Balneola alkaliphila sp. nov., a marine bacterium isolated from the Mediterranean Sea

En libre-accès sur Archimer : http://archimer.ifremer.fr/doc/2008/publication-5292.pdfInternational audienceA novel aerobic, Gram-negative bacterium, designated strain CM41_14b(T), was isolated from surface waters in the coastal north-western Mediterranean Sea. Cells were non-motile, straight rods, 2.6 microm long and 0.7 microm wide and formed pale-orange colonies on marine agar medium. The G+C content of the genomic DNA was 39 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence placed the strain within the genus Balneola (phylum Bacteroidetes). On the basis of 16S rRNA gene sequence comparisons, and physiological and biochemical characteristics, the isolate represents a novel species for which the name Balneola alkaliphila sp. nov. is proposed. The type strain is CM41_14b(T) (=DSM 19538(T)=CIP 109603(T)=OOB 103(T))

Thalassobaculum salexigens sp. nov., a new member of the family Rhodospirillaceae from the NW Mediterranean Sea, and emended description of the genus Thalassobaculum

En libre-accès sur Archimer : http://archimer.ifremer.fr/doc/00001/11201/7846.pdfInternational audienceA novel Gram-negative bacteria, named CZ41_10a(T), was isolated from coastal surface waters of the north-western Mediterranean Sea. Cells were motile, pleomorphic rods, 1.6 mum long and 0.7 mum wide and formed cream colonies on marine agar medium. The G+C content of the genomic DNA was 65 mol%. Phylogenetic analysis of 16S rRNA gene sequences placed the new isolate in the genus Thalassobaculum, a member of the family Rhodospirillaceae, class Alphaproteobacteria. Unlike Thalassobaculum litoreum CL-GR58(T), its closest relative, strain CZ41_10a(T) was unable to grow anaerobically and did not exhibit nitrate reductase activity. On the basis of DNA-DNA hybridization, fatty acid content and physiological and biochemical characteristics, this isolate represents a novel species for which the name Thalassobaculum salexigens sp. nov. is proposed. The type strain is CZ41_10a(T) (=DSM 19539(T)=CIP 109604(T)=MOLA [corrected] 84(T)). An emended description of the genus Thalassobaculum is also given

Application of ToF-SIMS for sulfur isotopic fractionation in sulfide phases of iron corrosion layers: determination of bacterial impact on the formation of these phases

International audienceTo a better understanding of the iron corrosion mechanisms, it is crucial to elucidate the role of bacteria. Thus, in order to have a diagnosis of the action of bacteria in the iron corrosion, the objective of this study is to determine by ToF-SIMS the isotopic sulfur fractionation δ 34 S in iron sulfides of (sub)micrometric size located in the corrosion product layers of the ferrous objects corroded in anoxic soils and marine environment. These iron sulfides may have two origins: an abiotic origin resulting in the dissolution/reprecipitation of sulfides from the surrounding medium (for example from pyrite in a soil) or a biotic origin by the action of the sulfate-reducing bacteria that reduce sulfate ions into sulfides leading to the formation of iron sulfides with ferrous ions issued from the aqueous dissolution of metal iron. A difference in the isotopic sulfur fractionation δ 34 S in the sulfur phases according to the abiotic or biotic origin of these phases is reported in the literature. Thus in this study, the isotopic sulfur fractionation δ 34 S in the iron sulfides formed in the corrosion product layers of iron was determined to identify the formation origin of these phases and the role of bacteria in the iron corrosion. After characterization of the distribution of the different iron sulfides within the layers (optical microscopy, SEM-EDS, μRaman spectroscopy), the local isotopic fractionation of sulfur is measured by the imaging and spectroscopy ToF-SIMS technique. Some important results have been obtained. First of all, the reproducibility and the accuracy of the method were established by the choice and the validation of a hydrothermal pyrite sample calibrated relatively to the international sulfur isotopic standard Canon Diablo Troilite. Secondly, it was observed that there was no or little variation in the isotopic sulfur fractionation δ 34 S with the degree of oxidation of sulfur. Finally, a noticeable difference in the isotopic sulfur fractionation δ 34 S between iron sulfides formed in laboratory under abiotic or biotic conditions was evidenced: δ 34 S is close to 0 in abiotic conditions whereas in biotic conditions it is shifted from 0 with values up to up to some tens per mil. These first results being promising, the study is actually in progress to determine the formation origin (abiotic/biotic) of the Fe-S present in the corrosion product layers of natural systems of iron corrosion, from soils, subaquatic and marine environments

Haliea rubra sp. nov., a member of the Gammaproteobacteria from the Mediterranean Sea

International audienceA novel aerobic, Gram-negative bacterium, designated strain CM41_15a(T), was isolated from the surface of coastal waters of the north-western Mediterranean Sea. Cells were non-motile straight rods that formed red colonies on marine agar medium. The G+C content of the genomic DNA was 65 mol %. Phylogenetic analysis of the 16S rRNA gene sequence placed the strain in the genus Haliea within the class Gammaproteobacteria. On the basis of the 16S rRNA gene sequence comparison and physiological and biochemical characteristics, strain CM41_15a(T) represents a novel species, for which the name Haliea rubra sp. nov. is proposed. The type strain is CM41_15a(T) (=DSM 19751(T)=CIP 109758(T)=MOLA 104(T))

Eionea nigra gen. nov., sp. nov., a gammaproteobacterium from the Mediterranean Sea

International audienceA novel aerobic, gram-negative bacterial strain, designated 17X/A02/237(T), was isolated from waters of the coastal north-western Mediterranean Sea. Cells were motile straight rods and formed dark-grey colonies on marine agar medium. Strain 17X/A02/237(T) contained ubiquinone Q-8 and its major fatty acids were C(16 : 1)ω7c and/or iso-C(15 : 0) 2-OH, C(18 : 1)ω7c, C(16 : 0), C(18 : 0) and C(10 : 0) 3-OH. The G+C content of the genomic DNA was 47.5 mol%. Phylogenetic analysis of the 16S rRNA gene sequence placed the strain in the class Gammaproteobacteria. Based on 16S rRNA gene sequence data, as well as physiological and biochemical characteristics, this isolate represents a novel species of a new genus, for which the name of Eionea nigra gen. nov., sp. nov. is proposed. The type strain is 17X/A02/237(T) ( = DSM 19752(T) = CIP 109759(T) = MOLA 288(T))

Nisaea denitrificans gen.nov., sp.nov. and Nisaea nitrireducens sp. nov., two novel members of the class Alphaproteobacteria from the Mediterranean Sea

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Microbial Diversity at Iron-Clay Interfaces after 10 Years of Interaction Inside a Deep Argillite Geological Formation (Tournemire, France)

International audienceIn the context of a geological disposal of radioactive waste in clayey formations, the consequences of microbial activity are of concern regarding the corrosion of metallic components. The purpose of the present work was to characterize the microbial diversity that may have impacted corrosion processes at the interface between re-compacted argillite and steel coupons after 10 years of interaction inside the Toarcian argillite layer in Tournemire (France) under in situ conditions. Several types of steel coupons were introduced in 1999 in two boreholes (so-called CR6 and CR8) drilled in the geological formation and filled with re-compacted argillite. CR6 borehole was drilled horizontally from a century-old railway tunnel and coupons were placed in the undisturbed argillite. CR8 borehole was drilled vertically under the tunnel, in conditions influenced by the draining of the Cernon fault water. CR6 and CR8 boreholes were overcored 10 years later and steel coupons as well as re-compacted argillite samples were analyzed separately. The characterization of their microbial diversity was carried out using culture media and molecular methods using 16S rRNA genes cloning. Data resulting from both approaches were complementary. Isolates and clone sequences were affiliated to only 3 bacterial phyla Firmicutes, Actinobacteria and Proteobacteria. The biodiversities differed depending on the steel type and the borehole considered, indicating the influence of both iron-clay interactions and in situ environmental conditions. This analysis has highlighted the presence of sulphate-reducing bacteria, iron-reducing bacteria and isolates capable to develop at high temperatures. These microorganisms can grow at the interfaces between materials in a very short period of time compared with planned durations of disposal. Thus, these results should be considered to assess the consequences of microbial activities on the evolution of the metallic components like overpacks. © 2013 Copyright Taylor and Francis Group, LLC

Microbial diversity of the 180 million-year-old Toarcian argillite from Tournemire, France

International audienceEven though the microbiology of various subsurface environments has been investigated for more than 30 a, the microbial diversity of deep argillaceous media is still poorly known. In the context of radioactive waste disposal in clayey formations, the consequence of microbial activity is of concern regarding e.g. the corrosion of metallic components. The purpose of the present work was to characterise the cultivable microbial diversity of different zones of the Toarcian argillite of Tournemire (France) as a preliminary indication regarding the potential of development of microbes in such subterrestrial environments. Cores were drilled in the Excavation Damaged Zone (EDZ) and in the deeper undisturbed zone of the argillite layer, as well as in a zone intersected by a geological fault. Samples from the wall of the drift were also collected. Microorganisms were cultivated from all samples, but the biodiversity differed depending mainly on the O 2 and moisture content. Aerobic bacteria were identified on the wall, in the EDZ and in the wet faulted area, whereas SO 4-reducing bacteria were isolated from the wet faulted area only. Anaerobic heterotrophs were cultivated from all zones. One hundred and twelve isolates were identified. Small ribosomal subunit gene sequences showed that bacteria of the undisturbed zone were affiliated to three genera only, whereas the three other sampled zones harbour more diverse microflora, including isolates closely related to taxons characterized from subsurface, deep marine and polar environments. © 2011