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Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp Rimicaris exoculata
1Université de Liège, Laboratoire de Morphologie fonctionnelle et évolutive, Unité de Morphologie ultrastructurale et Cellule d'Appui Technologique en Microscopie (Catμ), allée de la chimie, 3, 4000 Liège, Belgium
2Laboratoire de Microbiologie et Biotechnologie des Extrêmophiles, Ifremer, centre de Brest, BP 70, 29280 Plouzané, France
3Department of Chemistry, Missouri University of Science and Technology, University of Missouri-Rolla, Rolla, Missouri 65409-0010, USA
4Department of Physics, B5, University of Liège, 4000 Sart-Tilman, Belgium
5UMR CNRS 7138 "Systématique, Adaptation et Evolution", Université Pierre et Marie Curie, 7 Quai St Bernard, Bâtiment A, 75252 Paris Cedex 05, France
Abstract. The Rimicaris exoculata shrimp is considered a primary consumer that dominates the fauna of most Mid-Atlantic Ridge (MAR) hydrothermal ecosystems. These shrimps harbour in their gill chambers an important ectosymbiotic community of chemoautotrophic bacteria associated with iron oxide deposits. The structure and elemental composition of the minerals associated with these bacteria have been investigated by using X-ray microanalyses, light microscopy, and transmission, environmental scanning and scanning transmission electron microscopy. The nature of the iron oxides in shrimps obtained from the Rainbow vent field at 36°14.0' N, has also been determined by Mössbauer spectroscopy. This multidisciplinary approach has revealed that the three step-levels of mineral crust found in the Rimicaris exoculata shrimps consist of heavy concretions formed by nanoparticles of two-line ferrihydrite intermixed with minor inorganic SiO2, (Ca,Mg)SO4, and (Ca,Mg)3(PO4)2 minerals that may stabilise the ferrihydrite form of iron oxides. Morphological observations on the bacteria have revealed their close interactions with these minerals and, thus, indicate the biogenic origin of the iron oxide deposits. The evolution of the bacterial density in the three mineral crust levels is related to the amount of the iron deposits and it is proposed that the lower crust level is the most likely region for the location of the iron-oxidizing bacteria.
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Citation: Corbari, L., Cambon-Bonavita, M.-A., Long, G. J., Grandjean, F., Zbinden, M., Gaill, F., and Compère, P.: Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp Rimicaris exoculata, Biogeosciences Discuss., 5, 1825-1865, 2008. Bibtex EndNote Reference Manager
