Bacterial communities associated with the wood-feeding gastropod <i>Pectinodonta</i> sp. (Patellogastropoda, Mollusca)

Even though their occurrence was reported a long time ago, sunken wood ecosystems at the deep-sea floor have only recently received specific attention. Accumulations of wood fragments in the deep sea create niches for a diverse fauna, but the significance of the wood itself as a food source remains to be evaluated. Pectinodonta sp. is a patellogastropod that exclusively occurs on woody substrates, where individuals excavate deep depressions, and is thus a potential candidate for a wood-eating lifestyle. Several approaches were used on Pectinodonta sampled close to Tongoa island (Vanuatu) to investigate its dietary habits. Host carbon is most likely derived from the wood material based on stable isotopes analyses, and high cellulase activity was measured in the digestive mass. Electron microscopy and FISH revealed the occurrence of two distinct and dense bacterial communities, in the digestive gland and on the gill. Gland-associated 16S rRNA gene bacterial phylotypes, confirmed by in situ hybridization, included members of three divisions (Alpha- and Gammaproteobacteria, Bacteroidetes), and were moderately related (90–96% sequence identity) to polymer-degrading and denitrifying bacteria. Gill-associated phylotypes included representatives of the Delta- and Epsilonproteobacteria. The possible involvement of these two bacterial communities in wood utilization by Pectinodonta sp. is discussed

Larval Transport Modeling of Deep-Sea Invertebrates Can Aid the Search for Undiscovered Populations

Background: Many deep-sea benthic animals occur in patchy distributions separated by thousands of kilometres, yet because deep-sea habitats are remote, little is known about their larval dispersal. Our novel method simulates dispersal by combining data from the Argo array of autonomous oceanographic probes, deep-sea ecological surveys, and comparative invertebrate physiology. The predicted particle tracks allow quantitative, testable predictions about the dispersal of benthic invertebrate larvae in the south-west Pacific. Principal Findings: In a test case presented here, using non-feeding, non-swimming (lecithotrophic trochophore) larvae of polyplacophoran molluscs (chitons), we show that the likely dispersal pathways in a single generation are significantly shorter than the distances between the three known population centres in our study region. The large-scale density of chiton populations throughout our study region is potentially much greater than present survey data suggest, with intermediate 'stepping stone' populations yet to be discovered. Conclusions/Significance: We present a new method that is broadly applicable to studies of the dispersal of deep-sea organisms. This test case demonstrates the power and potential applications of our new method, in generating quantitative, testable hypotheses at multiple levels to solve the mismatch between observed and expected distributions: probabilistic predictions of locations of intermediate populations, potential alternative dispersal mechanisms, and expected population genetic structure. The global Argo data have never previously been used to address benthic biology, and our method can be applied to any non-swimming larvae of the deep-sea, giving information upon dispersal corridors and population densities in habitats that remain intrinsically difficult to assess.Irish Research Council for Science, Engineering and TechnologyScience Foundation Irelan

Caractérisations par microscopie, spectroscopie et électrochimie d'un biofilm à partir d'une eau potable sur acier inoxydable

Nous avons suivi la formation d'un biofilm sur l'acier inoxydable (AISI 316) immergé dans un circuit d'eau potable pour deux températures (20 °C et 37 °C à pH = 8,25 – 8,5), à l'aide de techniques de caractérisation par spectroscopies : PM-IRAS (infrarouge de surface), XPS (spectroscopie des photons électrons X) ; par une analyse élémentaire : EDX (les rayons X à dispersion d'énergie) ; par microscopies : MEB (microscopie électronique à balayage) et AFM (microscopie à force atomique) ; et enfin, par électrochimie : RDE (voltammétrie sur électrode à disque tournant). Une étape de conditionnement de la surface de l'acier inoxydable a été mise en évidence, que nous avons suivie en fonction de la durée d'immersion et de l'influence de la température, et ce jusqu'à l'adhésion des premières colonies de bactéries. En eau froide (20 °C), l'étape de conditionnement varie de 1 à 8 jours, durant lesquels on détecte la présence de fonctions acides organiques superficielles adsorbées et ensuite viennent les liaisons peptidiques. À partir d'une dizaine de jours, on dénote la présence de polymères à la surface, et enfin des bactéries dont les longueurs sont comprises entre 2–3 μm, au bout de 12 jours. En revanche, cette étape de conditionnement se réduit à 2 jours en eau tiède (37 °C), durant lesquels des carbonates, des fonctions acides superficielles et des fonctions peptidiques sont détectables. Une grande variété de bactéries a été imagée dans le biofilm, incluant vraisemblablement des légionelles. Une épaisseur limite de 4 μm a aussi été estimée pour une durée de 3 mois dans une eau froide. La combinaison de ces différentes techniques permet de mettre en évidence une succession d'étapes avant l'adhésion bactérienne sur l'acier en eau potable

Identification of natural sunken wood samples.

Sunken woods are abundant in deep oceanic environments, housing a huge faunal diversity. Studies on that substrate firstly focused on the associated organisms, but since a few years, identification of wood is a further aim. The purpose is to appreciate its degradation state, diversity, geographical origin and to identify specific associations between colonizing organisms and substrates. The first determinations were made on sunken woods from Taiwan/Philippines, the Vanuatu Archipelago, and the Mediterranean Sea. Samples’ identification was based on histological studies. Different preparation techniques were used, depending on their degradation state. Detailed anatomy descriptions were made and compared to the native flora and the introduced species. Wood samples were well preserved. Diversified species were encountered, seemingly originating from local floras. In situ settlements of known wood species will enhance the knowledge of degradation and colonization degrees

Colonization Of Organic Substrates Deployed In Deep-Sea Reducing Habitats By Symbiotic Species And Associated Fauna

International audienceIn this study, our goal was to test whether typical vent/seep organisms harbouring symbionts or not, would be able to settle on organic substrates deployed in the vicinity of chemosynthetic ecosystems. Since 2006, a series of novel standardized colonization devices (: osynthetic cosystem lonization by arval nvertebrates) filled with three types of substrates (wood, alfalfa and carbonate) have been deployed in different types of reducing habitats including cold seeps in the eastern Mediterranean, a mud volcano in the Norwegian Sea, and hydrothermal vents on the Mid-Atlantic Ridge for durations of 2 weeks to 1 year. For all deployments, highest species diversities were recovered from CHEMECOLIs filled with organic substrates. Larvae from species associated with thiotrophic symbionts such as thyasirid, vesicomyid and mytilid bivalves, were recovered in the eastern Mediterranean and at the Mid-Atlantic Ridge. At the Haakon Mosby Mud Volcano, larvae of symbiotic siboglinids settled on both organic and carbonate substrates. Overall, novel colonization devices (CHEMECOLI) filled with organic substrates attracted both fauna relying on chemosynthesis-derived carbon as well as fauna relying on heterotrophy the latter being opportunistic and tolerant to sulphide

Electrodeposition of Polypyrrole in TiO₂ Nanotube Arrays by Pulsed-Light and Pulsed-Potential Methods

Using highly ordered TiO₂ nanotube arrays as the substrate for electropolymerization provides a high surface area for polymer deposit and vertical pathways for electron transport. The challenge is to deposit the polymer on the inner and outer walls of the tubes and to avoid the sealing of the tubes at the mouth. Ideally, this situation could be reached by filling the tubes from the bottom. We demonstrate here that by using pulsed methods (light pulses, potential pulses), the deposition rate can be controlled, leading to a better monomer supply within the nanotubular matrix. The parameters to apply for the deposition are greatly dependent on the nature of the anion in the electrolyte, which determines the rate and the location of the polymer growth at the electrolytic solution/semiconductor interface