Publications by authors named "Christian Le Gall"

4 Publications

  • Page 1 of 1

Speciation of dissolved copper within an active hydrothermal edifice on the Lucky Strike vent field (MAR, 37 degrees N).

Sci Total Environ 2009 Jan 11;407(2):869-78. Epub 2008 Nov 11.

Ifremer centre de Brest, Département Etudes des Ecosystèmes Profonds, BP70, F-29280 Plouzané, France.

The objective of this study was to determine the concentrations of different fractions of dissolved copper (after filtration at 0.45 microm) along the cold part of the hydrothermal fluid-seawater mixing zone on the Tour Eiffel edifice (MAR). Dissolved copper was analyzed by stripping chronopotentiometry (SCP) after chromatographic C(18) extraction. Levels of total dissolved copper (0.03 to 5.15 microM) are much higher than those reported for deep-sea oceanic waters but in accordance with data previously obtained in this area. Speciation measurements show that the hydrophobic organic fraction (C(18)Cu) is very low (2+/-1%). Dissolved copper is present mainly as inorganic and hydrophilic organic complexes (nonC(18)Cu). The distribution of copper along the pH gradient shows the same pattern for each fraction. Copper concentrations increase from pH 5.6 to 6.5 and then remain relatively constant at pH>6.5. Concentrations of oxygen and total sulphides demonstrate that the copper anomaly corresponds to the transition between suboxic and oxic waters. The increase of dissolved copper should correspond to the oxidative redissolution of copper sulphide particles formed in the vicinity of the fluid exit. The presence of such a secondary dissolved copper source, associated with the accumulation of metal sulphide particles, could play a significant role in the distribution of fauna in the different habitats available at vents.
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http://dx.doi.org/10.1016/j.scitotenv.2008.09.056DOI Listing
January 2009

Fe analysis by the ferrozine method: Adaptation to FIA towards in situ analysis in hydrothermal environment.

Talanta 2005 Jun;66(5):1131-8

Ifremer Centre de Brest, DRO/EP, BP70, F-29280 Plouzané, France.

The target of this study is the adaptation of the ferrozine method to flow injection analysis (FIA) to perform iron analysis in situ using an in situ chemical analyser in hydrothermal environments. The adaptation of the method to FIA was followed by its optimisation using an experimental design screening method. The goals of the optimisation steps were to decrease the detection limit and to increase the measuring range to cope with the constraints of in situ analysis. The method allows the determination of iron in the mixing zone of hydrothermal fluid, enriched in iron, and seawater. A single manifold gives the possibility to analyse either Fe(II) or SigmaFe [Fe(II)+Fe(III)] in situ, or SigmaFe in the lab on hydrothermal seawater samples. The measuring range of the method was increased to up to 2000muM, which is coherent with the study of the chemical environment of communities associated with deep-sea hydrothermal activity. Finally, the method was applied in situ using the chemical analyser Alchimist during the ATOS cruise on hydrothermal vent fields on the Mid Atlantic Ridge.
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http://dx.doi.org/10.1016/j.talanta.2005.01.012DOI Listing
June 2005

Desulfurobacterium crinifex sp. nov., a novel thermophilic, pinkish-streamer forming, chemolithoautotrophic bacterium isolated from a Juan de Fuca Ridge hydrothermal vent and amendment of the genus Desulfurobacterium.

Extremophiles 2003 Oct 13;7(5):361-70. Epub 2003 May 13.

Laboratoire de Microbiologie et de Biotechnologie des Extrêmophiles, Département de Valorisation des Produits, IFREMER, Centre de Brest, BP70, 29280, Plouzané, France.

A novel thermophilic, chemolithoautotrophic bacterium, designated as NE1206(T), was isolated from a Juan de Fuca Ridge hydrothermal vent sample (tubes of the annelid polychaete Paralvinella sulfincola attached to small pieces of hydrothermal chimney). The cells were rod-shaped (1.2-3.5 x 0.4-0.7 microm), occurring as single motile rods or forming macroscopic aggregates visible as pinkish to brownish streamers. The new isolate was anaerobic. It grew between 50 and 70 degrees C (optimum 60-65 degrees C; doubling time approximately 1 h 15 min at 60 degrees C), between pH 5.0 and 7.5 (optimum pH around 6.0-6.5) and at sea salts concentrations between 20 and 40 g l(-1 )(optimum 30 g l(-1)). Cells grew chemolithoautotrophically in an H(2)/CO(2) atmosphere (80/20, v/v; 200 kPa). Molecular hydrogen was the sole electron donor used by the strain. Nitrate and elemental sulfur served as electron acceptors, yielding ammonia and hydrogen sulfide, respectively (nitrate reduction supported higher growth rates than sulfur reduction). The G+C content of the genomic DNA was 36.7+/-0.8 mol%. Phylogenetic analyses of the 16S rRNA gene located the strain within the genus Desulfurobacterium. However, the novel isolate possesses physiological and biochemical characteristics that differ from the previously described species of this genus. We propose that the isolate represents a novel species, Desulfurobacterium crinifex sp. nov. The type strain is NE1206(T) (DSM 15218(T), CIP 107649(T)). An amendment of the genus Desulfurobacterium description is proposed, based on the phenotypic characteristics of the novel species.
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http://dx.doi.org/10.1007/s00792-003-0329-4DOI Listing
October 2003

Seven cases of fungemia with Saccharomyces boulardii in critically ill patients.

Intensive Care Med 2002 Jun 10;28(6):797-801. Epub 2002 May 10.

Réanimation Polyvalente, Hospital Gilles de Corbeil, CH Sud-Francilien, 59 Boulevard Henri Dunant, 91106 Corbeil Essonnes Cedex, France,

Saccharomyces boulardii (Sb) is a particular strain of Saccharomyces cerevisiae (Sc). This viable yeast is used in intensive care adult patients, delivered in packets of 500 mg, for preventing diarrhea associated with antibiotics or enteral feeding at a regimen of 1-2 g/day. Between June 1996 and October 1998, seven cases of fungemia with Sb occurred in a 12-bed intensive care unit (ICU). All the patients concerned were severely ill patients, mechanically ventilated, treated by broad spectrum antibiotics with central venous catheter and were pretreated with Sb, except for one patient. In this study, Sb was identified by specific mycologic methods and confirmed the genomic identity between isolates of blood culture and yeasts from the treatment packets, contrary to a few other reports concerning Saccharomyces species published in international literature. The hypothesis discussed for explaining these cases of Sb fungemia are: (1) an intestinal translocation of Sb administered at a high dosage in severely ill patients, (2) a contamination of the central venous catheter, especially in the patient not pretreated with Sb and (3) a massive colonization of critically ill patients by the yeast as has been reported for Candida species. We note that cases of fungemia with Sc and Sb have become more and more frequent in the international literature during the last 10 years and we do not recommend administering Sb treatment in critically ill patients.
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http://dx.doi.org/10.1007/s00134-002-1267-9DOI Listing
June 2002