The metabolites of light: untargeted metabolomic approaches bring new clues to understand light-driven adaptation of intertidal mudflat biofilm.

Abstract

The microphytobenthos (MPB) is a microbial community of primary producers playing a key role in coastal ecosystem functioning. The intertidal mudflats are subject to challenging variations of irradiance, forcing the micro-organisms to develop photoprotective mechanisms. Two major adaptations to light are well described in literature: the excess of light energy dissipation through non-photochemical quenching (NPQ), and the vertical migration in the sediment. These mechanisms trigger a lot of scientific interest, but the biological processes and metabolic mechanisms involved in light-driven vertical migration remain largely unknown. To our knowledge, this study investigates for the first time metabolomic responses of a migrational mudflat biofilm exposed for 30 min to a light gradient of photosynthetically active radiation (PAR) from 50 to 1000 µmol photons m− 2 s− 1. The untargeted metabolomic analysis allowed to identify metabolites involved in two types of responses to light exposures. On the one hand, the production of FAs from bacterial origin corresponding to good photosynthesis state of MPB under low light (LL) and medium light (ML). On the other hand, alka(e)nes and a fatty alcohol were produced under light-induced stress triggered by high light (HL). The physiological and ecological roles of these compounds are poorly described in literature. This study showed that they seem to play important unexplored roles in light-induced stress adaptation of migrational MPB biofilms. Since alka(e)nes are produced from FAs decarboxylation, these results thus emphasize for the first time the importance of FAs pathways in microphytobenthic biofilms adaptation to light.