Marine Biodiversity and Chemodiversity — The Treasure Troves of the Future

This Open Access book should have been published in January 2014, it still is under typesetting processInternational audienceFrom cyanobacteria and bacteria to the largest metazoans, chemistry is the preferred mode of aquatic communication, thanks to the extraordinary solvation properties of water. Bacteria create biofilms inside which they communicate using their own chemical repertoire before colonizing new media, substrates or organisms. Microalgae form blooms which are maintained by releasing semiochemicals for cell-cell recognition. Fish rely on their extraordinary sense of smell to hunt or to migrate to some specific breeding spot. The extraordinary biodiversity of coral reefs is maintained by a highly complex chemical network of toxins and pheromones, some soluble, some dispersed with a mucus carrier or surface-coated. But not only: the amazing colors used for warning or for camouflage, the bioluminescence used in the dark correspond to very sophisticated assemblages of pigments, small metabolites or proteins, each organism having its own strategy to be visually recognized or to blend into the background. Humans have only recently been aware of the extraordinary potential marine molecules for the design of new drugs, cosmetics and nutraceutics. Well over 20000 natural molecules have been studied so far, and several have responded to the need for novel anticancer, antibiotic, anti-inflammatory or anti-pain agents etc. To-date, very little is said or written on the fate of natural chemodiversity within the context of local or general biodiversity collapse, both terrestrial and marine. After a brief historical account of the intricate connections between chemodiversity and biodiversity since life appeared on our planet, this chapter attempts to demonstrate that natural molecular diversity, both mineral and organic, is a treasure to preserve for future generations, using a series of marine examples

Novel Tools for the Evaluation of the Health Status of Coral Reefs Ecosystems and for the Prediction of Their Biodiversity in the Face of Climatic Changes

International audienceTropical reefs concentrate between one quarter and one third of the total marine biodiversity, though they only cover about 0.1% of the global oceanic surface and are confined to warmer latitudes. Half a billion humans depend partly or totally on the goods and services provided by coral reef ecosystems. However, coral reefs are now recognized as being among the most fragile of all environments in the face of localized anthropic pressures and of their climatic consequences of planetary dimensions. Today less than 20% can still be regarded as unharmed. Research scientists continue to explore natural biodiversity in remote pristine environments (especially biodiversity hotspots, a very useful conservation-promoting concept) and to observe its lossesin degrading habitats. Programs on bioremediation of impacted sites are attracting funds, and classification of natural habitats as protected sites is gaining public support. Yet the scientific community has very little leverage on the decision-making of potentially impacting industrial, commercial and urban development projects, and on the say-so broadcast by their promoters in the media. In this chapter, a holistic concept is proposed that (i) integrates cutting-edge molecular research and standard technologies with field sampling and laboratory simulations of natural habitats (ii) using holobiont-based sentinel systems, (iii) into a single tool that "shows evidence" of ongoing degradation rather than aftermath "score loss". Corrective action can then be taken in specific directions before no-return limits have been reached and total ecosystem collapse is on the way

The Halogenated Metabolism of Brown Algae (Phaeophyta), Its Biological Importance and Its Environmental Significance

Brown algae represent a major component of littoral and sublittoral zones in temperate and subtropical ecosystems. An essential adaptive feature of this independent eukaryotic lineage is the ability to couple oxidative reactions resulting from exposure to sunlight and air with the halogenations of various substrates, thereby addressing various biotic and abiotic stresses i.e., defense against predators, tissue repair, holdfast adhesion, and protection against reactive species generated by oxidative processes. Whereas marine organisms mainly make use of bromine to increase the biological activity of secondary metabolites, some orders of brown algae such as Laminariales have also developed a striking capability to accumulate and to use iodine in physiological adaptations to stress. We review selected aspects of the halogenated metabolism of macrophytic brown algae in the light of the most recent results, which point toward novel functions for iodide accumulation in kelps and the importance of bromination in cell wall modifications and adhesion properties of brown algal propagules. The importance of halogen speciation processes ranges from microbiology to biogeochemistry, through enzymology, cellular biology and ecotoxicology

Rencontres avec les bactéries marines

Différents aspects de la vie sociale des bactéries marines sont présentés ici, à la lumière de la recherche publiée dans les dix dernières années sur les mécanismes adaptifs de l adhérence bactérienne et de la formation du biofilm, et sur leur importance dans les écosystèmes à tous les niveaux. Des modèles écologiques "durables", comme les associations entre les grandes algues et la microflore marine, doivent être développés parallèlement pour intégrer les observations déjà réalisées in vitro sur des modèles simplifiés, dans un contexte spatio-temporel naturel stabilisé depuis des millions d'années

Interactions entre la macroalgue brune Laminaria digitata et ses épibiontes bactériens (études moléculaire et spectroscopiques)

Il est désormais admis que toute surface immergée en eau de mer est rapidement couverte d un biofilm marin, suivi pour certaines de macrosalissures, essentiellement composées d organismes marins vivants. Les thalles de macroalgues fournissent des surfaces importantes à la formation de biosalissures. Cependant, leur surface reste la plupart du temps exempt de macrosalissures, peut-être en relation avec leur succès évolutif, montrant leurs multiples stratégies de cohabitation avec leurs colonisateurs. Les macroalgues sont donc des modèles naturels de choix, susceptibles d inspirer des solutions originales aux problèmes causés par les biofilms marins. Dans cette étude sur les bactéries associées aux thalles de l algue brune Laminaria digitata, connue pour avoir un métabolisme halogéné particulier, nous avons isolé 18 souches bactériennes épiphytes, séquencé leur ADNr 16S et construit l arbre phylogénétique correspondant. Puis nous les avons caractérisées par des méthodes spectroscopiques et étudié leur comportement d adhésion et de formation de biofilm en présence de composés provenant de l algue. Douze souches bactériennes marines de référence (Gram+ Firmicutes, et Gram a-proteobacteria, g-proteobacteria et Bacteroidetes) ont été traitées de la même manière. La taxonomie moléculaire des souches associées à L. digitata a révélé des bactéries à Gram+ Actinobacteria et à Gram a-proteobacteria, g-proteobacteria et Bacteroidetes. Une base de données de profils spectraux des 30 souches a été construite en spectrométrie de masse MALDI-ToF à partir de cellules bactériennes entières. La signature spectrale propre à chaque souche bactérienne s est révélée être un outil rapide et fiable à des fins taxonomiques. Les profils spectraux obtenus en RMN HR-MAS, également à partir de cellules entières, s est avérée moins discriminante taxonomiquement que la MALDI-ToF. Cependant, les signatures spectrales variant en fonction du milieu de culture utilisé, la RMN HR-MAS s est révélée être un outil utile dans l étude des réponses d adaptation physiologique bactérienne à l environnement. Les souches bactériennes ont montré un pouvoir d adhésion en microplaques en eau de mer filtrée stérile et de formation de biofilm en milieu ZoBell spécifique à la souche. Ces pouvoirs d adhésion et de formation de biofilm pouvaient être plus ou moins sensible (augmenté ou diminué) lorsque des métabolites extraits et des exsudats de l algue ont été co-incubés avec les souches. Les bactéries associées à L. digitata ont été plus sensibles aux exsudats d algue que les bactéries de référence, avec un effet majoritairement négatif sur l adhésion et la formation de biofilm. Les métabolites extraits avec des solvants organiques, présents à la surface et dans l algue, ont un effet majoritairement négatif sur l adhésion de bactéries associées à l algue, et positif sur l adhésion des bactéries de référence. Enfin, des métabolites purs ont également été testés sur ces différentes souches, impliquant des réponses d adhésion et de formation de biofilm propre à chaque souche.Once immersed in natural seawater, any surface will be rapidly colonized by biofilm forming bacteria, which tend to favour the establishment of sessile invertebrates, algae and protists as assemblages that cause macrofouling. Macrophytic algae represent very large surfaces for potential colonization by microbial and fouling epibionts. Yet actively growing parts are conspicuously devoid of visible epiphytism presumably as a consequence of their evolutionary success based on a life long history of cohabitation with marine bacteria and other colonizers. As such, algae represent choice models upon which original antifouling biotechnologies may find inspiration. Our study is centered on the kelp Laminaria digitata which enjoys a unique metabolism featuring iodine and bromine processing haloperoxidases, and on its bacterial epiflora. We have isolated 18 cultivatable epiphytic strains of bacteria from selected surfaces of the thallus, we have sequenced their ADNr 16S, and we have built the corresponding phylogenetic tree from matches with online databases. Then, we characterized each strain from intact cell preparations by recording their proteome and their metabolome signature spectra, and finally we studied the adhesion and biofilm forming capabilities of selected strains when exposed to metabolites produced by their L. digitata host. Twelve marine reference strains isolated from inert surfaces (Gram+ Firmicutes, and Gram a-proteobacteria, g-proteobacteria and Bacteroidetes) were treated accordingly as controls. Molecular taxonomy of bacterial strains associated with L. digitata revealed Gram+ Actinobacteria and Gram a-proteobacteria, g-proteobacteria and Bacteroidetes. A spectral databank of 30 strains was built from MALDI-ToF mass spectra from entire cell preparations and the resulting individual signatures were found reliable and fast as taxonomic markers at the strain level. Spectral signatures obtained by proton HR-MAS NMR from intact cell preparations was less discriminative than MALDI-ToF in terms of attribution but quite informative as regards to variations in cultivation parameters and associated physiological responses on behalf of the bacteria. Adhesion and biofilm formation studies on selected strains showed that these processes are strain-specific under standard experimental conditions. Adhesion and biofilm could be modulated (up or down) by addition of exudates and metabolite extracts from L. digitata that were solubilized in the medium of bacterial strains. Strains naturally associated with L. digitata were more responsive to exposure to exudates than the environmental reference strains, the global effect being negative. Surface and tissue organic extracts had a globally negative effect on adhesion of bacteria naturally associated with L. digitata, but showed a positive effect on the adhesion of reference bacteria. Finally, individual metabolites were tested with these bacterial strains, involving strain-specific responses of adhesion and biofilm formationLORIENT-BU (561212106) / SudocROSCOFF-Observ.Océanol. (292393008) / SudocSudocFranceF

Mycosporine-Like Amino Acids (MAAs) in Biological Photosystems

International audienc

Marine Natural Products from New Caledonia—A Review

International audienceMarine micro-and macroorganisms are well known to produce metabolites with high biotechnological potential. Nearly 40 years of systematic prospecting all around the New Caledonia archipelago and several successive research programs have uncovered new chemical leads from benthic and planktonic organisms. After species identification, biological and/or pharmaceutical analyses are performed on marine organisms to assess their bioactivities. A total of 3582 genera, 1107 families and 9372 species have been surveyed and more than 350 novel molecular structures have been identified. Along with their bioactivities that hold promise for therapeutic applications, most of these molecules are also potentially useful for cosmetics and food biotechnology. This review highlights the tremendous marine diversity in New Caledonia, and offers an outline of the vast possibilities for natural products, especially in the interest of pursuing collaborative fundamental research programs and developing local biotechnology programs