Cycles de variations des elements nutritifs et du phytoplancton en baie de Douarnenez et dans les secteurs adjacents : importance du front cotier de l'Iroise

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Les virus des écosystèmes hydrothermaux océaniques profonds

En ligne à l'adresse suivante : http://www.biofutur.com/article.jsp?articleId=14687Parmi les paramètres physiques auxquels sont exposés les organismes vivants, la pression hydrostatique est probablement le moins étudié. Pourtant, l'essentiel du volume de la biosphère terrestre est soumis à des pressions élevées, dans les aquifères profonds, les réservoirs pétroliers, les couches profondes des sédiments océaniques La majorité des procaryotes terrestres vivrait ainsi en subsurface et serait soumise à des pressions hydrostatiques très élevées

Les thermopiézophiles ou la vie dans un autocuiseur !

En ligne à l'adresse suivante : http://www.biofutur.com/article.jsp?articleId=14687Parmi les paramètres physiques auxquels sont exposés les organismes vivants, la pression hydrostatique est probablement le moins étudié. Pourtant, l'essentiel du volume de la biosphère terrestre est soumis à des pressions élevées, dans les aquifères profonds, les réservoirs pétroliers, les couches profondes des sédiments océaniques La majorité des procaryotes terrestres vivrait ainsi en subsurface et serait soumise à des pressions hydrostatiques très élevées

Microbial diversity in Tunisian geothermal springs as detected by molecular and culture-based approaches

The original publication is available at www.springerlink.comInternational audienceProkaryotic diversities of 12 geothermal hot springs located in Northern, Central and Southern Tunisia were investigated by culture-based and molecular approaches. Enrichment cultures for both aerobic and anaerobic microorganisms were successfully obtained at temperatures ranging from 50 to 75 C. Fourteen strains including four novel species were cultivated and assigned to the phyla Firmicutes (9), Thermotogae (2), Betaproteobacteria (1), Synergistetes (1) and Bacteroidetes (1). Archaeal or universal oligonucleotide primer sets were used to generate 16S rRNA gene libraries. Representative groups included Proteobacteria, Firmicutes, Deinococcus-Thermus, Thermotogae, Synergistetes, Bacteroidetes, Aquificae, Chloroflexi, candidate division OP9 in addition to other yet unclassified strains. The archaeal library showed a low diversity of clone sequences belonging to the phyla Euryarchaeota and Crenarchaeota. Furthermore, we confirmed the occurrence of sulfate reducers and methanogens by amplification and sequencing of dissimilatory sulfite reductase (dsrAB) and methyl coenzyme M reductase a-subunit (mcrA) genes. Altogether, we discuss the diverse prokaryotic communities arising from the 12 geothermal hot springs studied and relate these findings

Marinitoga litoralis sp. nov., a thermophilic, heterotrophic bacterium isolated from a coastal thermal spring on Ile Saint-Paul, Southern Indian Ocean.

International audienceA novel thermophilic, anaerobic and organotrophic bacterium, designated strain MC3T, was isolated from a coastal thermal spring on Ile Saint-Paul in the Southern Indian Ocean. Cells of strain MC3T were motile rods, 0.8-1.0 microm wide and 1.0-2.4 microm long during exponential phase and up to 7.0 microm long during stationary phase. Strain MC3T was an anaerobic organotroph able to use diverse organic compounds. It was also able to reduce sulfur to sulfide. Growth was observed at temperatures ranging from 45 to 70 degrees C (optimum at 60 degrees C), between pH 5.5 and 7.5 (optimum at pH 6) and from 8 to 46 g NaCl l(-1) (optimum at 26 g l(-1)). The total G+C content of the genomic DNA was 26.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequence comparisons indicated that strain MC3T was affiliated with the genus Marinitoga within the order Thermotogales. It shared 94.4-95.7% 16S rRNA gene sequence similarity with strains of other Marinitoga species; Marinitoga hydrogenitolerans was found to be the most closely related organism. Based on the data from the phylogenetic analysis and the physiological properties of the novel isolate, strain MC3T should be classified as a representative of a novel species, for which the name Marinitoga litoralis sp. nov. is proposed; the type strain is MC3T (=DSM 21709T =JCM 15581T)

Presence of Hydrogenophilus thermoluteolus DNA in accretion ice in the subglacial Lake Vostok, Antarctica, assessed using rrs, cbb and hox

The 3561 m Vostok ice core sample originating from the subglacial Lake Vostok accretion (frozen lake water) ice with sediment inclusions was thoroughly studied by various means to confirm the presence of the thermophile bacterium Hydrogenophilus thermoluteolus reported earlier in the 3607 m accretion ice sample. PCR and molecular-phylogenetic analyses performed in two independent laboratories were made using different 16S rRNA gene ( rrs ) targeted primers. As a result, rrs -targeted PCR permitted to recover several very closely related clones with a small genetic distance to Hydrogenophilus thermoluteolus ( < 1%). In addition, RubisCO ( cbbL or rbcL ) and NiFe-Hydrogenase (hoxV or hupL ) targeted PCR have also allowed to recover sequences highly related to Hydrogenophilus thermoluteolus . All these results point to the presence of thermophilic chemoautotrophic microorganisms in Lake Vostok accretion ice. They presumably originate from deep faults in the bedrock cavity containing the lake in which episodes of seismotectonic activity would release debris along with microbial cells

Marinilactibacillus piezotolerans sp. nov., a novel marine lactic acid bacterium isolated from deep sub-seafloor sediment of the Nankai Trough.

A piezotolerant, mesophilic, marine lactic acid bacterium (strain LT20(T)) was isolated from a deep sub-seafloor sediment core collected at Nankai Trough, off the coast of Japan. Cells were Gram-positive, rod-shaped, non-sporulating and non-motile. The NaGl concentration range for growth was 0-120 gl(-1), with the optimum at 10-20 g l(-1). The temperature range for growth at PH 7.0 was 4-50 degreesC, with the optimum at 37-40 degreesC. The optimum pH for growth was 7.0-8.0. The optimum pressure for growth was 0.1 MPa with tolerance up to 30 MPa. The main cellular phospholipids were phosphatidylglycerols (25 %), diphosphatidylglycerols (34 %) and a group of compounds tentatively identified as ammonium-containing phosphatidylserines (32 %); phosphatidylethanolamines (9 %) were minor components. The fatty acid composition was dominated by side chains of 16:0, 14: 0 and 16: 1. The G +C content of the genomic DNA was 42 mol%. On the basis of 16S rRNA gene sequence analysis and the secondary structure of the V6 region, this organism was found to belong to the genus Marinilactibacillus and was closely related to Marinilactibacillus psychrotolerans M13-2(T) (99 %), Marinilactibacillus sp. strain MJYP.25.24 (99 %) and Alkalibacterium olivapovliticus strain ww2-SN4C (97 %). Despite the high similarity between their 16S rRNA gene sequences (99 %), the DNA-DNA hybridization levels were less than 20 %. On the basis of physiological and genetic characteristics, it is proposed that this organism be classified as a novel species, Marinilactibacillus piezatolerans sp. nov. The type strain is LT20(T) (= DSM 16108(T)=JCM 12337(T))

Pyrococcus yayanosii sp nov, an obligate piezophilic hyperthermophilic archaeon isolated from a deep-sea hydrothermal vent

UBO/IUEM; CNRS; Ifremer; ANR; EgideAn obligate piezophilic anaerobic hyperthermophilic archaeon, designated strain CH1(T), was isolated from a hydrothermal vent site named 'Ashadze', which is located on the Mid-Atlantic Ridge at a depth of 4100 m. Enrichment and isolation of the strain were carried out at 95 degrees C under a hydrostatic pressure of 42 MPa. Cells of strain CH1(T) were highly motile irregular cocci with a diameter of similar to 1-1.5 mu m. Growth was recorded at 80-108 degrees C (optimum 98 degrees C) and at pressures of 20-120 MPa (optimum 52 MPa). No growth was observed under atmospheric pressures at 60-110 degrees C. Growth was observed at pH 6.0-9.5 (optimum 7.5-8.0) and in 2.5-5.5 % (w/v) NaCl (optimum 3.5%). Strain CH1(T) was strictly anaerobic and grew on complex proteinaceous substrates, such as yeast extract, Peptone, and casein, as well as on sucrose, starch, chitin, pyruvate, acetate and glycerol without electron acceptors. The G+C content of the genomic DNA was 49.0 +/- 0.5 mol%. Analysis of 16S rRNA gene sequences revealed that strain CH1(T) belongs to the genus Pyrococcus. Based on its physiological properties and similarity levels between ribosomal proteins, strain CH1(T) represents a novel species, for which the name Pyrococcus yayanosii sp. nov. is proposed. The type strain is CH1(T) (=JCM 16557). This strain is also available by request from the Souchotheque de Bretagne (catalogue LMBE) culture collection (collection no. 3310)