Microbial education plays a crucial role in harnessing the beneficial properties of microbiota for infectious disease protection in Crassostrea gigas.

The increase in marine diseases, particularly in economically important mollusks, is a growing concern. Among them, the Pacific oyster (Crassostrea gigas) production faces challenges from several diseases, such as the Pacific Oyster Mortality Syndrome (POMS) or vibriosis. The microbial education, which consists of exposing the host immune system to beneficial microorganisms during early life stages is a promising approach against diseases.

Cross-talk and mutual shaping between the immune system and the microbiota during an oyster's life.

The Pacific oyster lives in microbe-rich marine coastal systems subjected to rapid environmental changes. It harbours a diversified and fluctuating microbiota that cohabits with immune cells expressing a diversified immune gene repertoire. In the early stages of oyster development, just after fertilization, the microbiota plays a key role in educating the immune system.

Impact of epizootics on mussel farms: Insights into microbiota composition of Mytilus species.

Outbreaks of marine mussel mortality on French farms could have different aetiologies. One of them implies Vibrio splendidus strains. Beyond the involvement of this pathogen, there is considerable evidence that diseases often result from interactions between several microbes and the host.

Functional Diversification of Oyster Big Defensins Generates Antimicrobial Specificity and Synergy against Members of the Microbiota.

Big defensins are two-domain antimicrobial peptides (AMPs) that have highly diversified in mollusks. -BigDefs are expressed by immune cells in the oyster , and their expression is dampened during the Pacific Oyster Mortality Syndrome (POMS), which evolves toward fatal bacteremia. We evaluated whether -BigDefs contribute to the control of oyster-associated microbial communities.

Vibrio splendidus infection induces dysbiosis in the blue mussel and favors pathobiontic bacteria.

Studies on marine epizootics are often based on the identification of a single pathogen. However, the one-pathogen-one-disease paradigm is not always sufficient to explain the disease, especially since the evidences on the role of microbiota in health and disease. Vibrio splendidus strains have been associated with Mytilus edulis mortality in France.

Tetrodotoxins in French Bivalve Mollusks-Analytical Methodology, Environmental Dynamics and Screening of Bacterial Strain Collections.

Tetrodotoxins (TTXs) are potentially lethal paralytic toxins that have been identified in European shellfish over recent years. Risk assessment has suggested comparatively low levels (44 µg TTX-equivalent/kg) but stresses the lack of data on occurrence. Both bacteria and dinoflagellates were suggested as possible biogenic sources, either from an endogenous or exogenous origin.

Susceptibility variation to the main pathogens of Crassostrea gigas at the larval, spat and juvenile stages using unselected and selected oysters to OsHV-1 and/or V. aestuarianus.

French commercial hatcheries are massively producing Crassostrea gigas selected for their higher resistance to OsHV-1, and soon should also implement selection for increasing resistance to Vibrio aestuarianus. The first objective of this study was to optimize the breeding programs for dual resistance to OsHV-1 and V. aestuarianus to determine the earliest life stage for which oysters are able to develop disease resistance.

subsp. subsp. nov., pathogenic to the edible cockles in France, and establishment of subsp. subsp. nov. and subsp. subsp. nov.

Cockle mortality events have been reported in northern France since 2012. In the present study, we describe and investigate the implication of a potential bacterial causative agent in cockle mortality. Bacteria isolated from five different cockle mortality events were characterized and studied.

Vibrio-bivalve interactions in health and disease.

In the marine environment, bivalve mollusks constitute habitats for bacteria of the Vibrionaceae family. Vibrios belong to the microbiota of healthy oysters and mussels, which have the ability to concentrate bacteria in their tissues and body fluids, including the hemolymph. Remarkably, these important aquaculture species respond differently to infectious diseases.

Modeling the Transmission of in Pacific Oysters Using Experimental Infection Data.

is a bacterium related to mortality outbreaks in Pacific oysters, , in France, Ireland, and Scotland since 2011. Knowledge about its transmission dynamics is still lacking, impairing guidance to prevent and control the related disease spread. Mathematical modeling is a relevant approach to better understand the determinants of a disease and predict its dynamics in imperfectly observed pathosystems.

A study of autophagy in hemocytes of the Pacific oyster, .

Macroautophagy is a mechanism that is involved in various cellular processes, including cellular homeostasis and innate immunity. This pathway has been described in organisms ranging in complexity from yeasts to mammals, and recent results indicate that it occurs in the mantle of the Pacific oyster, . However, the autophagy pathway has never been explored in the hemocytes of , which are the main effectors of its immune system and thus play a key role in the defence of the Pacific oyster against pathogens.

Complex Relationships between the Blue Pigment Marennine and Marine Bacteria of the Genus .

Marennine, the water-soluble blue pigment produced by the marine diatom , is known to display antibacterial activities. Previous studies have demonstrated a prophylactic effect of marennine on bivalve larvae challenged with a pathogenic , suggesting that the blue is a good candidate for applications in aquaculture as a source of a natural antimicrobial agent. Indeed, the genus is ubiquitous in aquaculture ecosystems, and regular events of pathogenic invasion cause some of the biggest losses worldwide.

Oyster Farming, Temperature, and Plankton Influence the Dynamics of Pathogenic Vibrios in the Thau Lagoon.

species have been associated with recurrent mass mortalities of juvenile oysters threatening oyster farming worldwide. However, knowledge of the ecology of pathogens in affected oyster farming areas remains scarce. Specifically, there are no data regarding (i) the environmental reservoirs of populations pathogenic to oysters, (ii) the environmental factors favoring their transmission, and (iii) the influence of oyster farming on the persistence of those pathogens.

Ecologically realistic model of infection for exploring the host damage caused by Vibrio aestuarianus.

Although vibrios are frequently associated with marine organisms mortality outbreaks, knowledge on their ecology and pathogenicity is sparse, thus limiting disease management and prophylactic strategies. Here, we investigated V. aestuarianus infection onset and progression in the wild, taking advantage of a 'claire' pond: a semi-closed system with limited seawater renewal, theoretically more adapted to disease transmission.

Bile Salt Hydrolase Activities: A Novel Target to Screen Anti- Lactobacilli?

is a protozoan parasite responsible for giardiasis, a disease characterized by intestinal malabsorption, diarrhea and abdominal pain in a large number of mammal species. Giardiasis is one of the most common intestinal parasitic diseases in the world and thus a high veterinary, and public health concern. It is well-established that some probiotic bacteria may confer protection against this parasite and and we recently documented the implication of bile-salt hydrolase (BSH)-like activities from strain La1 of as mediators of these effects .

Infection dynamics of a V. splendidus strain pathogenic to Mytilus edulis: In vivo and in vitro interactions with hemocytes.

The pathogenic strain V. splendidus 10/068 1T1 has previously been reported for its virulence to the blue mussel and for its capacity to alter immune responses. In this study, we expanded the knowledge on hemocyte-pathogen interactions by using in vitro and in vivo assays.

Development of a duplex Taqman real-time PCR assay for rapid identification of Vibrio splendidus-related and V. aestuarianus strains from bacterial cultures.

To enable the rapid and accurate identification of Vibrio splendidus-related and V. aestuarianus strains associated with Pacific cupped oyster Crassostrea gigas mortality, we developed a duplex Taqman real-time PCR assay and evaluated its efficacy. This technique proved to be rapid, sensitive, and specific and will be particularly valuable for epidemiologic studies.

Several strains, one disease: experimental investigation of Vibrio aestuarianus infection parameters in the Pacific oyster, Crassostrea gigas.

This study investigated oyster infection dynamics by different strains of Vibrio aestuarianus isolated before and after the apparent re-emergence of this pathogen observed in France in 2011. We conducted experiments to compare minimal infective dose, lethal dose 50 and bacterial shedding for six V. aestuarianus strains.

Deconjugated Bile Salts Produced by Extracellular Bile-Salt Hydrolase-Like Activities from the Probiotic La1 Inhibit Growth.

Giardiasis, currently considered a neglected disease, is caused by the intestinal protozoan parasite and is widely spread in human as well as domestic and wild animals. The lack of appropriate medications and the spread of resistant parasite strains urgently call for the development of novel therapeutic strategies. Host microbiota or certain probiotic strains have the capacity to provide some protection against giardiasis.