Biology subjects

Le Faucheur, S.

Publications and source records attributed to Le Faucheur, S..

5 recordsLinked to original sources

bioRxiv2024

Cobalt induces the set-up of new structural network in river biofilms: Impairment of autotrophic-heterotrophic coupling.

Biofilms play a crucial role in biogeochemical cycles, making them essential to the functionality and stability of aquatic ecosystems. Their functioning is mainly driven by interactions between microorganisms that ensure the cycling of major elements. Evaluating the impact of stressors, such as metals, on these interactions is challenging. This study examined the effects of cobalt (Co) on the microeukaryotic community and their relationships with prokaryotes within biofilms grown in the presence of several Co concentrations (background concentrations, 0.1, 0.5, and 1 {micro}M) for 28 days and 35 days after the end of Co injection. A previous work has suggested that Cyanobacteria were highly sensitive to Co leading to a reduction of the photosynthetic potential of the biofilm. In this study, the major primary producers, namely Bacillariophyceae, were also found to be sensitive to Co. The direct consequence of this sensitivity was an impairment of the autotroph-heterotroph coupling and the dominance of prokaryotic taxa in microbe-microbe interactions. The biofilms co-occurrence networks were then smaller, less connected but more centralized at 1 {micro}M Co. Keystones, that were half affiliated with microalgae in the absence of Co, were mostly prokaryotes. As such, prokaryotes were found to control resource production and element cycling in Co-stressed biofilms. These changes in co-occurrence network organization and microbial community composition demonstrated a cascade of effects related to contamination in rivers. Our results further highlighted the strategy biofilms adopt to counteract the impairment of autotroph-heterotroph coupling, and to maintain their functions and ecosystemic roles in contaminated environments.

ecology↗

bioRxiv2024

Cobalt effects on prokaryotic communities living in growing river biofilms: impact on their colonization kinetics, structure and functions.

1.Although cobalt (Co) is widely used in the transition to low-carbon energy technologies, its environmental impact remains almost unknown. This study examines Co impacts on the prokaryotic communities of river biofilms to assess their potential use as bioindicators of Co contamination. To that end, biofilms were grown on blank glass slides placed in artificial streams enriched with Co (0.1, 0.5 and 1 {micro}M Co) for 28 days and prokaryotic abundance and diversity were analyzed using DNA-metabarcoding every 7 days. The resilience of the prokaryotic community was investigated after a further 35 days without Co contamination. Prokaryotic communities were impacted by 0.5 and 1 {micro}M Co from the beginning of the biofilm colonization. Although biofilms reached similar biomasses regardless of Co concentration, control biofilms were dominated by Cyanobacteria and Planctomycetes while Bacteroidetes dominated Co contaminated biofilms. Potential functional redundancy was observed with the implementation of carbon fixation alternatives by non-photosynthetic prokaryotes in biofilms subjected to high Co concentrations. No structural resilience of the biofilms was observed after 35 days without Co contamination. The use of prokaryotic community response measured using molecular approaches appears to be a promising and cost-effective approach for assessing changes in water quality due to metals. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/592147v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@d72d70org.highwire.dtl.DTLVardef@e83c80org.highwire.dtl.DTLVardef@dc002borg.highwire.dtl.DTLVardef@18f481e_HPS_FORMAT_FIGEXP M_FIG C_FIG SynopsisFew knowledge is available about Co ecotoxicity in freshwaters. This study assess the potential of prokaryotic communities developing in freshwater biofilms to be used as bioindicator of Co contamination.

molecular biology↗

bioRxiv2023

New sensitive tools to characterize meta-metabolome response to short- and long-term cobalt exposure in dynamic river biofilm communities

Untargeted metabolomics is a non-a priori analysis of biomolecules that characterizes the metabolome variations induced by short- and long-term exposures to stressors. Even if the metabolite annotation remains lacunar due to database gaps, the global metabolomic fingerprint allows for trend analyses of dose-response curves for hundreds of cellular metabolites. The combination of untargeted metabolomic features and benchmark-dose (BMD) calculations then makes it possible to determine concentration range inducing defense responses (CRIDeR) and concentration range inducing damage responses (CRIDaR). To develop this approach in a context of time-dependent microbial community changes, mature river biofilms were exposed for 1 month to four cobalt (Co) concentrations (background concentration, 1 x 10-7, 5 x 10-7 and 1 x 10- 6 M) in an open system of artificial streams. The meta-metabolomic response of biofilms was compared against a multitude of biological parameters (including bioaccumulation, biomass, chlorophyll a content, composition and structure of prokaryotic and eukaryotic communities) monitored at set exposure times (from 1 hour to 28 days). Cobalt exposure induced extremely rapid responses of the meta-metabolome, with time range inducing defense responses (TRIDeR) of around ten seconds, and time range inducing damage responses (TRIDaR) of several hours. Even in biofilms whose structure had been altered by Co bioaccumulation (reduced biomass, chlorophyll a contents and changes in the composition and diversity of prokaryotic and eukaryotic communities), CRIDeRs with similar initiation thresholds (1.41 {+/-} 0.77 x 10-10 M Co2+ added in the exposure medium) were set up at the meta-metabolome level at every time point. In contrast, the CRIDaR initiation thresholds increased by 10 times in long-term Co exposed biofilms. The present study demonstrates that defense and damage responses of biofilm meta-metabolome exposed to Co are rapidly and sustainably impacted, even within tolerant and resistant microbial communities. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=77 SRC="FIGDIR/small/567369v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@e7a87eorg.highwire.dtl.DTLVardef@e712b7org.highwire.dtl.DTLVardef@7de128org.highwire.dtl.DTLVardef@493053_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIProkaryotic community structures were impacted after 1 h of exposure to Co C_LIO_LIBiofilm meta-metabolome was impacted after 36 s of exposure to Co C_LIO_LIBiofilm meta-metabolome response was faster than changes in biofilm communities C_LIO_LIShort- and long-term exposed biofilms have similar CRIDeR initiation thresholds C_LIO_LILong-term exposed biofilms have higher CRIDaR initiation thresholds C_LI

molecular biology↗

bioRxiv2023

How do biomarkers dance? Specific moves of defense and damage biomarkers for biological interpretation of dose-response model trends.

Omics and multi-omics studies are currently increasingly used in ecotoxicology to highlight the induction of known or new biomarkers when an organism is exposed to one (or more) contaminant(s). Although it is virtually impossible to identify all biomarkers from all possible organisms, biomarkers can be grouped into two categories, defense or damage biomarkers and they have a limited number of response trends. Our working hypothesis is that defense and damage biomarkers show different dose-response patterns. A meta-analysis of 156 articles and 2,595 observations of dose-response curves of well-known defense and damage biomarkers was carried out in order to characterize the response trends of these biological parameters in a large panel of living organisms (18 phyla) exposed to a wide variety of inorganic or organic contaminants. Defense biomarkers describe biphasic responses (bell-shaped and U-shaped) to a greater extent than damage biomarkers. In contrast, damage biomarkers varied mainly monotonically (decreasing or increasing). Neither the nature of the contaminant nor the type of organisms, whatever the kingdom (Plantae, Animalia, Chromista or Bacteria), influence these specific responses. This result suggests that cellular defense and damage mechanisms are not specific to stressors and are conserved throughout life. The meta-analysis results confirm the usefulness of trend analysis in dose-response models as a biological interpretation of biomarkers in large dataset and their application in determining the concentration ranges inducing defense responses (CRIDeR) and the concentration ranges inducing damage responses (CRIDaR) regardless of the contaminant tested or the organism studied. HighlightsO_LIWe interpreted 2,595 biomarker dose-response curves generated by chemical exposure. C_LIO_LIDefense biomarkers mainly describe biphasic (bell- or U-shaped) trends. C_LIO_LIDamage biomarkers mainly describe monotonic (decreasing or increasing) trends. C_LIO_LICellular defense and damage responses appear to have been conserved during evolution. C_LIO_LIResponse trend analysis is a promising tool for environmental risk assessment. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=77 SRC="FIGDIR/small/551999v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@14b19c4org.highwire.dtl.DTLVardef@188ae31org.highwire.dtl.DTLVardef@643ed6org.highwire.dtl.DTLVardef@15953cd_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

Meta-metabolomic Responses of River Biofilms to Cobalt Exposure and Use of Dose-response Model Trends as an Indicator of Effects

Metabolites are low molecular-weight molecules produced during cellular metabolism. The global expression of the meta-metabolome (metabolomics at the community level) could thus potentially be used to characterize the exposure of an organism or a community to a specific stressor. Here, the meta-metabolomic fingerprints of mature biofilms were examined after 1, 3 and 7 days of exposure to five concentrations of cobalt (0, 1 x 10-7, 1 x 10-6, 5 x 10-6 and 1 x 10-5 M) in aquatic microcosms. The global changes in meta-metabolomic fingerprints were in good agreement with those of the other biological parameters studied (cobalt bioaccumulation, biomass, chlorophyll content). To better understand the dose-responses of the biofilm meta-metabolome, the untargeted LC-HRMS metabolomic data were further processed using the DRomics tool to build dose-response model curves and to calculate benchmark doses (BMD). These BMDs were aggregated into an empirical cumulative density function. A trend analysis of the metabolite dose-response curves suggests the presence of a concentration range inducing defense mechanisms (CRIDeM) between 4.7 x 10-7 and 2.7 x 10-6 M, and of a concentration range inducing damage mechanisms (CRIDaM) from 2.7 x 10-6 M to the highest Co concentration. The present study demonstrates that the molecular defense and damage mechanisms can be related to contaminant concentrations and represent a promising approach for environmental risk assessment of metals. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=94 SRC="FIGDIR/small/545533v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@179fd06org.highwire.dtl.DTLVardef@1d2cd10org.highwire.dtl.DTLVardef@9508a3org.highwire.dtl.DTLVardef@6a1818_HPS_FORMAT_FIGEXP M_FIG C_FIG SYNOPSISThis study focuses on the interpretation of the metabolite dose-response trends in river biofilms exposed to cobalt to identify concentration range inducing cellular mechanisms and improve the environmental risk assessment of metals.

microbiology↗