptors (metabarcoding, biomass, ergosterol), as well as physiological/functional descriptors (respiration, β-glucosidase, laccase), was implemented. The results highlighted that kazu led to a decrease in leaf decomposition and bacterial density within the biofilm. A stimulation of β-glucosidase and a reduction in respiration were also observed. Finally, tolerance to kazu was acquired after 7 weeks of exposure, as indicated by changes in laccase activity. However, this acquired tolerance appears to diminish after 28 days of exposure. The results will soon be supplemented by metabolomic and metabarcoding analyses to further understand the biochemical disturbances and microbial biodiversity linked to kazu exposure. By advancing knowledge on the acquisition of tolerance in leaf litter to a biofungicide, molecular descriptors could be identified as specific biomarkers of tolerance, potentially applicable in efforts to preserve aquatic ecosystems.
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