Isolation and characterization of Halothermothrix orenii gen. nov., sp. nov., a halophilic, thermophilic, fermentative, strictly anaerobic bacterium

The occurrence of thermophilic, halophilic anaerobic bacteria in the sediment of a Tunisian salted lake was tested in samples collected at 20-cm intervals down to a depth of 1.20 m. A long rod, present only in the 40-to 60-cm layer, was isolated at 60°C in a medium containing 100 g of NaCl per liter and designated strain H168. This strain produced acetate, ethanol, H2, and CO2 from glucose metabolism. Fructose, xylose, ribose, cellobiose, and starch were also oxidized. The optimum temperature for growth was 60°C. No growth was obtained at 42 or 70°C. Strain H168 grew optimally in NaCl concentrations ranging from 50 to 100 g per liter, with the upper and lower limits of growth around 200 and 40 g per liter, respectively. The G+C ratio of the DNA was 39.6 mol %. Although halophilic, moderately thermophilic bacteria have been characterized among anaerobes, particularly within methanogens, strain H168 is the first true thermophilic (growing above 60°C) halophilic anaerobic bacterium described so far. The phylogeny, physiology, morphology, lipid content, and high G+C content of strain H168 are sufficiently different from those of genera belonging to the family Haloanaerobiaceae to justify the definition of a new genus

Structure, rheology, and copper-complexation of a hyaluronan-like exopolysaccharide from Vibrio

MO245 exopolysaccharide (EPS) was produced in laboratory conditions from Vibrio genus microorganism isolated from bacterial mats found in Moorea Island. Its structure consists of a linear tetrasaccharide repeating unit →4)-β-D-GlcpA-(1→4)-α-D-GalpNAc-(1→3)-β-D-GlcpNAc-(1→4)-β-D-GlcpA-(1→ containing covalently-linked 5% of glucose, galactose, and rhamnose, determined by methylation analyses and NMR spectroscopy. The molecular weight, radius of gyration (Rg) and intrinsic viscosity, [η], determined by gel permeation chromatography with light scattering and viscosity detection, were 513 ± 4 kDa (PDI, 1.42 ± 0.01), 6.7 ± 0.3 dl/g and 56 ± 0.3 nm respectively. The chelation of the EPS with copper divalent ions leads to the instantaneous formation of gels. The structural similitude proposed, based in an equal ratio of GlcA to N-acetylated sugars and in the same type of glyosidic linkages present in the repeating unit (alternated 1→3 and 1→4 linkages), is translated into analogous physicochemical properties: MO245 EPS is a flexible polyelectrolyte, with scaling exponents similar to that described for HA. This similitude opens opportunities in future drug delivery, tissue engineering, and cosmetic applications.publishe

Les bactéries des sources hydrothermales profondes a l’origine de nouvelles molécules bioactives ?

La découverte des sources hydrothermales profondes mais de manière plus générale l’étude de milieux extrêmes, ont ouvert la voie à la mise en évidence de microorganismes bien adaptés à ces conditions atypiques et capables de synthétiser de molécules d’intérêt biotechnologique . Des recherches réalisées durant de nombreuses années ont permis la caractérisation d’exopolysaccharides innovants dont des applications sont maintenant envisagées dans différents secteurs industriels tels l’agro-alimentaire, la cosmétique et l’environnement mais surtout dans le domaine de la santé, s’agissant de l’oncologie, du cardio-vasculaire et de la régénération dermique.In the course of the discovery of novel polysaccharides of biotechnological interest, it is now widely accepted that extremophilic microorganisms will provide a valuable resource not only for exploitation in novel biotechnological processes but also as models for investigating how biomolecules are stabilized when subjected to extreme conditions. Deep-sea hydrothermal vents offer a new source of a variety of  fascinating microorganisms well adapted to these extreme environments. Over the past 15 years, an increasing number of new genera and species of both hyperthermophilic and mesophilic bacteria have been isolated from these deep-sea hydrothermal vents. This new bacterial diversity include strains able to produce under laboratory conditions, novel molecules such as polymers including exopolysaccharides and poly beta hydroxyalkanoates and other bioactive molecules

Chapitre X. Exopolysaccharides bactériens et bioremédiation des métaux : contribution du milieu marin

1. Introduction La protection de l’environnement est un problème majeur pour notre qualité de vie et c’est aussi, et surtout, un problème de santé humaine. Malheureusement, les pollutions de toute nature font partie de notre quotidien : matériaux plastiques non dégradables, utilisation abusive de pesticides, herbicides, fongicides et autres contaminants organiques, contaminations accidentelles de nappes phréatiques, sols, sédiments, milieux aquatiques et effluents industriels par des produits..

La biocorrosion. Processus caractéristiques et moyens d’études

In contrast to the situation of a few years ago, the phenomenon of microbiologically induced corrosion is now generally accepted as being one of a number of mechanisms whereby corrosion occurs. A considerable amount of multi-disciplinary effort has been expended to determine the extent of the problem and to understand the phenomenon. Microbial corrosion refers to the degradation of metallic or non metallic structures resulting from the presence and the activity of a variety of organisms on the surfaces. Although, in many cases, microbial corrosion is closely associated with biofouling phenomena, the area in which it causes most damages concern the deterioration of metallic structures in soils and sediments with the well-known sulphate-reducing bacteria

Les ressources marines de la Polynésie française : applications en matière de biotechnologie

1. Le contexte polynésien La Polynésie française se situe en fin de gradient de la biodiversité indopacifique et s’étend sur 20° de latitude (entre 7° et 27°S., soit plus de 2 000 km) des latitudes équatoriales à subtropicales et entre 135° et 155° de longitude ouest. Les îles se répartissent en cinq archipels : Société, Tuamotu, Gambier, Australes et Marquises. On reconnaît classiquement deux grands types de formations récifales : les îles hautes volcaniques ceinturées par un lagon peu profo..

Etude structurale des polysaccharides pariétaux de l'algue rouge Asparagopsis armata (Bonnemaisoniales)

La caractérisation structurale des polysaccharides pariétaux hydrosolubles de l'algue rouge Asparagopsis armata (Bonnemaisoniales) est réalisée, montrant que la chaîne saccharidique principale est constituée d'un enchaînement régulier d'unités 3-f-D-galactopyranose et 4-a-DJL-galactopyranose, plus ou moins substituées par des groupements sulfate et des oses terminaux. La nature hybride de ces polysaccharides (présence concomitante d'unités 4-a-galactopyranose de configuration D et L) est démontrée, de même que la présence de substituants (groupements pyruvate et méthyle) et d'oses terminaux (xyloses et galactoses éventuellement sulfatés). Il s'agit donc de polysaccharides hybrides constitués d' agarocolloïdes (agaroïdes) et de carraghénanes de différentes familles (xi- et pi-carraghénanes d'une part, et gamma- et psi-carraghénanes polysulfatés de manière hétérogène d'autre part), corroborant ainsi l'hypothèse de polysaccharides hétérogènes au niveau structural.The structural analysis of the water-soluble cell-wall polysaccharides from the red seaweed Asparagopsis armata (Bonnemaisoniaceae) was reali7ed, revealing a linear backbone built up of alternating 3-iinked-fl-D-galactopyranosyi and 4-linked-a-DIL-galactopyranosyl residues that might carry substituents such as sulfate ester or sugar side=chains. The presence of 4-linked residues belonging to the both D- and L-sertes demonstrated that these polysaccharides are complex hybrid galactans. In addition, presence of substituants (pyruvate or methyl groups) as well as of side-chains sugar (xylose or galactose, which carry sulfate ester groups) was determine. Thus, these polysaccharides were identified as complex DL-galactan hybrids with mixed carrageenan (belonging on one band to the Mi- and pi-family, and on the other band to the gamma- and psi-family sulfated in an heterogeneous way), and agar backbone structure.BREST-BU Droit-Sciences-Sports (290192103) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF