Biology subjects

Hubas, C.

Publications and source records attributed to Hubas, C..

9 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↗

bioRxiv2024

Non-enzymatic oxylipin production in a mudflat microphytobenthic biofilm: evidence of a diatom response to light

The microphytobenthos (MPB) is a diatom dominated microbial community of primary producers inhabiting the mudflat sediments. In one hand, the benthic diatoms display photo-protective strategies to face extreme light variations susceptible to generate cellular oxidative stress. In the other hand, oxidative stress induces the production of reactive oxygen species (ROS) that generate oxylipins, oxygenated metabolites of polyunsaturated fatty acids (PUFAs), which are among the known chemical mediators in diatoms. However, non-enzymatically generated oxylipins known as isoprostanoids or isofuranoids are poorly studied in diatoms. To better understand the roles of the latter in migrational MPB light response, we investigated the effect of different light irradiances corresponding to dark (D), low light (LL, 50 and 100 {micro}mol. photons. m-2. s-1PAR), medium light (ML, 250 {micro}mol. photons. m-2. s-1 PAR), high light (HL, 500, 750 and 1000 {micro}mol. photons. m-2. s-1PAR), on the isoprostanoids production by the biofilms organisms. The PUFAs precursors of the varying oxylipins evidenced a diatoms response to light irradiance. Under 1000 PAR condition, the total amount of isoprotanoids increased, indicating an oxidative stress response. Isoprostanes (IsoPs) and prostaglandins (PGs) characterized the HL conditions and evidenced lipid peroxidation probably linked to the higher generation of ROS by the photosynthesis. On the contrary, the phytoprostanes (PhytoPs) characterized the LL and ML where the de-epoxidation state was low and ROS scavengers probably not overwhelmed. This first investigation of non-enzymatic oxylipin production by a microphytobenthic biofilm under different light irradiances highlighted the interest to explore their potential signaling roles related to MPB light responses.

microbiology↗

bioRxiv2024

Limnospira (Cyanobacteria) chemical fingerprint reveals local molecular adaptation

Limnospira can colonize a wide variety of environments (e.g., freshwater, brackish, alkaline or alkaline-saline water) and develop dominant and even permanent blooms that limit over-shadowed adjacent phototrophs diversity, especially in alkaline and saline environments. Previous phylogenomic analysis of Limnospira allowed us to distinguish two major phylogenetic clades (I and II) but failed to clearly segregate strains according to their respective habitats in terms of salinity or biogeography. In the present work, we attempt to determine whether Limnospira displays metabolic signatures specific to its different habitats, particularly brackish or alkaline-saline ecosystems, and question the impact of accessory gene repertoires on respective chemical adaptations. The study of the metabolomic diversity of 93 strains of Limnospira from the Paris Museum Collection, grown under standardized lab culture conditions, showed clearly distinct chemical fingerprints that were correlated with the respective biogeographic origins of the strains. The molecules that most distinguish the different Limnospira geographic groups are sugars, lipids, peptides, photosynthetic pigments, and antioxidant molecules. Interestingly, these molecule enrichments might represent adaptation traits to the local conditions encountered in their respective sampling environments concerning salinity, light and oxidative stress. We hypothesize that within extreme environments, such as those colonized by Limnospira, a large set of flexible genes can provide remarkable adaptation to specific local environmental conditions (e.g., salinity, light, and oxidative pressure). Thus, the occurrence within Limnospira population genomes of a specific set of flexible genes potentially involved in the production of certain metabolites may provide valuable adaptative traits that may support the bloom persistence beyond environmental condition variations. ImportanceLimnospira are ubiquitous cyanobacteria able to colonize and dominate a wide range of alkaline-saline environments around the world according to remarkable adaptative strategies. Phylogenomic analysis of Limnospira platensis allowed to distinguish two major phylogenetic clades (I and II) but failed to clearly segregate strains following their habitats in terms of salinity or biogeography. One can presume that the genes found within this variable portion of the genome of these clades could be involved in L. platensis adaptation to local environmental conditions. In the present paper, we attempt to determine whether Limnospira platensis displays metabolic signatures specific to its different habitats, particularly brackish or alkalinesaline ecosystems, and question the impact of accessory gene repertoire on respective chemical adaptation.

microbiology↗

bioRxiv2022

Identification of microbial exopolymer producers in sandy and muddy intertidal sediments by compound-specific isotope analysis

Extracellular polymeric substances (EPS) refer to a wide variety of high molecular weight molecules secreted outside the cell membrane by biofilm microorganisms. In the present study, EPS from marine microphytobenthic biofilms were extracted and their isotope ratios were analysed. A comparison of these ratios with the carbon isotope ratios of fatty acid biomarkers allowed the identification of the main EPS producers of two contrasting types of intertidal marine sediments. Our study reveals that EPS sources are more diverse in sandy sediments than in muddy sediments. We also found distinct patterns in the production and breakdown of EPS in sandy and muddy environments. The main difference observed was in how epipelic and epipsammic diatoms affected the chemistry of EPS, which had significant implications for the growth of bacteria specialized in utilizing EPS. These differences were likely linked to variations in the functioning of epipelic and epipsammic communities, specifically in how EPS was used either for motility or for cell attachment.

ecology↗

bioRxiv2021

Photosynthesis from stolen chloroplasts increases sea slug reproductive fitness

Some sea slugs are able to steal functional chloroplasts (kleptoplasts) from their algal food sources, but the role and relevance of photosynthesis to the animal host remain controversial. While some researchers claim that kleptoplasts are slowly digestible snacks, others advocate that they enhance the overall fitness of sea slugs much more profoundly. Our analysis show light-dependent incorporation of 13C and 15N in the albumen gland and gonadal follicles of the sea slug Elysia timida, representing translocation of photosynthates to kleptoplast-free reproductive organs. Long-chain polyunsaturated fatty acids with reported roles in reproduction were produced in the sea slug cells using labelled precursors translocated from the kleptoplasts. Finally, we report reduced fecundity of E. timida by suppressing kleptoplast photosynthesis. The present study provides the first thorough experimental evidence that photosynthesis enhances the reproductive fitness of kleptoplast-bearing sea slugs, confirming the biological relevance of this remarkable association between a metazoan and an algal-derived organelle. TeaserSea slugs incorporate functional chloroplasts from algae and use products of photosynthesis to maximize reproductive output.

ecology↗

bioRxiv2020

Trophic niche of the invasive gregarious species Crepidula fornicata, in relation to ontogenic changes

AO_SCPLOWBSTRACTC_SCPLOWThe slipper limpet Crepidula fornicata is a common and widespread invasive gregarious species along the European coast. Among its life-history traits, well documented ontogenic changes in behavior (i.e., motile male to sessile female) suggests a potential shift in feeding strategy across its life stages. Considering the ecological significance of this species in colonized areas, understanding how conspecifics share the trophic resource is crucial. Using fatty acids (FA) and stable isotopes (SI) as complementary trophic markers, we conducted a field survey between late winter and spring to investigate the trophic niche of three ontogenic stages of C. fornicata that bear different sexual (male/female) and motility (motile/sessile) traits. Potential trophic sources were characterized by their pigment, FA and SI compositions and discriminated well over the study period. We showed that the biofilm covering C. fornicata shells harbored a higher biomass of primary producers (i.e., chlorophytes and diatoms) than the surrounding sediment surface. Over the study period, we observed a covariation between the three ontogenic stages for both FA and SI compositions which suggest that the trophic niche of C. fornicata does not change significantly across its benthic life. During periods of low food availability, slipper limpets displayed an opportunistic suspension-feeding behaviour, relying on both fresh and detrital organic matter, likely coming from superficial sedimentary organic matter. During high food availability (i.e., spring phytoplankton bloom), all ontogenic stages largely benefited from this fresh supply of organic matter (pelagic diatoms in this case). However, the three ontogenic stages showed consistent differences in FA composition, and to a lesser extent in SI composition. These differences persist over time, as they originate more likely from ontogenic physiological changes (e.g., differential growth rates, metabolic rate or gametogenesis) rather than diet discrepancies.

ecology↗