Active archaeal communities at cold seep sediments populated by Siboglinidae tubeworms from the Storegga Slide.

Siboglinid tubeworms in cold seep sediments can locally modify the geochemical gradients of electron acceptors and donors, hence creating potential microhabitats for prokaryotic populations. The archaeal communities associated with sediments populated by Oligobrachia haakonmosbiensis and Sclerolinum contortum Siboglinid tubeworms in the Storegga Slide were examined in this study. Vertical distribution of archaeal communities was investigated using denaturing gradient gel electrophoresis based on 16S rRNA genes.

In vivo RNA interference in oyster--vasa silencing inhibits germ cell development.

This study investigated the potential of RNA interference, which is technically challenging in bivalve mollusc species, to assess gene function in the oyster Crassostrea gigas. We designed dsRNA targeting the oyster vasa-like gene (Oyvlg), specifically expressed in oyster germ cells. In vivo injection of oyvl-dsRNA into the gonad provokes a knockdown phenotype corresponding to germ cell underproliferation and prematurely arrested meiosis througout the organ.

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

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.

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

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.

Ontogenic effects of early feeding of sea bass (Dicentrarchus labrax) larvae with a range of dietary n-3 highly unsaturated fatty acid levels on the functioning of polyunsaturated fatty acid desaturation pathways.

Four replicated groups of sea bass (Dicentrarchus labrax) larvae were fed diets containing an extra-high level of highly unsaturated fatty acids (HUFA) (XH; 3.7 % EPA+DHA), a high level of HUFA (HH; 1.7 %), a low level of HUFA (LH; 0.

Desulfurobacterium atlanticum sp. nov., Desulfurobacterium pacificum sp. nov. and Thermovibrio guaymasensis sp. nov., three thermophilic members of the Desulfurobacteriaceae fam. nov., a deep branching lineage within the Bacteria.

Three thermophilic, anaerobic, strictly chemolithoautotrophic, sulphur- and/or thiosulphate-reducing bacteria, designated SL17(T), SL19(T) and SL22(T), were isolated from deep-sea hydrothermal samples collected at 13 degrees N (East Pacific Rise), Guaymas Basin (Gulf of California) and 23 degrees N (Mid-Atlantic Ridge), respectively. These strains differed in their morphology, temperature range and optimum for growth, energy substrates and 16S rRNA gene sequences. The G+C content of the genomic DNA was 41 mol% (SL22(T)), 42 mol% (SL17(T)) and 46 mol% (SL19(T)).

An amylase gene polymorphism is associated with growth differences in the Pacific cupped oyster Crassostrea gigas.

This study investigated the non-neutrality of genetic polymorphism in two alpha-amylase genes (AMYA and AMYB) in the oyster Crassostrea gigas. Bi-parental oyster families, bred to be polymorphic for markers in these genes, were monitored for growth and survival for 1 year under standard culture conditions in two French production sites. Within-family genotype frequencies indicated that the two amylase genes were closely linked (c.

Marine water quality assessment using transplanted oyster larvae.

Active bio-monitoring in terms of biomarkers was attempted using Crassostrea gigas larvae produced in the laboratory and transplanted using special containers to two sites at the entrance (A) and inner part (P) of the harbour of Arcachon (French Atlantic Coast). The larvae were kept in the medium for 48 h. Their physiological status and their biomarker levels : acetylcholinesterase AChE, catalase CAT and glutathione S-transferase GST activities were determined together with metallothionein MT and Thiobarbituric Acid Reactive Substances TBARS concentrations.

Thermococcus atlanticus sp nov., a hyperthermophilic Archaeon isolated from a deep-sea hydrothermal vent in the Mid-Atlantic Ridge [corrected].

An extremely thermophilic archaeon, strain MA898, was isolated from a deep-sea hydrothermal vent on the Mid-Atlantic Ridge. This strain is a strictly anaerobic coccus of approximately 0.7-1.

Diversity of anaerobic heterotrophic thermophiles isolated from deep-sea hydrothermal vents of the Mid-Atlantic Ridge.

Abstract During the 'MARVEL' oceanographical cruise performed in September 1997, samples were collected from the deep-sea vents of hydrothermal sites on the Mid-Atlantic Ridge. Eighty-four thermophilic and hyperthermophilic heterotrophic microorganisms were isolated using different culture media containing cellobiose, xylan, starch, lipidic or proteic substrates. These isolates were obtained in anaerobic conditions, at 65 degrees C, 85 degrees C and 95 degrees C.

Microbial diversity in smoked salmon examined by a culture-independent molecular approach--a preliminary study.

Microbial biodiversity in sliced vacuum-packed cold smoked salmon was investigated using culture-independent molecular biology techniques. Sliced smoked salmon was stored for 25 days after being packed at 4 degrees C. DNA was extracted from sliced vacuum-packed cold smoked salmon.

Purification and characterization of an intracellular beta-glucosidase from a Candida sake strain isolated from fruit juices.

A yeast strain isolated in the laboratory from fruit juices was studied and classified as Candida sake. The strain produces an intracellular beta-glucosidase when grown with cellobiose as the carbon source. The enzyme was purified by ion-exchange chromatography and gel filtration.

Incorporation of microalgae sterols by scallop Pecten maximus (L.) larvae.

Changes in sterol composition of Pecten maximus larvae during the larval development stage with standard algal mixtures and unialgal diets were analysed. The sterol composition of four microalgae currently used in mollusc hatchery were also examined. Under standard algal conditions, the larvae quickly use the steryl ester from larvae reserves during the endotrophic and the mixotrophe phases.

Characterization of the maltooligosyl trehalose synthase from the thermophilic archaeon Sulfolobus acidocaldarius.

We report the molecular characterization and the detailed study of the recombinant maltooligosyl trehalose synthase mechanism from the thermoacidophilic archaeon Sulfolobus acidocaldarius. The mts gene encoding a maltooligosyl trehalose synthase was overexpressed in Escherichia coli using the T7-expression system. The purified recombinant enzyme exhibited optimum activity at 75 degrees C and pH 5 with citrate-phosphate buffer and retained 60% of residual activity after 72 h of incubation at 80 degrees C.

Cloning, expression, and characterization of DNA polymerase I from the hyperthermophilic archaea Thermococcus fumicolans.

The DNA polymerase I gene of a newly described deep-sea hydrothermal vent Archaea species, Thermococcus fumicolans, from IFREMERS's collection of hyperthermophiles has been cloned in Escherichia coli. As in Thermococcus litoralis, the gene is split by two intervening sequences (IVS) encoding inteins inserted in sites A and C of family B DNA polymerases. The entire DNA polymerase gene, containing both inteins, was expressed at 30 degrees C in E.

Amylase and trypsin responses to intake of dietary carbohydrate and protein depend on the developmental stage in sea bass (Dicentrarchus labrax) larvae.

Sea bass (Dicentrarchus labrax) larvae were fed from day 15 to day 35 with 4 isoenergetic formulated diets that varied in protein (30, 40, 50, 60%) and carbohydrate (37, 27, 17, 7%) content. The diets were designated as P30, P40, P50 and P60, respectively. Best growth and survival were noted for P50 larvae.

Maturation of the pancreatic and intestinal digestive functions in sea bass (Dicentrarchus labrax): effect of weaning with different protein sources.

The maturation of the digestive functions in sea bass (Dicentrarchus labrax) larvae was evaluated by the enzymatic profile of pancreas and intestine brush border membranes. Sea bass larvae were weaned at day 25 with three simplified diets different by their protein nature: 100% fish meal (FP), 100% casein mixture (CP) and 50% fish meal-50% casein mixture (CFP). The casein mixture contained 35% of hydrolysate.

Separation of major polar lipids in Pecten maximus by high-performance liquid chromatography and subsequent determination of their fatty acids using gas chromatography.

An easy method for the separation of major polar lipid classes by HPLC is described. Maximum resolution was achieved by an automated combination of a silica gel column and a diol column. Polar lipid analysis of the larvae and gonads of Pecten maximus showed the presence of a particular glycolipid especially rich in 22:6(n - 3) and the predominance of 20:4(n - 6) in the phosphatidylinositol.

Effect of the molecular form of dietary nitrogen supply in sea bass larvae: Response of pancreatic enzymes and intestinal peptidases.

Sea bass (Dicentrarchus labrax) larvae were weaned at day 25 with microparticulated diets in which 10% of the nitrogen supply had different molecular forms: amino acid mixture (SLAA), casein hydrolysate (SLH) or fish meal (SLP). The control group (LP) was fed live prey. No difference was observed in larval growth between the weaned groups, but the survival was significantly higher in the SLH group.

Development and response to a diet change of some digestive enzymes in sea bass (Dicentrarchus labrax) larvae.

Variations in some enzyme activities during larval development of sea bass fed live prey were investigated from hatching to day 40. Fluctuations in the enzyme specific activities (except for trypsin) occurred in three phases: initially a sharp increase until day 12, followed by a plateau and subsequently a decrease around day 23. Then activities remained constant until day 40.