Biology subjects

Desparmet, A.

Publications and source records attributed to Desparmet, A..

4 recordsLinked to original sources

bioRxiv2026

Pigment and isoprostanoid responses to cold atmospheric plasma-induced oxidative conditions in a natural epipelic diatom assemblage

Intertidal mudflats hosting diatom-dominated microphytobenthic communities experience strong variability in environmental conditions, which can lead to cellular oxidative stress. These constraints can, in some cases, affect diatom metabolism and photosynthetic performance in the short term, potentially compromising their survival and even leading to cell death. This study investigates pigment, isoprostanoid, and photophysiological changes in a diatom assemblage originating from a natural microphytobenthic biofilm under different durations of helium-oxygen bubbling cold atmospheric plasma experimental treatments, mimicking complex oxidative conditions of the environment. To this end, 2-min and 5-min treatments were applied to the diatom assemblage, and metabolic parameters were monitored over time up to +180 min after plasma treatment cessation. Despite physicochemical changes and slight perturbations in metabolite profiles induced by plasma treatments, photosynthetic capacities of the diatoms remained largely preserved. The duration-dependent effects of plasma treatments induced selective and mostly reversible changes, primarily characterized by an increase in the relative proportions of pheopigments and a decrease in the relative proportions of {beta}-carotenes following the 5-min treatment. A transient decrease in the relative proportions of the isoprostanoids 10-F4t-neuroP and 5-F2t-IsoP was also observed. By exposing natural diatom assemblage to plasma-generated oxidative conditions, this study provides novel insights into how marine microbiome respond to oxidative perturbations, contributing to our understanding of diatom success in fluctuating intertidal environments.

biophysics↗

bioRxiv2026

Motile epipelic diatoms exhibit dynamic aggregation behaviour altered under oxidative perturbation

Epipelic diatoms continuously adjust their position within sediments, yet how individual motility contributes to the spatial organization and temporal dynamics of collective aggregation and how this behaviour responds to environmental conditions remain poorly understood. We resuspended a natural assemblage dominated by Pleurosigma strigosum and Gyrosigma balticum in filtered seawater and monitored aggregation dynamics over 72 h under a dark control condition or under 24 h exposure to a nominal initial H2O2 concentration of 400 umol L-1, followed by a 48 h post-exposure period. Time-lapse imaging and quantitative image analysis revealed rapid aggregation and continuous remodeling into dynamic, spatially complex multicellular networks. In the control, aggregate number declined from 11,767 to 3,237 and surface coverage from 24.4% to 10.3%, with pronounced temporal fluctuations. Under H2O2, aggregation followed a distinct, less variable trajectory, with fewer aggregates and persistent differences following the cessation of H2O2 exposure. These observations suggest that dynamic aggregation behaviour may contribute to biofilm organization and resilience, while not distinguishing active regulation from emergent cell-cell-matrix interactions.

microbiology↗

bioRxiv2026

Red and blue light cues drive contrasting remodeling of lipophilic metabolites and photophysiology in natural benthic diatom biofilms

Intertidal mudflats are low hydrodynamic energy environments hosting microphytobenthic communities that experience strong spatiotemporal variability in light regimes, including changes in spectral quality and light intensity that can lead to cellular photooxidative stress. To cope with these fluctuations, autotrophs exhibit diverse and highly plastic adaptations that are often species-dependent and shaped by their ecological niches. This study investigates photophysiological responses and metabolic remodeling in a diatom assemblage originating from a natural winter microphytobenthic biofilm under contrasting red and blue light intensities. To this end, photosynthetic parameters were monitored alongside changes in lipophilic metabolites, including untargeted lipids and lipophilic pigments. While few metabolites showed temporal remodeling, rapid and contrasting changes were observed within 30 minutes in response to both spectral quality and light intensity. Red light treatments induced broader remodeling of lipophilic metabolites than blue light, whereas blue light appeared to have a greater impact on photosynthetic parameters. Moreover, red light induced xanthophyll-cycle responses comparable to those observed under blue light at equivalent incident intensity. We discuss these metabolic responses in relation to diatom photoadaptive strategies, placing these findings within the intertidal environmental framework. This work further underlines the importance of understanding rapid metabolic plasticity in coping with light fluctuations, providing new insights into the photoregulatory strategies of natural microphytobenthic communities.

cell biology↗

bioRxiv2025

Reactive oxygen species drive downward vertical migration in diatom microphytobenthic biofilms as a strategy to cope with oxidative stress

Diatom-dominated intertidal microphytobenthic biofilms experience daily fluctuations in irradiance, which can lead to oxidative stress within the photosynthetic apparatus through the production and accumulation of reactive oxygen species. To maintain photosynthetic efficiency, benthic diatoms have developed protective strategies, including mobilization of the antioxidant xanthophyll cycle and the ability to migrate vertically through sediments. However, mechanistic understanding of signaling pathways underlying migration remains poorly characterized. This study investigated the triggering effect of reactive oxygen species on behavioral and photophysiological responses through the analysis of lipophilic pigments and fluorescence parameters. To this end, two microphytobenthic communities, one with sediment allowing vertical migration and another without sediment restricting it, were exposed to irradiance, cold atmospheric plasma, and hydrogen peroxide stresses. Results showed a consistent downward migration response under all oxidative stresses, highlighting the key role of reactive oxygen species, especially hydrogen peroxide, in triggering this microphytobenthic behavior. Moreover, a difference was observed between the pathways involved in vertical migration and those underlying photoprotective responses. Hydrogen peroxide and cold atmospheric plasma stresses highlighted the necessity for substantial microphytobenthic migration, whereas irradiance induced a specific and controlled response involving engagement of the xanthophyll cycle, acting in synergy with the migration strategy by showing stronger activation when migration was impaired. By establishing that a rapid and efficient migration could be induced by reactive oxygen species and could act in synergy with the xanthophyll cycle in epipelic cells, this study provides key insights into the molecular basis of microphytobenthic responses to cellular and environmental oxidative stresses.

ecology↗