The Effect of Captivity on the Dynamics of Active Bacterial Communities Differs Between Two Deep-Sea Coral Species

Microbes play a crucial role in sustaining the coral holobiont’s functions and in particular under the pressure of environmental stressors. The effect of a changing environment on coral health is now a major branch of research that relies heavily on aquarium experiments. However, the effect of captivity on the coral microbiome remains poorly known. Here we show that different cold-water corals species have different microbiome responses to captivity. For both the DNA and the RNA fraction, Madrepora oculata bacterial communities were maintained for at least 6 months of aquarium rearing, while Lophelia pertusa bacteria changed within a day. Interestingly, bacteria from the genus Endozoicomonas, a ubiquitous symbiont of numerous marine hosts, were resilient and remained active in M. oculata for several months. Our results demonstrate that a good knowledge of the coral microbiome and an understanding of the ecological strategy of the holobiont is needed before designing aquarium experiments

Microbial Ecotoxicology of Marine Plastic Debris: A Review on Colonization and Biodegradation by the “Plastisphere”

Over the last decades, it has become clear that plastic pollution presents a global societal and environmental challenge given its increasing presence in the oceans. A growing literature has focused on the microbial life growing on the surfaces of these pollutants called the “plastisphere,” but the general concepts of microbial ecotoxicology have only rarely been integrated. Microbial ecotoxicology deals with (i) the impact of pollutants on microbial communities and inversely (ii) how much microbes can influence their biodegradation. The goal of this review is to enlighten the growing literature of the last 15 years on microbial ecotoxicology related to plastic pollution in the oceans. First, we focus on the impact of plastic on marine microbial life and on the various functions it ensures in the ecosystems. In this part, we also discuss the driving factors influencing biofilm development on plastic surfaces and the potential role of plastic debris as vector for dispersal of harmful pathogen species. Second, we give a critical view of the extent to which marine microorganisms can participate in the decomposition of plastic in the oceans and of the relevance of current standard tests for plastic biodegradability at sea. We highlight some examples of metabolic pathways of polymer biodegradation. We conclude with several questions regarding gaps in current knowledge of plastic biodegradation by marine microorganisms and the identification of possible directions for future research

Reproductive cycle and temperature-related differences in baseline levels of HSP70 and metallothioneins in wild oyster populations of Crassostrea gigas

International audienceHeat Shock Protein 70 (HSP70) are generalist stress proteins expressed in response to numerous environmental stresses. However, the baselines of these constitutive proteins are still unknown in many organisms and in particular marine intertidal species such as the Pacific oyster, Crassostrea gigas. I demonstrate that levels of heat shock proteins (HSP) and other stress proteins (metallothioneins, MTs) quantified by ELISA, remained similar in gills, mantle and digestive gland between oysters inhabiting cold and hot sites. In contrast, endogenous HSPs and MTs levels in gonad changed significantly during gametogenesis. In female gonads, the constitutive form of HSP70 and the MTs increased from immature to mature stages (about more than 3-fold) and decreased after spawning. In male gonads, the same expression patterns were observed, whereas protein levels were lower and decreased once fully mature. I hypothesize that the high level of stress proteins in eggs may increase survival of oyster progen

Capacité d'adaptation d'une espèce invasive, l'huître creuse du Pacifique Crassostrea gigas, en région Bretagne

L huître creuse du Pacifique Crassostrea gigas est une espèce d intérêt économique en France. L extension de cette espèce pendant le dernier siècle a rapidement conduit au développement de populations sauvages. C. gigas est, à présent, considérée comme une espèce invasive dans de nombreuses régions du globe. L objectif principal de ce travail est de comprendre les capacités adaptatives de cette espèce, à l aide d une approche génétique et physiologique à différentes échelles spatiales et temporelles. A macro-échelle (le long des côtes françaises) et à micro-échelle (bas et haut d estran), une différenciation génétique significative a été observée entre les population adultes à l aide de marqueurs exoniques et allozymiques. A contrario, cette différence n a pas décelée par les microsatellites. Dans trois sites bretons, une structuration génétique significative a été observée entre les adultes et les jeunes recrues des années 2005 et 2006, e également entre ces recrues et des naissains cultivés. Dans la seconde partie de cette étude, plusieurs indicateurs physiologiques de santé et de la fitness ont été estimés sur des adultes des trois sites cités précédemment. De fortes différences significatives ont été observées entre des individus de sexe et de stade de gamétogenèse différent, au cours de l année 2005. Cependant, aucune différence majeure des performances physiologiques n a été révélée entre les adultes à micro- et macro-échelles spatiales. En conclusion, l ensemble de ces résultats suggère un fort potentiel invasif de C. gigas, résultant d une plasticité phénotypique et surtout d une sélection locale appliquée sur sa forte diversité génétique.The Pacific oyster Crassostrea gigas is an important commercial species in France. The wide distribution of this species during the last decade quickly led to the developmeht of wild populations mainly in rocky intertidal areas. C. gigas is now considered an invasive species in various parts of the world. The main objective of this work was to characterize the adaptative capabilities of C. giqas in Brittany using genetic and physiological approaches at different spatial and temporal scales. Using exonic markers, significant genetic structures were observed between populations of adult oysters along the French coasts. In contrast, this difference was not observed using microsatellites. The study at the micro-scale, demonstrated no significant difference in allelic frequencies between oysters at high and low tidal heights, except at the MPI locus via allozymes analysis. At three sites f rom Brittany, significant genetic structure was observed between adult and juvenile oysters recruited in 2005 and 2006 and also between these same juveniles and cultivated spat. In the second part of this study, several physiological indicators of health and fitness-related traits were assessed on adults from the three sites described above. Strong significant differences were found between sex and gametogenesis stages throughout the year 2005. In contras no differential physiological performance was illustrated between adults at macro and micro-spatial scales. In conclusion, aIl of these results suggest a high potential of invasion for as that correspond to the compound of phenotypic plasticity and all above local selection applied to its high genetic diversity.BREST-BU Droit-Sciences-Sports (290192103) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

Pathobiomes Differ between Two Diseases Affecting Reef Building Coralline Algae

Crustose coralline algae (CCA) are major benthic calcifiers that play crucial roles in coral reef ecosystems. Two diseases affecting CCA have recently been investigated: coralline white band syndrome (CWBS) and coralline white patch disease (CWPD). These diseases can trigger major losses in CCA cover on tropical coral reefs, but their causative agents remain unknown. Here, we provide data from the first investigation of the bacterial communities associated with healthy and diseased CCA tissues. We show that Neogoniolithon mamillare diseased tissues had distinct microbial communities compared to healthy tissues and demonstrate that CWBS and CWPD were associated with different pathobiomes, indicating that they had different disease causations. CWBS tissues were composed of opportunistic bacteria, and the origin of the disease was undetermined. In contrast, a vibrio related to Vibrio tubiashii characterized the CWPD pathobiome, suggesting that it could be a putative disease agent and supporting the case of a temperature dependent disease associated with global warming

High-Resolution Melting of 18S rDNA sequences (18S-HRM) for discrimination of bivalve’s species at early juvenile stage: application to a spat survey

International audienceIt is particularly difficult to identify bivalve species at early development stages (larvae and spat) by morphological examination. Targeting genetic marker commonly used for species identification, we developed a cheap and user friendly tool for bivalve identification through High-Resolution Melting (HRM) analysis. Based on the polymorphism of the nuclear 18S ribosomal RNA gene among 11 orders of bivalve, the 18S-HRM method allowed discriminating species of the Ostreida, Mytilida and Pectinida orders. In this study, this method proved to be a very sensitive tool able to authenticate one species that differed by only one mutation from another one. We applied the method by identifying bivalve species in spat collections from different benthic substrates moored at subtidal and intertidal areas in euhaline conditions. This field survey showed that the settlement of the invasive species Crassostrea gigas was limited vertically to intertidal substrates. In conclusion, the 18S-HRM analysis is a fast, closed-tube method with high resolution and cost effectiveness, and is thus a good alternative method to identify bivalve species. This HRM assay can by applied for species identification of bivalves in the context of ecological management as well as food traceability for bivalves with economical interests

Oxidative stress biomarkers in the Mediterranean pond turtle ( Mauremys leprosa ) reveal contrasted aquatic environments in Southern France

International audienceIncreasing anthropogenic activities, like agricultural practices, constitute the main causes of the loss ofwater quality and disruption of freshwater ecosystems. High concentrations of pesticides, as shownunder experimental conditions, can indeed impact freshwater animals. In Southern France, especially inthe Pyrenees-Orientales department, because agricultural activities are mainly based on fruit crops andvineyards, glyphosate and AMPA were detected in some watercourses. Thereby we investigated the effectsof degraded waters on the physiology of the endemic endangered freshwater species, namely theMediterranean pond turtle Mauremys leprosa, in contrasted environments along the same rivers on theone hand and between different rivers on the other. We measured the activity and gene expression oftwo enzymes involved in the oxidative detoxification processes, namely the Catalase and the Superoxidedismutase. We showed significant variations in the Catalase gene expression and activity within turtlesof the Fosseille River depending of their location, i.e. upstream or downstream of the wastewatertreatment plants (WTP). Because agricultural environments are similar all along this river, they can no belonger considered as the unique source of turtle stress. The processed waters discharged by the WTP

The high resolution melting analysis (HRM) as a molecular tool for monitoring parasites of the wildlife

International audienceIn an interconnected world, the international pet trade on wild animals is becoming increasingly important. As a consequence, non-native parasite species are introduced, which affect the health of wildlife and contribute to the loss of biodiversity. Because the investigation of parasite diversity within vulnerable host species implies the molecular identification of large samples of parasite eggs, the sequencing of DNA barcodes is time-consuming and costly. Thereby, the objectives of our study were to apply the high resolution melting (HRM) approach for species determination from pools of parasite eggs. Molecular assays were validated on flatworm parasites (polystomes) infecting the Mediterranean pond turtle Mauremys leprosa and the invasive red-eared slider Trachemys scripta elegans in French natural environments. HRM analysis results indicated that double or multiple parasitic infections could be detected from wild animal populations. They also showed that the cycle of parasite eggs production was not regular over time and may depend on several factors, among which the ecological niche and the target species. Thereby, monitoring parasites from wild endangered animals implies periodic parasitological surveys to avoid false negative diagnostics, based solely on eggs production

Identification of differentially expressed genes of the Pacific oyster Crassostrea gigas exposed to prolonged thermal stress

International audienceGroups of oysters (Crassostrea gigas) were exposed to 25 degrees C for 24 days (controls to 13 degrees C) to explore the biochemical and molecular pathways affected by prolonged thermal stress. This temperature is 4 degrees C above the summer seawater temperature encountered in western Brittany, France where the animals were collected. Suppression subtractive hybridization was used to identify specific up- and downregulated genes in gill and mantle tissues after 7-10 and 24 days of exposure. The resulting libraries contain 858 different sequences that potentially represent highly expressed genes in thermally stressed oysters. Expression of 17 genes identified in these libraries was studied using real-time PCR in gills and mantle at different time points over the course of the thermal stress. Differential gene expression levels were much higher in gills than in the mantle, showing that gills are more sensitive to thermal stress. Expression of most transcripts (mainly heat shock proteins and genes involved in cellular homeostasis) showed a high and rapid increase at 3-7 days of exposure, followed by a decrease at 14 days, and a second, less-pronounced increase at 17-24 days. A slow-down in protein synthesis occurred after 24 days of thermal stress

Pathobiomes Differ between Two Diseases Affecting Reef Building Coralline Algae

International audienceCrustose coralline algae (CCA) are major benthic calcifiers that play crucial roles in coral reef ecosystems. Two diseases affecting CCA have recently been investigated: coralline white band syndrome (CWBS) and coralline white patch disease (CWPD). These diseases can trigger major losses in CCA cover on tropical coral reefs, but their causative agents remain unknown. Here, we provide data from the first investigation of the bacterial communities associated with healthy and diseased CCA tissues. We show that Neogoniolithon mamillare diseased tissues had distinct microbial communities compared to healthy tissues and demonstrate that CWBS and CWPD were associated with different pathobiomes, indicating that they had different disease causations. CWBS tissues were composed of opportunistic bacteria, and the origin of the disease was undetermined. In contrast, a vibrio related to Vibrio tubiashii characterized the CWPD pathobiome, suggesting that it could be a putative disease agent and supporting the case of a temperature dependent disease associated with global warming