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Cette étude préliminaire porte sur la comparaison des flores diatomiques fossiles et actuelles du lac d’Issarlès (commune Le Lac-d’Issarlès, Ardèche) et de son bassin versant. La flore fossile est étudiée dans une carotte sédimentaire de 1,7 m (partie supérieure d’une carotte de 7 m de long prélevée sous 108 m d’eau), extraite en 2020. La flore actuelle est étudiée dans le lac d’Issarlès ainsi que dans divers points du bassin versant du lac : le ruisseau de la Clède et celui du Ravin des Charbonneyres ainsi que les lacs de barrages du Gage et de la Veyradeyre. La tendance observée de bas en haut de la séquence sédimentaire est marquée par la disparition du genre dominant, Pantocsekiella, remplacé par de nouvelles espèces comme Fragilaria crotonensis et Asterionella formosa qui sont favorisées dans les milieux turbulents et riches en nutriments. Ce bouleversement de la flore est corrélé à l’influence des retenues d’eau connectées au lac d’Issarlès, pièce maîtresse du complexe hydroélectrique de Montpezat mis en service en 1954. Un début d’eutrophisation (augmentation des nutriments et de la matière organique fermentescible) est observé dans le lac actuel. L’étude des diatomées des lacs de barrages et des ruisseaux affluents du lac nous permet de supposer une source d’eutrophisation en provenance du bassin versant naturel du lac, mais également du bassin versant étendu et artificialisé par la mise en place du « complexe hydroélectrique de Montpezat ». La similarité chimique observée entre l’eau du lac et l’eau des retenues souligne la potentielle influence de ces dernières sur la qualité des eaux du lac d’Issarlès. Les données de cette étude préliminaire montrent, d’une part, l’impact de l’exploitation de l’aménagement hydroélectrique de Montpezat sur le lac d’Issarlès et, d’autre part, soulignent une potentielle source de pollution dans le bassin versant du lac, à prendre en compte lors de l’élaboration de futurs plans de gestion. Cette étude livre également des données préliminaires sur l’histoire environnementale récente du lac d’Issarlès, jusqu’à ce jour très peu étudiée.

La source de la Poix est une particularité géologique du Massif central français car elle est connue pour être bitumineuse associée à de l’eau salée, du méthane et des traces d’hydrogène sulfuré. Entre mars 2017 et juin 2020, trois prélèvements ont été effectués en raclant les diatomées sur la couche de bitume. De plus, les conditions physiques et chimiques ont été examinées. Il apparaît que la conductivité de l’eau salée est supérieure à celle de l’océan, entraînant le développement de certaines espèces de diatomées saumâtres, observées pour certaines d’entre elles sur les sédiments intertidaux ou dans les estuaires. Même si les conditions abiotiques étaient extrêmes pour ces algues, la biodiversité était élevée et révèle des espèces ayant une grande capacité à supporter des concentrations et des fluctuations de salinité élevées.

International audience; Light and scanning electron microscope observations on the genus Fontina gen. nov. from a thermo-mineral spring of the Massif Central (France) are presented. Based on morphology, the new genus shows features that have not been described previously, such as the stria pattern, interrupted at the valve face/mantle junction and composed of one long, slit-like areola on both valve face and mantle. Externally, areolae are closed by hymenes. Fontina arverna sp. nov. is described as the typus generis of Fontina. This new genus was compared with some similar freshwater genera such as Adlafia, Chamaepinnularia, Genkalia, Germainiella, Microfissurata and Nupela. So far, we are unable to establish an evolutionary link or cladistic association with currently known genera. The new genus is described from a sampling site characterized by high conductivity and high carbonate concentration, brackish conditions and whose water originates deep in the crust (high lithium concentration).

International audience; Although a strong link between viruses and prokaryotes is commonly known to exist in aquatic systems, few studies have investigated their relationship in spring waters. In the French Massif Central, certain springs are known to exhibit varying levels of naturally occurring radioactivity. Therefore, the aim of this study was to examine the standing stock of viruses together with prokaryotes, and determine the potential environmental factors influencing them in springs characterized by contrasted radioactivity gradient. Among the investigated 15 spring habitats, flow cytometry analyses indicated that both viral (VA) and prokaryotic abundances (PA) varied by an order of magnitude accompanied by virus-to-prokaryote ratio ranging between 8 and 144.2. Significant differences in VA was evident among springs where low abundances (mean ± SD: 21.3 ± 7.0 x 107 VLP l-1) corresponded to high (mean ± SD: 1911 ± 814.0 nGy.h-1) gamma (γ) dose radiation (222Rn) and vice versa. Adverse effect of water radioactivity (222Rn) on VA could perhaps corroborate our hypothesis of drastic effect of ionizing radiations on viruses, which might explain for lack of significant relationship between PA and VA. In such a scenario of prevailing low VA, the adopted phage life strategies could define their existence in these specialized ecosystems.

International audience; Little is still known about the low dose effects of radiation on the microbial communities in the environment. Mineral springs are ecosystems than can be affected by natural radioactivity. These extreme environments are, therefore, observatories for studying the influence of chronic radioactivity on the natural biota. In these ecosystems we find diatoms, unicellular microalgae, playing an essential role in the food chain. The present study aimed to investigate, using DNA metabarcoding, the effect of natural radioactivity in two environmental compartments (i.e. spring sediments and water) on the genetic richness, diversity and structure of diatom communities in 16 mineral springs in the Massif Central, France. Diatom biofilms were collected during October 2019, and a 312 bp region of the chloroplast gene rbcL (coding for the Ribulose Bisphosphate Carboxylase) used as a barcode for taxonomic assignation. A total of 565 amplicon sequence variants (ASV) were found. The dominant ASV were associated with Navicula sanctamargaritae, Gedaniella sp., Planothidium frequentissimum, Navicula veneta, Diploneis vacillans, Amphora copulata, Pinnularia brebissonii, Halamphora coffeaeformis, Gomphonema saprophilum, and Nitzschia vitrea, but some of the ASVs could not be assigned at the species level. Pearson correlation failed to show a correlation between ASV’ richness and radioactivity parameters. Non-parametric MANOVA analysis based on ASVs occurrence or abundances revealed that geographical location was the main factor influencing ASVs distribution. Interestingly, 238U was the second factor that explained diatom ASV structure. Among the ASVs in the mineral springs monitored, ASV associated with one of the genetic variants of Planothidium frequentissimum was well represented in the springs and with higher levels of 238U, suggesting its high tolerance to this particular radionuclide. This diatom species may therefore represent a bio-indicator of high natural levels of uranium

River ecosystems are spatiotemporally and intimately tied to physicochemical and biological processes, driven by strong feedbacks between riparian vegetation dynamics and hydrogeomorphic processes and fluvial landforms. Climatic and hydrogeomorphic constraints to vegetation determine a naturally shifting habitat mosaic dynamism, fostering high habitat heterogeneity and biodiversity, and providing multiple ecosystem services to society. However, most European river systems have lost their inherent highly dynamic character after major human-induced impacts, such as river channelisation and altered flow and sediment regimes. In March 2019, the United Nations designated the period of 2021–2030 as the "Decade on Ecosystem Restoration", and river ecosystems will be a significant target. Consequently, river restoration practitioners will need robust decision-making tools to guide their deliberations and subsequent management actions. Recommendations are to avoid merely reproducing river features and instead restoring geomorphic, hydrological, and ecological processes, but river science has not fully understood yet how processes develop and interact following restoration interventions. Integrative modelling of feedback mechanisms between riparian vegetation dynamics and hydrogeomorphic processes is critical for making predictions that enable river managers to optimise the use of the natural self-regulation potential of riparian corridors whilst maximising human benefits. Today’s existing models, however, do not fully reflect the interactions between river hydraulics and vegetation succession. In particular, the role of vegetation needs to be included through its impact in modulating river landforms and their evolutionary trajectories. Here, we present the conceptual and methodological framework, preliminary results, and the perspectives of the NUMRIP project, funded by the French National Research Agency. Along the project, a numerical (cellular automata) model of fluvial landscape dynamics will be developed, integrating physical, biological, and human components. The project focuses on riparian vegetation, from individual plants to communities. It explicitly considers vegetation as a dynamic component of the system, both responding to and affecting hydrogeomorphic processes and fluvial landforms. Accordingly, NUMRIP builds upon the conceptual fluvial biogeomorphological succession model and recent advances in remote sensing techniques of plant-geomorphology interactions. The NUMRIP project will explicitly associate plant functional traits (e.g., physiological, morphological, and biomechanical characteristics) to hydrogeomorphic processes and fluvial landforms, using plant functional trait approaches, remote sensing- and numerical modelling techniques. The lower course of the Allier River (France) is used as a case study. It is one of the last remaining free meandering river segments in Europe, and thus, constitutes an opportunity to investigate riparian succession processes of a dynamic, temperate river system. Despite its natural character, it is also experimenting an increase of stability (i.e., a reduction in channel migration and progression/retrogression of vegetation patches), because of a concomitant decrease of high and moderate magnitude floods due to current global climate change. The model could be used as a research tool in river science as well as a decision support system for river managers. It will be able to predict potential future evolutionary trajectories of fluvial corridors, adjusting for example to a changing hydrological regime or river restoration works.

International audience; During a survey done on the mineral springs in the French Massif Central region, a new Chamaepinnularia species (Bacillariophyceae) was found and is hereby described: Chamaepinnularia salina Beauger, C.E.Wetzel, Allain & Ector sp. nov. This new small species, with valves linear with almost parallel margins, is formally described using light and scanning electron microscopy. The central area is rectangular, forming a rather broad fascia and the raphe is straight, filiform located on an elevated sternum. Virgae between striae are developed. The ecological preferences of Chamaepinnularia salina are presented. This species is mainly in mineral springs with Na-K-HCO3 water type.

International audience; Diatoms colonised most aquatic ecosystems on earth from marine to freshwater ones, and also the springs containing a fairly large and poorly known diversity of diatoms. While investigations on the influence of substrates on diatom assemblages in rivers are relatively well documented, few studies have been done for mineral springs. The purpose of this study was to analyse if the type of substrate on which diatoms grow, influences diatom assemblage's ecological metrics (i.e. species richness, diversity and evenness) and diatom composition. During 18 months, two minerals springs of Auvergne (France), La Montagne and Mariol were sampled monthly, both epilithic and epipelic diatom communities. A total of 201 taxa were found. Data analysis showed that location (i.e. environmental variables of a site) explained significantly higher portions of variability of diatom composition than substrate. However, substrate have a role in the species abundances as much as the location.

International audience; The TIRAMISU collaboration gathers expertise from biologists, physicists, radiochemists and geologists within the Zone-Atelier Territoires Uranifères (ZATU) in France to study the response of microorganisms living in naturally radioactive mineral springs. Mineral springs are isolated ecosystems, extremely stable over geological time scales, which display different physicochemical and radiological parameters compared to their surroundings. Water and sediment samples collected in 27 mineral springs of the volcanic Auvergne region (Massif Central, France) have been analyzed for their microbial biodiversity and radionuclide content. Among the microorganisms present, diatoms (a microalgae species), widely used as environmental bioindicators of water quality, have shown to display an exceptional abundance of teratogenic forms in the most radioactive springs studied (radon activity up to 3700 Bq/L). The current work presents a first assessment of the dose received by the diatoms inhabiting naturally radioactive mineral springs. The radiological risk for microorganisms living in freshwater environments was estimated using the ERICA tool. Most of the sampled mineral springs were highly above the risk threshold of 10 mGy/h due to the large concentrations of radium in the sediments (up to 50 Bq/g). The complete radiological data on water and sediments are used as inputs to Monte Carlo simulations at micro- (GATE) and nano- (Geant4-DNA) scale in order to assess the direct and indirect damages on the diatom DNA.

International audience; During an archaeological diagnosis carried out by Inrap in 2013 in the commune of Brézins in Isère, a cremation deposit was discovered. As the plot was not subject to an excavation order, the deposit was removed and excavated on the occasion of the Science Festival in 2014 at the Saint-Romain-en-Gal Museum. The results present the analysis of a secondary burial site dated from the final bronze IIIb. It was accompanied by quality artefacts including a copper alloy razor and a tin-decorated cup.; À l’occasion d’un diagnostic réalisé par l’Inrap en 2013 sur la commune de Brézins en Isère, un dépôt secondaire de crémation en fosse a été mis au jour. La parcelle n’ayant pas fait l’objet d’une prescription de fouille, la fosse a été prélevée et fouillée à l’occasion de la Fête de la science en 2014 au musée de Saint-Romain-en-Gal. Les résultats présentent l’analyse de ce dépôt incomplet, daté du Bronze final IIIb, accompagné d’un matériel de qualité comprenant notamment la présence d’un fragment de rasoir en alliage cuivreux et d’un gobelet décoré à l’étain.

This study investigated and compared the diatom flora from thermo-mineral springs in Auvergne (France) and Sardinia (Italy). Samples were collected from rock/cobbles and fine sediments in 16 springs between January 2015 and March 2017. A total of 207 taxa (59 genera) were found. Multivariate analyses revealed significant differences in species composition and abundance among diatom assemblages both within each geographic region and between Auvergne and Sardinia (global R = 0.516; p = 0.002), suggesting the importance of local and climatic factors in species distribution. Based on abundance and common occurrence in multiple sites, some taxa can be considered more representative of springs in each region: Crenotia thermalis for Auvergne and Lemnicola exigua, Nitzschia amphibia, N. inconspicua and Rhopalodia operculata for Sardinia. pH, conductivity and HCO3− were the most significant environmental variables for diatom assemblages. Our results highlight the high heterogeneity of these spring systems. Future taxonomic insights can be useful to define the identity of some abundant and dominant taxa not identified at the species level in this study. Their identification is a crucial step for a more precise ecological characterization and comparison of these peculiar spring systems.

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OBJECTIVES Open arterial revascularization using venous segments is frequently associated with the development of intimal hyperplasia (IH), leading to severe restenosis and graft failure. The lack of treatment to prevent this pathology is a major problem. Therefore, we generated a new porcine model, which closely mimics the clinical development of human IH, to test the therapeutic potential of candidate drugs. METHODS A patch of jugular vein was sutured to the right common carotid artery of pigs, to expose the vein to haemodynamic conditions of the arterial bed. Four weeks after surgery, the operated vessels which received no further treatment (the control group) were compared with (i) contralateral, non-operated vessels (the healthy group); (ii) vessels of pigs that received a perivascular application of a drug-free microparticle gel (the placebo group) and (iii) vessels of pigs that perioperatively received the same gel loaded with 10-mg atorvastatin (the atorvastatin group). RESULTS When compared with non-operated vessels, all operated segments displayed a sizable IH which was thicker in the venous patch than in the host artery. These alterations were associated with a thickening of the intima layer of both vessels in the absence of inflammation. The intima/media ratio has been significantly increased by 2000-fold in the vein patches. Perivascular application of atorvastatin did not prevent IH formation. However, the drug increased the adventitial neovascularization in the operated vessels. CONCLUSIONS The novel porcine model allows for monitoring IH formation under haemodynamic conditions which mimic clinical situations. It should facilitate the screening of innovative treatments to prevent restenosis.

International audience; Signaling of chromosomal DNA breaks is of primary importance for initiation of repair and, thus, for global genomic stability. Although the Mre11-Rad50-Nbs1 (MRN) complex is the first sensor of double-strand breaks, its role in double-strand break (DSB) signaling is not fully understood. We report the absence of γ-ray-induced, ATM/ATR-dependent histone H2AX phosphorylation in Arabidopsis thaliana rad50 and mre11 mutants, confirming that the MRN complex is required for H2AX phosphorylation by the ATM and ATR kinases in response to irradiation-induced DSB in Arabidopsis. rad50 and mre11 mutants spontaneously activate a DNA damage response, as shown by the presence of γ-H2AX foci and activation of cell cycle arrest in nonirradiated plants. This response is ATR dependent as shown both by the absence of these spontaneous foci and by the wild-type mitotic indices of double rad50 atr and mre11 atr plants. EdU S-phase labeling and fluorescence in situ hybridization analysis using specific subtelomeric probes point to a replicative S-phase origin of this chromosome damage in the double mutants and not to telomere destabilization. Thus, the data presented here show the exclusive involvement of ATR in DNA damage signaling in MRN mutants and provide evidence for a role for ATR in the avoidance of S-phase DNA damage.

International audience; The telomeres of linear eukaryotic chromosomes are protected by caps consisting of evolutionarily conserved nucleoprotein complexes. Telomere dysfunction leads to recombination of chromosome ends and this can result in fusions which initiate chromosomal breakage-fusion-bridge cycles, causing genomic instability and potentially cell death or cancer. We hypothesize that in the absence of the recombination pathways implicated in these fusions, deprotected chromosome ends will instead be eroded by nucleases, also leading to the loss of genes and cell death. In this work, we set out to specifically test this hypothesis in the plant, Arabidopsis. Telomere protection in Arabidopsis implicates KU and CST and their absence leads to chromosome fusions, severe genomic instability and dramatic developmental defects. We have analysed the involvement of end-joining recombination pathways in telomere fusions and the consequences of this on genomic instability and growth. Strikingly, the absence of the multiple end-joining pathways eliminates chromosome fusion and restores normal growth and development to cst ku80 mutant plants. It is thus the chromosomal fusions, per se, which are the underlying cause of the severe developmental defects. This rescue is mediated by telomerase-dependent telomere extension, revealing a competition between telomerase and end-joining recombination proteins for access to deprotected telomeres.

INTRODUCTION:Popliteal artery aneurysm (PAA) is the most common peripheral arterial aneurysm and the second most common aneurysm after abdominal aortic aneurysm (AAA). It presents a risk of occlusion, which may lead to acute ischemia and leg amputation. To prevent these risks, asymptomatic PAA >2cm and symptomatic PAA must be treated. Although open PPA repair (OPAR) is still the gold standard, endovascular PAA repair (EPAR) is increasingly used to manage PAA. The objective of this study is to compare the cost of these two medical procedures from the hospital perspective.METHODS:Data were retrieved from the administrative database of Lausanne University Hospital (CHUV – Switzerland). Based on diagnostic codes and medical procedure codes, we selected all patients who underwent OPAR or EPAR between 2011 and 2015. Patient's age, length of stay and cost were compared between both groups using Student t-test.RESULTS:We included seventy-three patient stays (OPAR forty and EPAR thirty-three). Gender balance was identical between groups (97 percent of male), but age was statistically significantly different (OPAR 67.5, EPAR 73, p = .04). EPAR induced shorter mean length of stay (5.1 days versus 11.7 days, p = .0000) and lower mean global cost (CHF 16,555 versus CHF23,514, p = .0085). Cost of procedure amounted to CHF 9,536 for OPAR versus CHF 3,848 for EPAR, medical supply and implants amounted to CHF 1,284 for OPAR versus CHF 7,041 for EPAR and other costs of hospital stay amounted to CHF 12,694 for OPAR versus CHF 5,666 for EPAR. (CHF 1.00 = USD1.00 = EURO 0.93)CONCLUSIONS:With higher patency rate, OPAR is still associated with better medical outcomes than EPAR. But EPAR is significantly less costly than OPAR. Implant cost of EPAR is more than offset by longer length of stay and operating time of OPAR.

The ends of linear eukaryotic chromosomes are hidden in nucleoprotein structures called telomeres, and loss of the telomere structure causes inappropriate repair, leading to severe karyotypic and genomic instability. Although it has been shown that DNA damaging agents activate a DNA damage response (DDR), little is known about the signaling of dysfunctional plant telomeres. We show that absence of telomerase in Arabidopsis thaliana elicits an ATAXIA-TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR)-dependent DDR at telomeres, principally through ATM. By contrast, telomere dysfunction induces an ATR-dependent response in telomeric Conserved telomere maintenance component1 (Ctc1)-Suppressor of cdc thirteen (Stn1)-Telomeric pathways in association with Stn1 (CST)–complex mutants. These results uncover a new role for the CST complex in repressing the ATR-dependent DDR pathway in plant cells and show that plant cells use two different DNA damage surveillance pathways to signal telomere dysfunction. The absence of either ATM or ATR in ctc1 and stn1 mutants significantly enhances developmental and genome instability while reducing stem cell death. These data thus give a clear illustration of the action of ATM/ATR-dependent programmed cell death in maintaining genomic integrity through elimination of genetically unstable cells.

International audience; Double-strand breaks in genomic DNA (DSB) are potentially lethal lesions which separate parts of chromosome arms from their centromeres. Repair of DSB by recombination can generate mutations and further chromosomal rearrangements, making the regulation of recombination and the choice of recombination pathways of the highest importance. Although knowledge of recombination mechanisms has considerably advanced, the complex interrelationships and regulation of pathways are far from being fully understood. We analyse the different pathways of DSB repair acting in G2/M phase nuclei of irradiated plants, through quantitation of the kinetics of appearance and loss of γ-H2AX foci in Arabidopsis mutants. These analyses show the roles for the four major recombination pathways in post-S-phase DSB repair and that non-homologous recombination pathways constitute the major response. The data suggest a hierarchical organisation of DSB repair in these cells: C-NHEJ acts prior to B-NHEJ which can also inhibit MMEJ. Surprisingly the quadruple ku80 xrcc1 xrcc2 xpf mutant can repair DSB, although with severely altered kinetics. This repair leads to massive genetic instability with more than 50% of mitoses showing anaphase bridges following irradiation. This study thus clarifies the relationships between the different pathways of DSB repair in the living plant and points to the existence of novel DSB repair processes.

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