Tahiti, French Polynesia
Tahiti, French Polynesia

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Travers M.-A.,French Research Institute for Exploitation of the Sea | Mersni Achour R.,French Research Institute for Exploitation of the Sea | Mersni Achour R.,CNRS Coastal and Marine Environment Laboratory | Mersni Achour R.,University of La Rochelle | And 11 more authors.
Journal of Invertebrate Pathology | Year: 2014

Nine dominant bacterial isolates were obtained from different batches of Crassostrea gigas spat experiencing high mortality rates in a French experimental hatchery/nursery in 2007. Using phenotypic analysis combined with multilocus sequence analysis, the isolates were shown to be genetically close to the Vibrio tubiashii type strain. Based on (1) analyses of the recA gene sequences; (2) the results of DNA-DNA hybridization assays between 07/118 T2 (LMG 27884 = CECT 8426), which is a representative strain, and the V. tubiashii type strain (69%); and (3) phenotypic traits, the bacteria were classified in a group close to American V. tubiashii strain. Its virulence (70% of mortalities) and the toxicity of the extracellular products of 07/118 T2 was demonstrated (41% of mortalities).Moreover, a QPCR diagnostic tool targeting the gyrB gene was developed to investigate the epidemiological significance of V. tubiashii in French oyster mortality outbreaks recorded by the national surveillance network. Of the 21 batches originating from hatcheries, only two were positive, whereas V. tubiashii DNA could not be detected in any of the batches of moribund animals collected in field/outdoor facilities. These results demonstrate the existence of a group of virulent V. tubiashii in France that episodically infect C. gigas. © 2014 Elsevier Inc.

Mersni-Achour R.,CNRS Coastal and Marine Environment Laboratory | Mersni-Achour R.,French Research Institute for Exploitation of the Sea | Mersni-Achour R.,University of La Rochelle | Imbert-Auvray N.,CNRS Coastal and Marine Environment Laboratory | And 11 more authors.
Journal of Invertebrate Pathology | Year: 2014

Extracellular products (ECPs) of the French Vibrio tubiashii strain 07/118 T2 were previously reported to be toxic for the Pacific oyster Crassostrea gigas. In this study we now assessed host cellular immune responses and bacterial potential effectors by which these ECPs can be associated with host damages. The adhesion capacity (28% inhibition) and phagocytosis ability (56% inhibition) of oyster hemocytes were the main functions affected following in vitro contact between hemocytes and V. tubiashii ECPs. This may be linked to the demonstration of the capability of ECPs to cleave various cellular substrates as oyster collagen.Moreover, a strong metalloproteolytic activity was recorded with general (azocasein) and specific (ADAM) substrates and characterized by the use of standard inhibitors and metal ions. The addition of 1,10-phenanthroline and Zn2+ decreased proteolytic activity by about 80% and 50% respectively, confirming the presence of zinc metalloproteolytic activity in the ECPs. Mass spectrometry analyses of crude ECPs identified an extracellular zinc metalloprotease encoded by a gene with an open reading frame of 1821bp (606 aa). Consensus zinc-binding motifs specific to thermolysin family and some glycosylation and phosphorylation sites were located on the deduced protein sequence.Taken together, our results suggest that this (these) zinc metalloprotease(s) might contribute to the impairment of hemocyte immunological functions; however, their direct involvement in ECPs toxicity remains to be demonstrated. © 2014 Elsevier Inc.

PubMed | Center Ifremer du Pacifique, French Research Institute for Exploitation of the Sea, CNRS Coastal and Marine Environment Laboratory and University of Western Brittany
Type: Journal Article | Journal: Microbiology (Reading, England) | Year: 2015

Vibrio tubiashii is a marine pathogen isolated from larval and juvenile bivalve molluscs that causes bacillary necrosis. Recent studies demonstrated the isolation of this species in a French experimental hatchery/nursery affecting Crassostrea gigas spat in 2007. Here, using larvae of C. gigas as an interaction model, we showed that the French V. tubiashii is virulent to larvae and can cause bacillary necrosis symptoms with an LD50 of about 2.3 10(3) c.f.u. ml(-1) after 24 h. Moreover, complete or gel permeation HPLC fractionated extracellular products (ECPs) of this strain appeared toxic to larvae. MS-MS analysis of the different ECP fractions revealed the existence of an extracellular metalloprotease and other suspected virulence factors. This observation is also supported by the expression level of some potential virulence factors. The overall results suggest that the pathology caused by the French V. tubiashii in C. gigas oysters is caused by a group of toxic factors and not only the metalloprotease.

Schikorski D.,French Research Institute for Exploitation of the Sea | Renault T.,French Research Institute for Exploitation of the Sea | Paillard C.,University of Western Brittany | Bidault-Toffin A.,University of Western Brittany | And 2 more authors.
Aquaculture | Year: 2013

The Gram-negative bacterium Vibrio harveyi is known to be highly pathogenic for the European abalone Haliotis tuberculata, which is a gastronomically important marine gastropod with a high commercial value. Since 1998, some particular bacterial strains are described as implicated in recurrent mortality outbreaks in French farm and field stocks of abalone. Recently, a 9.6. kb plasmid named pVCR1, was shown to be harbored by one highly V. harveyi virulent ORM4 strain suggesting its involvement in virulence phenotype. Thus, we have developed in the present study two TaqMan real-time PCR assays allowing to (i) rapidly and specifically detect, by a duplex procedure and in less than 2. h, both V. harveyi and the presence of plasmid pVCR1 from unidentified bacterial colony and to (ii) quantify both V. harveyi and the plasmid pVCR1 in the hemolymph of abalone or its surrounding seawater. Quantification curves of V. harveyi or ORM4 strain seeded in hemolymph or artificial sea water samples were equivalent showing excellent qPCR efficacies and detection level as low as 18. V. harveyi cell-equivalent genomic DNA in a PCR reaction well. This qPCR allowed us to monitor V. harveyi ORM4 strain in experimentally infected H. tuberculata. These diagnosis assays could provide powerful and useful tools to better understand the epidemiology of vibriosis caused by V. harveyi in different cultured marine species including H. tuberculata. © 2013 Elsevier B.V.

Bardon-Albaret A.,University of Southern Mississippi | Bardon-Albaret A.,Center Ifremer du Pacifique | Saillant E.A.,University of Southern Mississippi
Aquaculture | Year: 2016

The effects of hypoxic conditions and elevated ammonia concentrations on the viability of embryos and newly hatched larvae of the red snapper (Lutjanus campechanus) were investigated. In all experiments, tested levels of hypoxia or ammonia concentrations were applied to embryos and unfed newly hatched larvae from three different spawns. Exposures began at 1 h post fertilization (pf) and lasted until all individuals in a group had expired. Survival rates were monitored daily in duplicates for each spawn in each treatment. Fertilized eggs exposed to 2 mg L-1 dissolved oxygen (29% saturation) showed complete mortality before hatch while 81% of embryos in control groups (>85% saturation) hatched and subsequently maintained high survival until 5 days pf. Exposure to a moderate hypoxia (target 3 mg L-1, 43% saturation) reduced significantly the hatch rate and subsequent survival rates; the magnitude of the difference in survival rate between control and exposed groups increased from 10% at hatch to 45% at 5 days pf. When oxygen concentration was maintained high (83% saturation) until 36 h pf and then progressively reduced to reach 3 mg L-1 at 2 days pf, the survival of exposed embryos and larvae did not differ significantly from those recorded in control groups, although potential delayed or cumulative effects of the treatment after 4 days pf could not be evaluated in this experiment.Embryos exposed to 10 mg L-1 total ammonia (TA-N), which corresponded to unionized ammonia (UIA-N) concentrations ranging between 0.307 and 0.468 mg L-1 in the conditions of the experiment, exhibited significantly reduced hatch rates and complete mortality between 3 and 4 days pf; the latter period corresponds to the onset of exogenous feeding of red snapper. In contrast, control groups (TA-N < 0.26 mg L-1, UIA-N < 0.006 mg L-1) maintained high survival rates beyond 5 days pf indicating potential to successfully initiate exogenous feeding. Exposure to 1 mg L-1 TA-N (0.020 mg L-1 < UIA-N < 0.054 mg L-1) did not alter significantly survival with respect to control groups. Significant interactions between the spawn and the tolerance to hypoxia or elevated ammonia were detected in both experiments, indicating that variations among spawns need to be accounted for when determining safe levels for hatchery production. Statement of relevance: Achieving a reliable supply of high quality eggs and larvae is one of the main challenges of the developing marine aquaculture industry.Most studies to date have focused on maternal determinants of egg quality but the viability of embryos and newly hatched larvae can be impacted after fertilization if environmental conditions become unfavorable due to intensive hatchery conditions; this topic is poorly documented in marine fishes to date.This study provides data on the effects of two major stressors acting under high density culture (hypoxia and elevated ammonia concentration) on embryos and newly hatched larvae of the red snapper; the results highlight the importance to consider variations among spawns/parents when determining safe levels for hatchery production and also the high sensitivity of red snapper to these stresses, suggesting that this topic should be investigated in other marine offshore species.Relevance of the research to commercial aquaculture.The research contributes to control egg quality. © 2016.Elsevier B.V. All rights reserved.

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