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| Titel |
Inorganic carbon incorporation and nutritional transfers in the chemosynthetic ectosymbiosis harboured by the Atlantic hydrothermal vent shrimp Rimicaris exoculata |
| VerfasserIn |
Julie Ponsard, Marie-Anne Cambon-Bonavita, Magali Zbinden, Gilles Lepoint, André Joassin, Laure Corbari, Bruce Shillito, Philippe Compère |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047356
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| Zusammenfassung |
| The hydrothermal vent shrimp Rimicaris exoculata is characterized by its chemoautotrophic
bacteria hosted in its gill chambers. It lives in dense swarms of thousands individuals per m2
on the black smoker chimneys of the Mid-Atlantic Ridge (MAR) vent sites, including the
Rainbow site (36Ë 13’N MAR) where we sampled. First considered as a monoculture of a
single phylotype of sulphide-oxidizing epsilon-proteobacteria (Polz & Cavanaugh, 1995), the
R. exoculata symbionts are recognized as forming real bacterial community that includes
various phylotypes and metabolisms. Zbinden et al. (2008) and Petersen et al. (2010) have
identified genes characteristic of methane–oxidizing and sulphide–oxidizing bacteria in the
shrimp gill chambers. Furthermore, they observed the occurrence of intracellular
sulphur– and iron–enriched granules in filament and rod bacteria, and identified some
methanotrophic–like bacteria cells, suggesting that at least three metabolisms (iron,
sulphur and methane oxidation) co–occur within the ectosymbiotic community.
On the other hand, Schmidt et al. (2008) also pointed out that several reducing
compounds present in the hydrothermal environment (H2, CH4, Fe2+ or SH-)
could be used as geochemical energy sources for the shrimp bacterial growth and
CO2-fixation.
The major aims of the work were to determine the environmental reducing compounds
really used by ectosymbiotic bacteria of R. exoculata as energy supply of their metabolism
and to highlight the probable transfer of molecules from bacteria to the shrimp tissues. In the
experiments, shrimps were incubated alive in small volumes in pressurized aquarium
IPOCAMPTM either for 4, 6 or 10 hours with various reducers (H2, CH4, Fe2+,
thiosulphate) and in presence of carbon isotope-labelled Na-bicarbonate (NaH13CO3or
NaH14CO3). Other experiment was also realized by 1 hour-incubation of shrimps in
seawater in presence of 14C-acetate and 3H-lysine. Preferential metabolism and carbon
incorporation in the biofilm in the shrimp gill chamber was determined through the
quantification of 13C in mass spectrometry and by scintillation counting for 14C. The
first data carbon-isotope incorporation allows identifying Fe2+ and thiosulphate as
suitable energy sources for the bacteria. They also suggest the presence of an internal
energy supply in the bacteria owing the carbon fixation also occurs over several
hours in pure seawater. The sulphur granules observed in the bacteria reported by
Zbinden et al. (2008) could be the energy source used. The possible transfer of organic
molecules from the bacterial symbionts to the host shrimp was also investigated by
examining the 13C, 14C and 3H levels in the tissues. The presence of 14C and 3H
incorporated from 14C-bicarbonate, 14C-acetate and 3H-lysine confirm the transfer and the
higher levels of radioactivity in the gill chamber integuments support a probable
tegumental incorporation pathway of dissolved organic molecules rather than a digestive
pathway.
The authors thank the National Fund for Scientific Research (FNRS-FRIA, Belgium)
(conv. FRFC No 2.4.594.07.F, fellowships of Dr L. Corbari and J. Ponsard), and the French
Institutes (CNRS and IFREMER) for their financial support.
References: Petersen et al., Environmental Microbiology, (2010) 1-15; Polz &
Cavanaugh, Proc. Natl. Acad. Sci.., 92 (1995) 7232-7236; Schmidt et al., Mar. Chem.,
108 (2008) 18–31; Zbinden et al., Exp. Mar. Biol. and Ecol., 359 (2008) 131–140 |
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