Metabolomic responses of freshwater periphytic microbiome to combined stress of artificial light at night (ALAN) and benzalkonium chloride
Résumé
Urban activities can be a threat for ecosystem sustainability. For instance, there are numerous
findings about the adverse effects of anthropogenic chemicals released from urban treatment
plants on freshwater periphytic communities, which play key role in ecosystems function and
associated services. Despite this increasing evidence, there a still a paucity of knowledge on the
effect of chemicals combined to other anthropogenic stress. Among them, of particular concern
is the Artificial Light At Night (ALAN). Thus, through ten days exposure of freshwater periphyton
in controlled conditions, we have recently highlighted the combined effect of ALAN and
benzalkonium chloride (i.e. main component of alcohol-based hand sanitizers) on
photosynthetic function, diatoms morphology and pigment composition whereas the associated
molecular/biochemical mechanisms/responses remained unknown. In this context, the present
study aims to fill this gap of knowledge by providing metabolomic insights on this combined
effect. To this end, following the same experiment the metabolome and the lipidome were
characterized. In particular, high-resolution mass spectrometry based-untargeted metabolomics
was implemented in order to provide a comprehensive picture of the microbial activities (i.e.
molecular phenotype) and identify biochemical pathways involved in the physiological and
morphological impairments. In addition, targeted analysis of key class of lipids (phospholipids,
glycerolipids, fatty acids) was performed to highlight potential effect on energy storage and
chloroplast/thylakoid membranes. Preliminary results show clear effect of both individual factors
and their combination through the discovery of specific metabolome fingerprints and associated
pathways that change over exposure time. Complementary analyses are still ongoing. The
results highlight as well a shift in the composition of targeted lipid classes following exposure to
(e.g. unsaturation rates of polar lipids). Overall, this study confirms the relevance of
metabolomics/lipidomics approaches to provide mechanistic understanding of the response of
environmental microbiomes to multiple stress, further supporting the discovery of biomarkers of
ecosystem function impairment along the adverse outcomes pathway framework.