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Differents aspects de la vie sociale des bacteries marines sont presentes ici, a la lumiere de la recherche publiee dans les dix dernieres annees sur les mecanismes adaptifs de l'adherence bacterienne et de la formation du biofilm, et sur leur importance dans les ecosystemes a tous les niveaux. Des modeles ecologiques « durables », comme les associations entre les grandes algues et la microflore marine, doivent etre developpes parallelement pour integrer les observations deja realisees in vitro sur des modeles simplifies, dans un contexte spatio-temporel naturel stabilise depuis des millions d'annees.

This Open Access book should have been published in January 2014, it still is under typesetting process; International audience; From 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.

Domoic acid (DA) was of no special scientific interest until a series of case studies revealed its role as the major marine neurotoxin causing amnesic shellfish poisoning (ASP). The analysis, toxicology, synthesis and degradation of the highly polar amino acid DA and its kainoid congeners are discussed in this chapter. Although DA is structurally simple and ubiquitous in contaminated food samples, it was not simple to prove that it was the causative agent of ASP in humans and of DA poisoning in carnivorous birds and mammals. Furthermore, its detection and the prevention of ASP requires regular monitoring of seafood using rapid and accurate analyses. The main producers of DA are certain seasonally blooming diatoms of the genus Pseudo-nitzschia, major components of coastal phytoplankton. Here, details are provided of the species most likely to be involved in food-poisoning episodes, together with a brief account of the molecular mechanisms that underlie DA toxicity, which cause symptoms of acute and chronic neurotoxicity. DA may attain critically toxic levels within two major food chains involving benthic filter-feeders (e.g., mussels) or planktivorous fish (e.g., anchovies). Preventive measures must be complemented by risk assessments of seasonal toxigenic blooms, especially in nutrient-enriched coastal areas. The major chemical and biotic factors that influence diatom bloom formation and toxigenicity are outlined. Genomics of DA production allow the development of novel molecular tools to better understand DA biosynthesis at the gene level, and the evolutionary significance of DA as a metabolite with primary and secondary characteristics.

We describe a protocol for preparing cultures of the PSP (paralytic shellfish poisoning) dinoflagellate Alexandrium minutum, towards subsequent studies of cell adhesion onto artificial substrates. First, phenotypic uniformity of the strain used and reproducibility of the standard growth profile are obtained by optimising key parameters. Batches of A. minutum at mid-exponential proliferation phase are radiolabeled with 33P-containing medium in order to later quantify cell adhesion. A mortality corrective index is applied to the latter, using the vital fluorochrome acridine orange, i.e. dead cells show no nuclear incorporation under epifluorescence microscopy.

International audience; Tropical 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.

International audience; Wild populations of brown marine algae (Phaeophyta) provide extensive surfaces to bacteria and epiphytic eukaryotes for colonization. On one hand, various strategies allow kelps prevent frond surface fouling which would retard growth by reducing photosynthesis and increasing pathogenesis. On the other hand, production and release of organic exudates of high energy value, sometimes in association with more or less selective control of settlement of epiphytic strains, allow bacteria to establish surface consortia not leading to macrofouling. Here, we present the analysis of adhesion and biofilm formation of bacterial isolates from the kelp Laminaria digitata and of characterized and referenced marine isolates. When they were grown in flow cell under standard nutrient regimes, all used bacteria, except one, were able to adhere on glass and then develop as biofilms, with different architecture. Then, we evaluated the effect of extracts from undisturbed young Laminaria thalli and from young thalli subjected to oxidative stress elicitation; this latter condition induced the production of defense molecules. We observed increasing or decreasing adhesion depending on the referenced strains, but no effects were observed against strains isolated from L. digitata. Such effects were less observed on biofilms. Our results suggested that L. digitata is able to modulate its bacterial colonization. Finally, mannitol, a regular surface active component of Laminaria exudates was tested individually, and it showed a pronounced increased on one biofilm strain. Results of these experiments are original and can be usefully linked to what we already know on the oxidative halogen metabolism peculiar to Laminaria. Hopefully, we will be able to understand more about the unique relationship that bacteria have been sharing with Laminaria for an estimated one billion years.

Loss of marine biodiversity seems inevitable in the 21st century. In benthic marine systems, survivors will have to acclimatize to seawater constantly increasing in temperature and evolving chemically, while also needing to out-compete new opportunistic neighbors and possibly facing increased predation pressure. Last but not the least, with a metabolism already pushed to its limits, survivors will have to fight against emerging diseases. The first section of this chapter is devoted to a presentation of the mechanisms involved in the climate-driven loss of coral reef biodiversity predicted within the next few decades in response to increasing anthropogenic pressure. Most of the arguments developed in the following sections reflect recent work published on reef-building corals, sponges and algae and their associated macro- and micro- biota, as major reef "engineers" (Wild et al., 2011). Biodiversity and chemodiversity have always been linked in the history of our planet. Both have undergone explosively creative periods, and at other times suffered dramatic losses or even extinctions followed by the emergence of better-adapted forms of life. The final part of this chapter is a reflection on how a few generations of humans have been able to overexploit the planet's biodiversity for their own immediate benefit, and harm it by producing and disseminating freak molecules and genomes for which the ocean is the final depository. We now need to apply our creativity or "intello-diversity" to preserving existing natural equilibriums to make the planet safe for future generations.

Recent developments in whole-cell spectroscopic methods allow rapid characterization of microorganisms of interest to human health, but have yet to be widely applied to marine microbiological studies. In this study of bacteria associated with the kelp Laminaria digitata, we have isolated 18 epiphytic bacterial strains from several thalli, sequenced their 16S rDNA, built corresponding phylogenetic trees, and characterized them using spectroscopic methods. Molecular taxonomy revealed Gram+ Actinobacteria and Gram− Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes. Twelve marine reference strains (Gram+ Firmicutes, and Gram− Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes) were treated accordingly. Whole-cell MALDI-TOF MS spectral profiles of 29 of the 30 strains were built into a database against which 16 replicate spectra of each strain were compared and categorized into groups. The proton HR-MAS NMR stack plots allowed visual delineation into taxonomic groups according to their most common peaks, in agreement with identifiable compounds from corresponding D2O solution spectra. With both methods, these groups corresponded to taxa identified by 16S rDNA sequences, MALDI-TOF MS being more discriminative than HR-MAS NMR. Culture age did not influence the spectral signatures in both approaches. Most cells grown under minimal conditions (VNSS medium) afforded HR-MAS NMR profiles markedly different to those grown in enriched conditions (ZoBell medium), indicating different adaptive metabolic responses between the two media. Spectral signatures obtained under strictly controlled conditions can be used as rapid and reliable tools for taxonomic purposes and as markers of physiological status.

Various aspects of the social life of bacteria are exposed here, in the light of recently published discoveries on the adaptive mechanisms of bacterial adhesion and biofilm formation, and on their importance at all ecological levels. There is now a need for studying models such as macrophytic algae and their associated microbial flora in order to integrate observations on simple laboratory models into the spatio-temporal perspective afforded by evolutionarily stable biocenoses.

On the basis of observations that biospecific random copolymers (RACS) could induce phenotypic changes on contact with selected eukaryotic or prokaryotic cell lines, polystyrene derivatives of known compositions and obtained by random substitutions of sodium sulfonate and of sulfamides of aspartic acid dimethyl ester, phenylalanine and leucine, were placed in contact with swimming dinophytes of the PSP toxin producing species Alexandrium minutum and of the non-toxic species Heterocapsa triquetra. A. minutum cells exhibited higher adhesion for the random copolymer made up of polystyrene (29%), polystyrene aspartic acid dimethyl ester sulfamide (47%) and polystyrene sodium sulfonate (24%), than for samples of this series with different compositions. In contrast to this, A. minutum adhesion remained very low throughout the phenylalanine and leucine copolymer series. These results indicate that the cell-substrate adhesion phenomenon is dependent upon the final composition of the copolymer, i.e. that it is composition-specific. Taxonomic specificity was then demonstrated by presenting the PSAspOMe copolymer series with cells of the non toxic species H. triquetra (Peridinialia) related to A. minutum (Gonyaulacacea), and by observing no specific association, i.e. no signal above background levels at any composition. Specific ligand-cell adhesion is evidenced for the first time between biospecific RACS and phytoplankton, which may inspire a new generation of structures to be used in aquaculture as protective nets over shellfish clusters, or as selective filtering devices to assist in shellfish depuration from toxic microalgae.

The sesquiterpene isocyanide stylotelline isolated from the marinesponge Stylotella sp. was assigned the structure 1a (absolute stereochemistry) on the basis of spectral - essentially 2D-NMR - and chemical data.

International audience; Until now, direct contact between a biological material and blood could be sustained for a short period of time, and typically required the administration of some heparin-based anticoagulant or antithrombotic treatment to prevent thrombosis. Other approaches have been explored in order to circumvent problems arising from the long-term use of these treatments. A new generation of polymers has been developed that are functionalized in order to specifically recognize key biological components. After introducing general issues of blood compatibility and introducing bioactive random copolymers (BIORACS) - a proprietary technology - a number of examples are provided that show the range of applications of BIORACS.

International audience; Marine seaweeds produce protective and defensive compounds, for example, carbohydrates and phenolic compounds that are a source of bioinspiration for molecules with cosmetic and human health applications. This chapter provides a general description of seaweeds, together with a brief overview of the adaptive and chemical defenses developed by these organisms. Among the great diversity of metabolites produced by seaweeds, we focus on specific carbohydrates (floridoside and mannitol) and phenolic compounds (mycosporine-like amino acids and phlorotannins) produced by macroalgae. Particular attention is paid to their highly variable chemical structure and methods for their extraction and purification. Their mechanisms of action are discussed, focusing on osmoregulation, desiccation, and photoprotection, which affect seaweed ecophysiology. Finally, we review their utility for cosmetology as moisturizers, sunscreens, and antiaging agents, for human health as wound dressings, and for skin regeneration. We point out the challenges faced when using these natural compounds in the cosmetic and human health sectors and the problems linked to the exploitation of this natural resource.

International audience; Te marine reservoir, with its massive biodiversity, likely harbors numerous human drug candidates. Polysaccharides of various marine origins have shown to be good alternatives to mammalian polysaccharides. One well-known example is heparin, a sulfated polysaccharide used in the prevention of thrombosis and pulmonary embolism. Te oldest use of marine polysaccharides concerns those produced by algae. Tese products form the basis for an economically important and expanding global industry. Tis chapter provides a historical background to the discovery of the therapeutic potential of these marine compounds, together with their medical and biotechnological applications. Peripheral arterial disease (PAD) is a progressive disorder due to atherosclerosis (narrowing of the peripheral arteries, especially in the legs). Arterial flow is reduced or discontinuous, causing oxygen deprivation in the underlying tissues and possible tissue necrosis. Te primary aim of medical therapy is to increase arterial flow in the affected limb in order to relieve pain, heal trophic lesions, and avoid amputation. Anticoagulant, antithrombotic, and antiplatelet agents are used to reduce the risk of thrombus formation. Novel treatments such as therapeutic angiogenesis (promotion of new blood vessel growth) are in the development phase, with promising preclinical data. Fucoidan is a polysulfated L-fucose endowed with biological activities closely related to its chemical composition (especially the distribution of sulfate groups along its polyfucose backbone) and to its molecular weight. Fucoidans are highly soluble in water, nontoxic, and non-immunogenic. Details are provided below on its production and characterization and on the main chemical characteristics that influence their biological activities. Fucoidan exhibits venous and arterial antithrombotic properties in animal models. In animal experiments, fucoidan promoted the formation of new blood vessels, thereby preventing necrosis of ischemic tissue. It also recruits stem cells from bone marrow, further accelerating tissue healing. Te cellular and molecular mechanisms underlying fucoidan’s effects on angiogenesis are then addressed, beginning with a brief overview of blood vessel formation. Recent advances have beenmade in understanding how the interactions between these polyfucoses and adult stem cells contribute to new blood vessel formation after ischemic injury, notably via carbohydrates located mainly in the basement membrane and cell surface.

International audience

International audience; A large proportion of the marine natural products actually under clinical investigation are peptide secondary metabolites with unusual amino acids residues. This growing family of compounds can be produced via two major pathways, ribosomal and nonribosomal. In this chapter are presented and illustrated, with a few famous examples, ribosomal- and nonribosomal-derived peptides. Attention is focused on five families of biologically active marine peptides of diverse origin, ranging from the oldest living cell of the world, the cyanobacteria, to more sophisticated organisms such as tunicates or mollusks. The discussed peptides illustrate differently the structural features and diversity found in marine-derived peptides; laxaphycins as an example of true peptides; dolastatins, didemnins and kahalalides are discussed in connection with their clinical trials; and azole/azoline-containing cyanobactins to exemplify the extraordinary chemical diversity within a single organism. Information about their biological properties and mechanisms of action is discussed when available.

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– α-proteobacteria, γ-proteobacteria and Bacteroidetes) were treated accordingly as controls. Molecular taxonomy of bacterial strains associated with L. digitata revealed Gram+ Actinobacteria and Gram– α-proteobacteria, γ-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 formation.; 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– α-proteobacteria, γ-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– α-proteobacteria, γ-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.