Biology subjects

Travers, M.-A.

Publications and source records attributed to Travers, M.-A..

3 recordsLinked to original sources

bioRxiv2024

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

BackgroundRecently, the frequency and severity of marine diseases have increased in association with global changes, and molluscs of economic interest are particularly concerned. Among them, the Pacific oyster (Crassostrea gigas) production faces challenges from several diseases such as the Pacific Oyster Mortality Syndrome (POMS) or vibriosis. Various strategies such as genetic selection or immune priming have been developed to fight some of these infectious diseases. The microbial education, which consist of exposing the host immune system to beneficial microorganisms during early life stages is a promising approach against diseases. This study explores the concept of microbial education using controlled and pathogen-free bacterial communities and assesses its protective effects against POMS and Vibrio aestuarianus infections, highlighting potential applications in oyster production. ResultsWe demonstrate that it is possible to educate the oyster immune system by adding microorganisms during the larval stage. Adding culture based bacterial mixes to larvae protects only against the POMS disease while adding whole microbial communities from oyster donors protects against both POMS and vibriosis. The efficiency of the immune protection depends both on oyster origin and on the composition of the bacterial mixes used for exposure. No preferential protection was observed when the oysters were stimulated with their sympatric strains. We further show that the added bacteria were not maintained in the oyster microbiota after the exposure, but this bacterial addition induced long term changes in the microbiota composition and oyster immune gene expression. ConclusionOur study reveals successful immune system education of oysters by introducing beneficial micro-organisms during the larval stage. We improved the long-term resistance of oysters against critical diseases (POMS disease and Vibrio aestuarianus infections) highlighting the potential of microbial education in aquaculture.

microbiology↗

bioRxiv2023

Cooperation and cheating orchestrate Vibrio assemblages and polymicrobial synergy in oysters infected with OsHV-1 virus

Polymicrobial diseases significantly impact the health of humans and animals but remain understudied in natural systems. We recently described the Pacific Oyster Mortality Syndrome (POMS), a polymicrobial disease that impacts oyster production and is prevalent worldwide. Analysis of POMS-infected oysters on the French North Atlantic coast revealed that the disease involves co-infection with the endemic ostreid herpesvirus 1 (OsHV-1) and virulent bacterial species such as Vibrio crassostreae. However, it is unknown whether consistent Vibrio populations are associated with POMS in different regions, how Vibrio contribute to POMS, and how they interact with the OsHV-1 virus during pathogenesis. We resolved the Vibrio population structure in oysters from a Mediterranean ecosystem and investigated their functions in POMS development. We find that Vibrio harveyi and Vibrio rotiferianus are the predominant species found in OsHV-1-diseased oysters and show that OsHV-1 is necessary to reproduce the partition of the Vibrio community observed in the field. By characterizing the interspecific interactions between OsHV-1, V. harveyi and V. rotiferianus, we find that only V. harveyi synergizes with OsHV-1. When co-infected, OsHV-1 and V. harveyi behave cooperatively by promoting mutual growth and accelerating oyster death. V. harveyi showed high virulence potential in oysters and dampened host cellular defenses, making oysters a more favorable niche for microbe colonization. We next investigated the interactions underlying the co-occurrence of diverse Vibrio species in diseased oysters. We found that V. harveyi harbors genes responsible for the biosynthesis and uptake of a key siderophore called vibrioferrin. This important resource promotes the growth of V. rotiferianus, a cheater that efficiently colonizes oysters during POMS without costly investment in host manipulation nor metabolite sharing. By connecting field-based approaches, laboratory infection assays and functional genomics, we have uncovered a web of interdependencies that shape the structure and function of the POMS pathobiota. We showed that cooperative behaviors contribute to synergy between bacterial and viral co-infecting partners. Additional cheating behaviors further shape the polymicrobial consortium. Controlling such behaviors or countering their effects opens new avenues for mitigating polymicrobial diseases.

microbiology↗

bioRxiv2022

Emergence and clonal expansion in Europe of Vibrio aestuarianus lineages pathogenic for oysters

Crassostrea gigas oysters represent a significant global food source, with 4.7 million tons harvested per year. In 2001, the bacterium V. aesturianus francensis emerged as a pathogen that causes adult oyster mortality in France and Ireland. Its impact on oyster aquaculture has increased in Europe since its reemergence in 2012. To better understand the evolutionary mechanisms leading to the emergence and persistence over time of this pathogen, we conducted a survey of mollusk diseases through national reference laboratories (NRLs) across Europe. We analyzed 54 new genomes of V. aestuarianus (Va) isolated from multiple environmental compartments since 2001, in areas with and without bivalve mortalities. We used a combination of comparative genomics and population genetics approaches to show that Va francensis lineages have undergone clonal expansion in Europe, likely after a recent selective bottleneck. Low mutation and recombination rates may have selected particular virulent genotypes. Furthermore, we identified a specific cus-cop-containing island conferring copper resistance to Va francensis whose acquisition may have favored the emergence of pathogenic lineages adapted to oysters.

microbiology↗