Biology subjects

Duval, C.

Publications and source records attributed to Duval, C..

At least 19 recordsLinked to original sources

bioRxiv2026

Microdiversity drives resilience and niche partitioning in the bloom forming cyanobacteria Limnospira platensis

The intraspecific evolutionary mechanisms of adaptation in blooming cyanobacteria, particularly those occurring on small spatial and temporal scales, remain poorly understood. Here, we used the unique properties of Lake Dziani Dzaha, which hosts a persistent population of Limnospira platensis inhabiting distinct macro-habitats, to explore the spatial and temporal dynamics of microevolution. The Lake Dziani Dzaha (Mayotte), very stable at least since 2010, has experienced a seismo-volcanic crisis from May 2018 to November 2019, characterized by CO2 outgassing that led to the mixing of the initially seasonally stratified water column, as well as changes in numerous physicochemical parameters. Phylogenomic analysis of 108 strains isolated during sampling campaigns in 2010, 2014, 2022, and 2024 revealed a population that remained highly phylogenetically cohesive over time. In 2022, genomic expansion was observed, characterized by an increase in genome size due to the proliferation of insertion sequences and a subsequent loss of adaptive genes. By 2024, a rapid recovery of the 2010-2014 genetic content took place through multiple independent events of horizontal gene transfer. At the spatial scale, although no significant differences in gene content were detected, distinct subpopulations were identified based on allele frequencies. Some alleles were specifically fixed and subject to different selection pressures among the subpopulations, suggesting the existence of distinct ecotypes. Overall, this study highlights the role of microdiversity in rapid resilience of blooming cyanobacteria populations within dynamic environments and in their adaptation through niche partitioning.

microbiology↗

bioRxiv2026

Integrating metagenome-scale metabolic modelling and metabolomics to identify biochemical interactions in Microcystis phycospheres

Favoured by global changes, freshwater cyanobacterial harmful blooms generate major ecological, economical and public health challenges. Microcystis, one of the most widespread cyanobacterial genera, grows within a phycosphere where specialised interactions with its microbiome occur, and are suspected to influence bloom appearance and its potential toxicity. Using a combination of metagenomic, metabolomic and metabolic modelling, we characterised the phycospheres of twelve Microcystis strains isolated from a French pond. The distribution of metabolic reactions within Microcystis was consistent with their genospecies, whereas the metabolic landscape at the community level diverged from cyanobacterial phylogeny indicating functional decoupling between cyanobacteria and their associated microbiomes. Phycosphere-associated bacteria substantially expand the metabolic repertoire of the system, while maintaining functional redundancy within and across communities. On the other hand, metabolomic profiles were largely driven by cyanobacterial metabolic outputs. Metabolic modelling, together with the identification of toxic specialised metabolites produced by specific biosynthetic gene clusters, further highlighted differences in metabolic potential among phycospheres. Together, these findings deepen the understanding of Microcystis phycosphere functioning, demonstrate the value of multi-omics systems biology approaches, and underscore the ecological relevance of interspecies and inter-phycosphere metabolic interactions as a structuring process in bloom-associated microbiomes.

systems biology↗

bioRxiv2025

Higher trophic status leads to more diverse and divergent microeukaryote communities over time in urban lakes from the Greater Paris (France)

Effects of trophic status on lake microeukaryote community dynamics remain underexplored. Spanning oligotrophic to hypereutrophic conditions, peri-urban lakes located in the Greater Paris region (France) offer unique opportunities to compare these dynamics along a eutrophication gradient. Here, community composition was characterized using 18S rRNA gene metabarcoding, and analyzed in the context of environmental parameters and chlorophyll a-derived trophic status throughout an 18-month sampling period. Microeukaryote assemblages were dominated by Cryptophyceae, Spirotrichea, Chrysophyceae, and Chlorophyceae, with mixotrophic and heterotrophic taxa dominating across all lakes. Taxa richness peaked at intermediate trophic levels, consistent with the intermediate disturbance hypothesis. Beta-diversity and network analyses revealed increasing community modularity, reduced connectivity, and enhanced temporal variability with higher trophic status. In lakes reaching the hypereutrophic status, communities diverged progressively over time, suggesting the onset of regime shifts. Conversely, oligo-to mesotrophic lakes maintained more connected and stable assemblages. These findings demonstrate that eutrophication fosters more diverse and increasingly divergent microeukaryote communities, underscoring its role as a central driver of microbial community restructuring in urban freshwater systems.

microbiology↗

bioRxiv2025

Gap junction communication regulates luminal-myoepithelial crosstalk and cell differentiation in a bi-layered human mammary epithelial cell model

Interactions between luminal and myoepithelial cells are essential for proper mammary gland development and function. However, only a few in vitro models allow the study of these interactions and their modulation by extrinsic factors. We developed a layered co-culture system (LCS) that mimics the bilayered architecture of the human breast epithelium, enabling direct contact and bidirectional crosstalk between luminal (MCF-12A) and myoepithelial (MYO1089) cells. We confirmed the formation of adherens and functional gap junctions across the layers. Transcriptomic analysis revealed that co-culture altered gene expression in pathways related to extracellular matrix remodeling, mRNA processing, response to external stimuli, hormonal signaling, receptor activity, and cell cycle regulation. In the LCS, MCF-12A cells exhibited a more luminal-like phenotype, with increased keratin-18 and decreased keratin-14, -smooth muscle actin (-SMA), and caldesmon-1 expression compared to 2D monoculture. Conversely, MYO1089 cells showed enhanced expression of myoepithelial markers, including -SMA, keratin-14, and caldesmon-1. Inhibition of gap junction communication by carbenoxolone disrupted these lineage-specific differentiation patterns. These findings highlight the importance of direct communication in regulating epithelial identity and underscore the LCS as a physiologically relevant model for studying mammary gland biology and external influences that can impact the epithelial differentiation. HighlightsA novel bilayered human co-culture system mimics the luminal and myoepithelial architecture of the mammary epithelium Direct luminal-myoepithelial contact enables formation of functional adherens and gap junctions Direct communication via gap junctions is essential for lineage-specific epithelial differentiation Co-culture induces transcriptional shifts related to proliferation, ECM regulation, and hormone response

cell biology↗

bioRxiv2025

Keratin intermediate filaments mechanically position melanin pigments for genome photoprotection

Melanin pigments block genotoxic agents by positioning on the sun-exposed side of human skin keratinocytes nucleus. How this position is regulated and its role in genome photoprotection remains unknown. By developing a model of human keratinocytes internalizing extracellular melanin into pigment organelles, we show that keratin 5/14 intermediate filaments mechanically control the 3D perinuclear position of pigments, shielding DNA from photodamage. Imaging and microrheology in human disease-related model identify structural keratin cages surrounding pigment organelles to stiffen their microenvironment and maintain their 3D position. Optimum pigment spatialization is required for DNA photoprotection and rely on the interplay between intermediate filaments and microtubules bridged by plectin cytolinkers. Thus, the mechanically-driven proximity of pigment organelles to the nucleus is a key photoprotective parameter. Uncovering how human skin counteracts solar radiation by positioning the melanin microparasol next to the genome anticipates that dynamic spatialization of organelles is a physiological UV stress response. Short summaryMelanin pigments shield DNA from photodamage by positioning atop nuclei in skin keratinocytes. We show keratin 5/14 intermediate filaments control this 3D spatialization, forming protective cages around pigments. This positioning, together with microtubule function, optimizes genome protection, revealing cytoskeletons and organelle dynamics as a UV stress response.

cell biology↗

bioRxiv2025

Off-target genomic effects in MRP8-Cre driver mice complicate its use in weight gain and metabolic studies

BackgroundThromboinflammation of adipose tissue involves accumulation of pro-fibrinogenic factors to adipose tissue in obesity, which promotes immune cell infiltration, affects weight gain and can lead to metabolic dysfunction. The role of neutrophil genes in inflammation are frequently investigated using MRP8-Cre mice to generate neutrophil-specific knockouts. Recent study demonstrated that MRP8-Cre mice have off-target deletions in Serpine1 and Ap1s1 genes. Serpine1, encoding plasminogen activator inhibitor-1, is a key anti-fibrinolytic factor linked to thromboinflammation and metabolic dysfunctions in obesity. In this study, we provide evidence suggesting a critical limitation in using MRP8-Cre model to study adipose tissue, weight-related dysfunctions and/or metabolic disorders. MethodsMRP8-Cre and F13a1-/-MRP8 mice were placed on either control diet or high-fat diet for 16 weeks, with body weight monitored weekly. The expression of Serpine 1, Ap1s1 and Adgre1 (macrophage marker) genes in inguinal and epididymal adipose tissues were analyzed using qRT-PCR and compared to the wild-type mice. ResultsMRP8-Cre shows no Serpine1 or Ap1s1 expression in inguinal and epididymal adipose tissues. MRP8-Cre mouse is resistant to weight gain on obesogenic diet and does not show macrophage marker in adipose tissue compared to control obesity model. The resistance to weight gain translates to a neutrophil knockout model, F13a1-/-MRP8 that was not expected to show resistance to weight gain as its global knockout does not exhibit this phenotype. ConclusionOur work suggests that MRP8-Cre model may not be suitable to investigate metabolic outcomes of neutrophil genes, or pathologies that have underlying etiology in thomboinflammation.

immunology↗

bioRxiv2024

Distinct ecotoxicological impairs induced by different Microcystis genotypes to Medaka fish

One of the most prevalent and notorious bloom-forming freshwater cyanobacterial genus is Microcystis, whom toxicological impairs yet remain incompletely investigated. Based on our previous studies, we hypothesize that some emerging Microcystis metabolites, in addition to microcystins (MCs), are of (eco)toxicological concerns and should be further investigated. To this end, we explore the ecotoxicological potential of different Microcystis genotypes producing various bio-active metabolite cocktails, particularly cyanopeptides of different structural families including MCs, cyanopeptolins, microginins, anabaenopetins, aeruginosins or microcyclamides, on embryo/larvae and adult Medaka fish model. Embryo and larvae exposures to the extracts of the four distinct Microcystis genotypes - comprising two MC-producing (PMC 728.11 and 807.12) and two non-MC-producing (PMC 810.12 and 826.12) strains - showed that PMC 810.12 and 826.12 respectively producing microginins, aeruginosins and microcyclamides exhibit early toxicity and teratogenicity, while PMC 728.11 presented rather larvae toxicity on hatched larvae, in agreement with its high MC content. In addition, we conducted a 4-days microcosm experiment with adult female Medaka exposed to environmental concentrations of these four Microcystis strain cultures to document the microbiome and metabolome responses. Fishes exposed to PMC 728.11 exhibited microbiota dysbiosis signature, while exposure to PMC 826.12 perturbated the fish digestion process inducing even more pronounced microbial and metabolic alterations. The two other strains provoked more moderate perturbations. These findings highlight toxic effects on fish exposed to both MC-as well as non-MC-producing cyanobacteria, suggesting complex interplay and effects of undocumented cyanobacterial bio-active and toxic compounds basides MCs during blooms of Microcystis.

ecology↗

bioRxiv2024

A summer in the Greater Paris: trophic status of peri-urban lakes shapes prokaryotic community structure and functional potential

With more than 12 million inhabitants, the Greater Paris offers a "natural laboratory" to explore the effects of eutrophication on freshwater lakes within a relatively restricted area. Here, a four-month time-series was carried out during summertime to monitor planktonic microbial communities of nine lakes located within a [~]70 km radius around Paris (Ile-de-France, France) of comparable morphologies, yet distinct trophic statuses (mesotrophic to hypereutrophic). The contribution of the trophic status and intra-summer variations were investigated on prokaryotic community structures (16S rRNA gene sequencing) and functions (shotgun metagenomics). Sampled lakes harbored highly distinct and diverse prokaryotic communities. Although their gene pool was quite stable and shared among lakes, taxonomical and functional changes were correlated. The trophic status appears as the main driver of both community structure and functional potential. When focusing on function involved in biogeochemical cycles, responses to phosphorus limitation (mostly polyphosphate-related processes) were highlighted between trophic statuses. Hypereutrophic lakes communities displayed the highest contrast and heterogeneity over time, suggesting a regime shift compared to lakes of lower trophic status. This study explores the influence of eutrophication on lakes microbiome ecology, by comparing for the first time the planktonic microbial communities and their functional potential of lakes of distinct trophic status in close vicinity over a summer season.

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↗

bioRxiv2023

Multi-omics analyses from a single sample: Prior metabolite extraction does not alter the 16S rRNA-based characterization of prokaryotic community in a diversity of sample types

Massive sequencing of the 16S rRNA gene has become a standard first step to describe and compare microbial communities from various samples. Parallel analysis of high numbers of samples makes it relevant to the statistical testing of the influence of natural or experimental factors and variables. However, these descriptions fail to document changes in community or ecosystem functioning. Non-targeted metabolomics are a suitable tool to bridge this gap, yet extractions protocols are different. In this study, prokaryotic community compositions are documented by 16S rRNA sequencing after direct DNA extraction, or after metabolites extraction followed by DNA extraction. Results obtained using the V3-V4 region on non-axenic cultures of cyanobacteria, lake water column, biofilm, gut of wild and lab-reared fish, indicate that prior extraction of metabolites does not influence the obtained image of prokaryotic communities. This validates sequential extraction of metabolites followed by DNA as a way to combine 16S rRNA sequencing with metabolome characterization from a single sample. This approach has the potential to complement community structure characterization with a proxy of their functioning, without the uncertainties associated with the use of separate samples.

microbiology↗

bioRxiv2023

A systematic approach identifies p53-DREAM target genes associated with blood or brain abnormalities

p53 is mainly known as a tumor suppressor, but mouse models revealed that increased p53 activity may cause bone marrow failure, through mechanisms that likely include gene repression mediated by the p53-DREAM pathway. Here we designed a systematic approach to identify p53-DREAM targets whose repression might contribute to abnormal hematopoiesis. We used gene ontology to analyze transcriptomic changes associated with bone marrow cell differentiation and p53 activation, then ChIP-seq data to find promoters bound by the DREAM complex. We next created positional frequency matrices to identify evolutionary conserved sequence elements potentially bound by DREAM. The same approach was developed to find p53-DREAM targets associated with brain abnormalities, also observed in mice with increased p53 activity. Putative DREAM binding sites were found for 151 candidate p53-DREAM target genes, of which 106 are mutated in a blood or brain genetic disorder. Twenty-one DREAM binding sites were tested and found to impact on gene expression in luciferase reporter assays, notably regulating genes mutated in dyskeratosis congenita (Rtel1), Fanconi anemia (Fanca), Diamond-Blackfan anemia (Tsr2), primary microcephaly (Casc5, Ncaph, Wdr62) or pontocerebellar hypoplasia (Toe1). These results provide clues on the role of the p53-DREAM pathway in regulating hematopoiesis and brain development, with implications for tumorigenesis. Author SummaryThe capacity of p53 to activate the transcription of genes important for cell cycle arrest, apoptosis or cellular metabolism has been recognized for decades. By contrast, the potential importance of p53-dependent transcriptional repression emerged more recently. Although p53 frequently appears to repress genes indirectly via the DREAM repressor complex, only a few studies attempted to define p53-DREAM target gene repertoires, often by analyzing cell cycle regulation in fibroblasts. Here we aimed to gain a better appreciation of the clinical relevance of the p53-DREAM pathway by designing a systematic approach for the identification of p53-DREAM targets. Because mouse models with increased p53 activity suffer from bone marrow failure or brain hypoplasia, we relied on transcriptomic changes associated with bone marrow cell differentiation, blood- and brain-related gene ontology terms and RNAseq data from hematopoietic or neural progenitor cells to identify p53-DREAM targets, then created positional frequency matrices to find putative DREAM binding sites. Our study provides a resource of predicted DREAM binding sites for 151 genes associated with blood and/or brain abnormalities, many of which were not previously known to be DREAM targets. Furthermore, our analysis suggests that p53-DREAM alterations may contribute to phenotypic variations in glioblastoma cells.

genetics↗

bioRxiv2023

Lifelong tissue memory relies on spatially organised dedicated progenitors located distally from the injury

It is believed epithelial cells that have participated in a wound repair elicit a more efficient but locally restricted response to future injuries. However here we show that the cell adaptation resulting from a localised tissue damage has a wide spatial impact at a scale not previously noticed. We demonstrate that away from injured site, after a first injury a specific epithelial stem cell population gives rise to long term wound-memory progenitors residing in their own niche of origin. Notably these progenitors have not taken part in the first wound healing but become pre-activated through priming. This adaptation differs from classical features of trained immunity previously shown to be adopted by other epithelial stem cells. Our newly identified wound-distal memory cells display a cell-autonomous transcriptional pre-activated state leading to an enhanced wound repair ability that can be partially recapitulated through epigenetic perturbation even in absence of an injury. Importantly, the harmful consequences of wound repair, such as exacerbated tumorigenesis, occur within these primed cells and follow their spatial distribution. Overall, we show that sub-organ scale adaptation of an injury relies on spatially organised and memory-dedicated progenitors, characterised by an epigenetic actionable cell state, that predisposes to tumour onset.

cell biology↗

bioRxiv2023

Bacterial microbiota of Ostreobium, the coral-isolated chlorophyte ectosymbiont, at contrasted salinities

Microscopic filaments of the siphonous green algae Ostreobium (Ulvophyceae, Bryopsidales) colonize and dissolve the calcium carbonate skeletons of coral colonies, in shallow-water reef environments of contrasted salinities. Their bacterial composition and plasticity in response to salinity remain unknown. Here, we analyzed the bacteria associated with coral-isolated Ostreobium strains from two distinct rbcL lineages, representative of IndoPacific environmental phylotypes, that had been pre-acclimatized (>9months) to three ecologically-relevant reef salinities: 32.9, 35.1 and 40.2 psu. Bacterial phylotypes were visualized at filament scale by CARD-FISH in algal tissue sections, localized to the surface, within filaments or in the algal mucilage. Ostreobium-associated communities, characterized by bacterial 16S rRNA metabarcoding of cultured thalli and corresponding supernatants, were structured by host genotype more than salinity and partly overlapped with those of environmental (Ostreobium-colonized) coral skeletons. Alphaproteobacteria dominated the thalli communities, enriched in Kiloniellaceae or Rhodospirillaceae depending on algal genotype. A small core microbiota composed of 7 ASVs ([~]1.5% of thalli ASVs, 19%-36% cumulated proportions), shared by multiple cultures of both Ostreobium genotypes and persistent across 3 salinities, included putative intracellular Amoebophilus and Rickettsiales bacteria. This novel knowledge on the taxonomic diversity of Ostreobium bacterial associates paves the way to functional interaction studies within the coral holobiont.

genetics↗

bioRxiv2022

Gut microbiota and holobiont metabolome composition of the Medaka fish (Oryzias latipes) are affected by a short exposure to the cyanobacterium Microcystis aeruginosa

Blooms of toxic cyanobacteria are a common stress encountered by aquatic fauna. Evidence indicates that long-lasting blooms affect fauna-associated microbiota. Because of their multiple roles, host-associated microbes are nowadays considered relevant to ecotoxicology, yet the respective timing of microbiota versus functional changes in holobionts response needs to be clarified. The response of gut microbiota and holobionts metabolome to exposure to a dense culture of Microcystis aeruginosa was investigated as a microcosm-simulated bloom in the model fish species Oryzias latipes (medaka). Both gut microbiota and gut metabolome displayed significant composition changes after only 2 days of exposure. A dominant symbiont, member of the Firmicutes, plummeted whereas various genera of Proteobacteria and Actinobacteriota increased in relative abundance. Changes in microbiota composition occurred earlier and faster compared to metabolome composition, suggesting that the microbiota drives the holobionts response. Liver and muscle metabolome were much less affected than guts, supporting that gut and associated microbiota are in the front row upon exposure. This study highlights that even short cyanobacterial blooms, that are increasingly frequent, trigger changes in microbiota composition and holobiont metabolome. It emphasizes the relevance of multi-omics approaches to explore organisms response to an ecotoxicological stress. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/499308v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@112a904org.highwire.dtl.DTLVardef@16589forg.highwire.dtl.DTLVardef@1146629org.highwire.dtl.DTLVardef@3f25e4_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- A 2-day exposure to a simulated M. aeruginosa bloom is enough to sharply decrease the Firmicute/Proteobacteria ratio in the gut of Oryzias latipes fish. - The exposure induced changes in metabolome composition after 2 days in the gut and 4 days in the liver. - The gut bacterial microbiota response occurred faster than metabolomes; we hypothesize that changes in gut microbiota may drive the gut metabolome compositional changes.

microbiology↗

bioRxiv2021

Aberrant Functional Connectivity between Reward and Inhibitory Control Networks in Pre-Adolescent Binge Eating Disorder

BackgroundBehavioral features of binge eating disorder (BED) suggest abnormalities in reward and inhibitory control. Studies of adult populations suggest functional abnormalities in reward and inhibitory control networks. Despite behavioral markers often developing in children, the neurobiology of pediatric BED remains unstudied. Methods58 pre-adolescent children (aged 9-10-years) with BED and 66 age, BMI and developmentally-matched control children were extracted from the 3.0 baseline (Year 0) release of the Adolescent Brain Cognitive Development (ABCD) Study. We investigated group differences in resting-state functional MRI (rs-fMRI) functional connectivity (FC) within and between reward and inhibitory control networks. A seed-based approach was employed to assess nodes in the reward (orbitofrontal cortex, nucleus accumbens, amygdala) and inhibitory control (dorsolateral prefrontal cortex, anterior cingulate cortex) networks via hypothesis-driven seed-to- seed analyses, and secondary seed-to-voxel analyses. ResultsOur findings revealed reduced FC between the dlPFC and amygdala, and between the anterior cingulate cortex and orbitofrontal cortex in pre-adolescent children with BED, relative to age, gender, BMI and developmentally matched controls. These findings indicating aberrant connectivity between nodes of inhibitory control and reward networks were corroborated by the whole-brain FC analyses. ConclusionsEarly-onset BED may be characterized by diffuse abnormalities in the functional synergy between reward and cognitive control networks, without perturbations within reward and inhibitory control networks, respectively. The decreased capacity to regulate a reward-driven pursuit of hedonic foods, which is characteristic of BED, may in part, rest on this dysconnectivity between reward and inhibitory control networks.

neuroscience↗

bioRxiv2021

Disruption of fish gut microbiota composition and holobiont metabolome by cyanobacterial blooms

BackgroundCyanobacterial blooms are one of the most common stress encountered by metazoans living in freshwater lentic systems such as lakes and ponds. Blooms reportedly impair fish health, notably through oxygen depletion and production of bioactive compounds including cyanotoxins. However, in the times of the "microbiome revolution", it is surprising that so little is still known regarding the influence of blooms on fish microbiota. In this study, an experimental approach is used to demonstrate that blooms affect fish microbiome composition and functions, as well as the metabolome of holobionts. To this end, the model teleost Oryzias latipes is exposed to simulated Microcystis aeruginosa blooms of various intensities in a microcosm setting, and the response of bacterial gut communities is evaluated in terms of composition, metagenome-encoded functions and metabolome profiling. ResultsThe gut bacterial community of O. latipes exhibits marked responses to the presence of M. aeruginosa blooms in a dose-dependent manner. Notably, abundant gut-associated Firmicutes almost disappear, while potential opportunists increase. The holobionts gut metabolome displays major changes, while functions encoded in the metagenome of bacterial partners are more marginally affected. Bacterial communities tend to return to original composition after the end of the bloom suggesting post-bloom resilience, and remain sensitive in case of a second bloom, reflecting a highly reactive gut community. ConclusionIn the context of increasingly frequent and intense blooms worldwide, results point to the relevance of accounting for short- and long-term microbiome-related effects in fish ecology, with potential outcomes relevant to conservation biology as well as aquaculture.

microbiology↗

bioRxiv2021

Fibrinogen αC-subregions critically contribute blood clot fibre growth, mechanical stability and resistance to fibrinolysis

Fibrinogen is essential for blood coagulation. The C-terminus of the fibrinogen -chain (C-region) is composed of an C-domain and C-connector. Two recombinant fibrinogen variants (390 and 220) were produced to investigate the role of subregions in modulating clot stability and resistance to lysis. The 390 variant, truncated before the C-domain, produced clots with a denser structure and thinner fibres. In contrast, the 220 variant, truncated at the start of the C-connector, produced clots that were porous with short stunted fibres and visible fibre ends. These clots were mechanically weak and susceptible to lysis. Our data demonstrate differential effects for the C-subregions in fibrin polymerisation, clot mechanical strength, and fibrinolytic susceptibility. Furthermore, we demonstrate that the C-subregions are key for promoting longitudinal fibre growth. Together, these findings highlight critical functions of the C-subregions in relation to clot structure and stability, with future implications for development of novel therapeutics for thrombosis.

physiology↗

bioRxiv2020

Characterization of cyanobacteria isolated from thermal muds of Balaruc-Les-Bains (France) and description of a new genus and species Pseudochroococcuscouteii

Cyanobacteria are able to synthesize a high diversity of natural compounds that account for their success in the colonization of a variety of ecological niches. Many of them have beneficial properties. The mud from the thermal baths of Balaruc-Les-Bains, one of the oldest thermal baths in France, has long been recognized as a healing treatment for arthro-rheumatic diseases. To characterize the cyanobacteria living in these muds and the metabolites they potentially produce, several strains were isolated from the water column and biofilms of the retention basin and analyzed using a polyphasic approach. Morphological, ultrastructural and molecular (16S rRNA gene and 16S-23S ITS region sequencing) methods were employed to identify nine cyanobacterial strains belonging to the orders Chroococcales, Synechococcales, Oscillatoriales and Nostocales. The combination of morphological and genetic characteristics supported the description of a new genus and species with the type species as Pseudo-chroococcus couteii. The high taxonomic diversity in the muds of the thermal baths of Balaruc-Les-Bains along with literature reports of the potential for bioactive metabolite synthesis of these taxa allowed us to hypothesize that some of the metabolites produced by these strains could contribute to the therapeutic properties of the muds from Thermes de Balaruc-Les-Bains.

microbiology↗