Postdoc position, Nantespostdoc position in Nantes

Development of the valuable antimicrobial Haslea and marennine for aquaculture (ValHalla)


The marine diatom Haslea ostrearia is known for its ability to produce a water-soluble blue-green pigment, marennine. This pigment is responsible for the greening of oysters matured in the oyster ponds in western France. The physiology of this diatom, its sexual reproduction and life cycle have been studied by members of our research team (Mouget et al. 1999, 2004, 2009; Davidovich et al. 2009). Marennine’s synthesis (intracellular form, IMn) and its release (extracellular form, EMn) into the environment depend on many factors, including light intensity and quality, and appear to be increased by some nutrient deficiencies (Robert et al. 2002; Mouget et al. 2005). A method for the purification and quantification of IMn and EMn has been developed (Pouvreau et al. 2006a), and numerous biochemical characterization tests have made it possible to show that these molecules are partially polyphenolic (Pouvreau et al. 2006b) and glycosidic (Gastineau et al. 2014).

Marennine is also a bioactive molecule, whose properties could be valued, particularly in aquaculture. Indeed, previous studies have demonstrated that purified marennine has allelopathic (Pouvreau et al. 2007), antioxidant (Pouvreau et al. 2008), antiproliferative, anti-bacterial and anti-viral properties (Gastineau et al. 2012b ; 2014). Antibacterial properties were observed using several species of "terrestrial" (Staphylococcus aureus, Escherichia coli) or marine bacteria (Pseudoalteromonas elyakowi, Polaribacter irgensii, Vibrio anguillarum, V. aestuarianus, V. splendidus), while for antiviral properties, Herpes simplex virus 1 (HSV-1) was used (Gastineau et al. 2012b; 2014). These neutralizing effects on Vibrio-type bacterial agents are of great interest in aquaculture. Indeed, these pathogens affect many farmed species, fish, crustaceans and bivalves (Diggles et al. 2000; Sung et al. 2001) and are involved in mass mortality events in oyster aquaculture (Garnier et al. 2008), but also in larval breeding of various bivalve species (Nicolas et al. 1996; Elston et al. 2008). More generally, it would appear that all marennine-type pigments exhibit antibacterial and antiviral activities, as demonstrated with the newly described blue diatom species H. karadagensis (Gastineau et al. 2012a).


Objectives of the ValHalla project

In order to demonstrate the protective effect of marennine-like blue pigments and promote their use at the industrial level, we seek a post-doctoral researcher (co-funding UBL - H2020 GHaNA programme, see below). The post-doctoral contract being funded for one year the ValHalla project will focus only on bivalve models. The recruited candidate will be responsible for studying the effectiveness of marennine-like blue pigments and their mechanisms of action on the immunity of commercial bivalves (oysters, mussels, clams, scallops) and host-pathogen interactions, using various approaches as:

-          Effect on microbial growth and virulence.

-          Effect on systemic and mucosal immunity

-          Effect on bivalve microbiomes

-          Effect on disease development and mortality

-          Effect on bivalve physiology (filtration, respiration, assimilation)

Direct and indirect activities against different bacterial pathogens related to aquaculture will be tested on several bivalve species at different ontogenic stages (mainly larvae and juveniles, but also on adults if time is sufficient).

In a first step, the minimum toxic concentration of pigments will be tested on pure pathogens, then on bivalves, and finally in challenge tests to determine the protective effect. In addition to the evaluation of the direct effects of marennine on the growth and virulence of ecologically and economically important marine pathogens, the effect of the pigment and Haslea cultures on bivalve immunity will be evaluated by focusing on cellular and humoral antimicrobial processes. The effect of marennine and Haslea cultures on the resistance of bivalves to bacterial infections will be tested in vivo using naturally and experimentally infected bivalves. This is of ever-greater importance given the current lack of prophylactic treatment for bivalve diseases and the increase in antibiotic resistance.


Contributions of H2020 GHaNA

 WP7 "Application in Aquaculture",  is intended to evaluate the use of Haslea and marennine as a means to reduce the impact of infectious diseases in aquaculture operations. Under this WP, the growing conditions of blue Haslea strains allowing optimal production of marennine or marennine-type pigments will be determined under "real" operating conditions for different bivalves (oysters, clams, scallops and mussels) and fishes (e. g. plaice) produced in hatcheries and nurseries, according to the geographical origin of the strain.

To achieve the objectives of the ValHalla project, the recruited candidate will be entitled to financial support from the GHaNA programme at the operational level, and to mobility to different international partners of the GHaNA consortium involved in WP7 (e.g. ISMER, UQAR; Marine Disease Laboratory, Stony Brook University). In addition, IFREMER being also a partner in the GHaNA project, the recruited candidate will have access to the resources of the Bouin Regional Innovation Platform (PRI) for the in vivo evaluation of anti-vibrio activities of marennine and the realization of challenge tests.


Expected profile

The candidate must have good zootechnical skills for the breeding of aquatic/marine organisms and phytotechnical skills for the cultivation of microalgae. He/she will also have to demonstrate solid expertise in the fields of animal and plant ecophysiology.

Knowledge of histochemistry techniques and anti-bacterial activity measurements will be appreciated.


Impact of the project

In aquaculture, larval stages are generally the most sensitive to viral or bacterial infections. The use of natural antibacterial substances, particularly of microalgal origin, represents a credible alternative to the use of antibiotics, the misuse of which results in the emergence of cases of multi-resistance in certain bacteria.



Davidovich N.A., Mouget J.-L. & Gaudin P. 2009. Heterothallism in the pennate diatom Haslea ostrearia. European Journal of Phycology, 44 : 251-261

Diggles B.K., Carson J., Hine P.M., Hickman R.W., Tait M.J. 2000. Vibrio species associated with mortalities in hatchery-reared turbot (Colistium nudipinnis) and brill (C. guntheri) in New Zealand Aquaculture, 183 : 1-12

Elston R. A.,HasegawaH., Humphrey K. L., Polyak I.K., Häse C.C. 2008. Re-emergence of Vibrio tubiashii in bivalve shellfish aquaculture: severity, environmental drivers, geographic extent and management. Diseases of Aquatic Organisms 82:119–134.

Garnier, M., Labreuche, Y., Nicolas, J. L., 2008. Molecular and phenotypic characterization of Vibrio aestuarianus subsp. francensis subsp. nov., a pathogen of the oyster Crassostrea gigas. Systematic and Applied Microbiology 31, 358- 365.

Gastineau R., Hardivillier Y., Leignel V., Morançais M., Fleurence J., Hellio C., Bourgougnon N., Davidovich N.A., Tekaya N., Gaudin P., Mouget J.-L. 2012a. Greening effect on oysters and biological activities of the blue pigment produced by the diatom Haslea karadagensis (Naviculaceae). Aquaculture, 368-369 : 61-67.

Gastineau R., Pouvreau J.-B., Hellio C., Morançais M., Fleurence J., Gaudin P., Bourgougnon N., Mouget J.-L. 2012b. Biological activities of purified marennine, the blue pigment responsible for the greening of oysters. Journal of Agricultural and Food Chemistry 60 : 3599-3605.

Gastineau R., Turcotte F., Pouvreau J.-B., Morançais M., Fleurence J., Winarto E., Semba Prasetiya F., Arsad S., Jaouen P., Babin M., Coiffard L., Couteau C., Bardeau J.-F., Jacquette B., Leignel V., Hardivillier Y., Marcotte I., Bourgougnon N., Tremblay R., Deschênes J-S., Badawy H., Pasetto Davidovich N.A., Hansen G., Dittmer J., Mouget J.-L. 2014. Marennine, promising blue pigments from a widespread Haslea diatom species complex. Marine Drugs 12 : 3161-3189.

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Mouget J.-L., Rosa P., Vachoux C. & Tremblin G. 2005. Enhancement of marennine production by blue light in the diatom Haslea ostrearia. Journal of Applied Phycology, 17 : 437-445.

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Pouvreau J.-B., Morançais M., Rosa P., Robert J.-M., Fleurence F., Pondaven P. 2006a. Purification of the blue-green pigment “marennine” from the marine tychopelagic diatom Haslea ostrearia (Gaillon/Bory) Simonsen Journal of Applied Phycology 18:769–781

Pouvreau J.-B., Morançais M., Fleury F., Rosa P., Thion L., Cahingt B., Zal F., Fleurence F., Pondaven P. 2006b. Preliminary characterisation of the blue-green pigment “marennine” from the marine tychopelagic diatom Haslea ostrearia (Gaillon/Bory) Simonsen. Journal of Applied Phycology 18:757–767

Pouvreau J.-B., Housson E., Le Tallec L., Morançais M., Rincé Y., Fleurence F., Pondaven P. 2007. Growth inhibition of several marine diatom species induced by the shading effect and allelopathic activity of marennine, a blue-green polyphenolic pigment of the diatom Haslea ostrearia (Gaillon/Bory) Simonsen Journal of Experimental Marine Biology and Ecology 352 212–225

Pouvreau J.-B., Morançais M., Taran F., Rosa P., Dufossé L., Guérard F., Pin S., Fleurence F., Pondaven P. 2008. Antioxidant and Free Radical Scavenging Properties of Marennine, a Blue-Green Polyphenolic Pigment from the Diatom Haslea ostrearia (Gaillon/Bory) Simonsen Responsible for the Natural Greening of Cultured Oysters. Journal of Agricultural and Food Chemistry 56, 6278–6286.

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Sung H.-H., Hsu S.-F., Chen C.-K., Ting Y.-Y., Chao W.-L. 2001. Relationships between disease outbreak in cultured tiger shrimp (Penaeus monodon) and the composition of Vibrio communities in pond water and shrimp hepatopancreas during cultivation. Aquaculture 192 (2-4): 101-110