Tungsten-enhanced growth of Methanosphaera stadtmanae

Background: The methanogenic Archaea Methanosphaera stadtmanae has been detected in the human gut microbiota by both culture and culture-independent methods. Its growth reaches an exponential phase after 5 to 7-day culture in medium 322 (10% vol). Our recent successful isolation of Methanomassiliicoccus luminyensis, a tungstate-selenite-requiring Archaea sharing similar metabolism characteristics with M. stadtmanae prompted us to study the effects of tungsten and selenium on M. stadtmanae growth.Findings: Addition of 0.2 mg/L sodium tungstate to medium 322 yielded, 48 hours after inoculation, a growth rate equivalent to that obtained after 6 days with control culture as measured by methane monitoring and optical density measurement. Addition of 50 μg/mL sodium selenate had no effect on M. stadtmanae growth. Quantitative real-time PCRs targeting the M. stadtmanae 16S rRNA confirmed these data.Conclusions: These data provide new information regarding the poorly known nutritional requirements of the human gut colonizing organisms M. stadtmanae. Adding sodium tungstate to basal medium may facilitate phenotypic characterization of this organism and additionally aid the isolation of new Archaeafrom complex host microbiota

Peptide and amino acid oxidation in the presence of thiosulfate by members of the genus Thermoanaerobacter

#Thermoanaerobacter brockii, #T. ethanolicus, #T. thermohydrosulfuricus, #T. finnii, and #Thermoanaerobacter strain SEBR 5268 (an isolate from an oil-producting well) were studied for their ability to oxidize proteinaceous compounds that included gelatin, peptides, and casamino acids. All bacteria tested used peptides and amino acids, but only slightly. However, in the presence of thiosulfate all the #Thermoanaerobacter species showed a substantial improvement in growth and/or the production of acetate, isovalerate, isobutyrate, and sulfide. Propionate was a minor product of peptide or amino acid oxidation. The reduction of thiosulfate during growth on peptides by members of the #Thermoanaerobacter$ species is a trait that closely resembles that of archaeal hyperthermophiles during growth on peptides and amino acids with elemental sulfur as electron acceptor. (Résumé d'auteur

Effect of thiosulphate as electron acceptor on glucose and xylose oxidation by Thermoanaerobacter finnii and Thermoanaerobacter sp. isolated from oil field water

#Thermoanaerobacter finnii fermente le glucose et le xylose en lactate, acétate, H2, CO2 et éthanol qui est le produit majeur du métabolisme. Une autre bactérie du genre #Thermoanaerobacter isolée d'une eau de gisement pétrolier produit des quantités aussi importantes d'éthanol que de lactate à partir de ces sucres. L'oxydation du glucose et du xylose par ces deux micro-organismes est complètement modifiée en présence de thiosulfate puisque, dans ces conditions, l'acétate devient le produit majeur du métabolisme des sucres. Cette modification du métabolisme amène à de meilleurs rendements cellulaires et à un meilleur taux de croissance bactérienne lorsque le thiosulfate est utilisé comme accepteur d'électrons. Une plus grande production d'acétate en présence de thiosulfate indique que les bactéries testées récupèrent plus d'énergie des phosphorylations liées au substrat. Ces modifications observées sur le métabolisme des sucres en présence de thiosulfate nous amènent à tenir compte plus précisément du rôle que peut jouer cet accepteur d'électrons dans l'oxydation de la matière organique dans les sources chaudes riches en sulfate sulfuré ou les eaux de gisements pétroliers. (Résumé d'auteur

Caractérisation des bactéries cadmium-résistantes isolées de sols pollués en Algérie et évaluation de l’élimination du cadmium en utilisant des cellules libres ou immobilisées

La pollution des sols par les métaux lourds est un problème particulièrement préoccupant du fait de leur toxicité et de leur non biodégradabilité. Dans ces environnements, les bactéries développent divers mécanismes de résistance qui leurs confèrent la capacité à accumuler ces métaux. Dans cette étude, vingt-trois bactéries cadmium-résistantes ont été isolées de trois sols algériens et ont été caractérisées. Deux isolats (YL-SS8, YL-SS3), hautement résistants au cadmium, ont été sélectionnés et identifiés par séquençage du gène de l’ARNr 16S, puis testés pour leur capacité à capturer les ions cadmium. Les résultats ont révélé que les bactéries caractérisées appartenaient à neuf familles et dix genres, tandis que les deux souches les plus résistantes sélectionnées, ont été identifiées comme Bacillus infantis et Pseudomonas fluorescens. Les concentrations minimales inhibitrices ou CMI oscillaient entre 500 μg.mL-1 et 1100 μg.mL-1. Les souches YL-SS8 etYL-SS3 ont montré les CMI les plus importantes, de l’ordre de 1100 μg.mL-1 et 900 μg.mL-1 respectivement. Les cellules libres vivantes de B. infantis ont prélevé environ 90 μg.mL-1 de cadmium, alors que celles de P. fluorescens ont capturé 81 μg.mL-1 après 24 heures de contact. Dans le même temps, les cellules immobilisées ont accumulé des concentrations en cadmium légèrement plus importantes avec des valeurs respectives de 93 μg.mL- 1 et 85 μg.mL-1. En raison de leur forte résistance et de leur importante capacité d’accumulation du cadmium, les deux isolats bactériens pourraient être exploités pour l’assainissement biotechnologique du cadmium dans les sols contaminés par les métaux lourds.Soil pollution by heavy metals is one of the most important problems around the world. Microorganisms in these environments develop various mechanisms of resistance and become able to accumulate these metals. In this study, twenty-three cadmium-resistant bacteria were isolated from three soils and characterized. Two of them (YL-SS8, YL-SS3), highly cadmium-resistant, were selected and identified by the sequencing of the 16S rRNA gene, then tested for their ability to remove cadmium ions. The results revealed that the characterized bacteria belonged to nine families and ten genera, while the most resistant are authentically identified as Bacillus infantis and Pseudomonas fluorescens. The MIC of bacteria ranged from 500 µg.mL-1 to 1100 μg.mL-1, Bacillus infantis and Pseudomonas fluorescens showed MIC of the order of 1100 μg.mL-1 and 900 μg.mL-1respectively. The free living cells of B. infantis accumulated about 90 μg.mL-1 of cadmium, whereas those of P. fluorescens 81 μg.mL-1 after 24 hours of contact. During the same time, the immobilized cells accumulated quantities slightly better with respective values of 93 μg.mL-1and 85 μg.mL-1. Due to their strong resistance and high cadmium removal capacity, the two bacterial isolates could be exploited for biotechnological remediation of cadmium and other heavy metals from contaminated soils

Melghirimyces algeriensis gen. nov., sp. nov., a member of the family Thermoactinomycetaceae, isolated from a salt lake.

A novel filamentous bacterium, designated NariEX(T), was isolated from soil collected from Chott Melghir salt lake, which is located in the south-east of Algeria. The strain was an aerobic, halotolerant, thermotolerant, Gram-positive bacterium that was able to grow in NaCl concentrations up to 21% (w/v), at 37-60 °C and at pH 5.0-9.5. The major fatty acids were iso- and anteiso-C(15:0). The DNA G+C content was 47.3 mol%. The major menaquinone was MK-7, but MK-6 and MK-8 were also present. The polar lipid profile consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylmonomethylethanolamine (methyl-PE). Results of molecular and phenotypic analysis led to the description of the strain as a new member of the family Thermoactinomycetaceae. The isolate was distinct from members of recognized genera of this family by morphological, biochemical and chemotaxonomic characteristics. Strain NariEX(T) showed 16S rRNA gene sequence similarities of 95.38 and 94.28% with the type strains of Desmospora activa and Kroppenstedtia eburnea, respectively, but differed from both type strains in its sugars, polar lipids and in the presence of methyl-PE. On the basis of physiological and phylogenetic data, strain NariEX(T) represents a novel species of a new genus of the family Thermoactinomycetaceae for which the name Melghirimyces algeriensis gen. nov., sp. nov. is proposed. The type strain of Melghirimyces algeriensis, the type species of the genus, is NariEX(T) (=DSM 45474(T)=CCUG 59620(T))

Melghirimyces algeriensis gen. nov., sp. nov., a member of the family Thermoactinomycetaceae, isolated from a salt lake.

A novel filamentous bacterium, designated NariEX(T), was isolated from soil collected from Chott Melghir salt lake, which is located in the south-east of Algeria. The strain was an aerobic, halotolerant, thermotolerant, Gram-positive bacterium that was able to grow in NaCl concentrations up to 21% (w/v), at 37-60 °C and at pH 5.0-9.5. The major fatty acids were iso- and anteiso-C(15:0). The DNA G+C content was 47.3 mol%. The major menaquinone was MK-7, but MK-6 and MK-8 were also present. The polar lipid profile consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylmonomethylethanolamine (methyl-PE). Results of molecular and phenotypic analysis led to the description of the strain as a new member of the family Thermoactinomycetaceae. The isolate was distinct from members of recognized genera of this family by morphological, biochemical and chemotaxonomic characteristics. Strain NariEX(T) showed 16S rRNA gene sequence similarities of 95.38 and 94.28% with the type strains of Desmospora activa and Kroppenstedtia eburnea, respectively, but differed from both type strains in its sugars, polar lipids and in the presence of methyl-PE. On the basis of physiological and phylogenetic data, strain NariEX(T) represents a novel species of a new genus of the family Thermoactinomycetaceae for which the name Melghirimyces algeriensis gen. nov., sp. nov. is proposed. The type strain of Melghirimyces algeriensis, the type species of the genus, is NariEX(T) (=DSM 45474(T)=CCUG 59620(T))

Identification of thiosulfate- and sulfur -reducing bacteria unable to reduce sulfate in ricefield soils

Eighteen strains of anaerobic thiosulfate-reducing bacteria unable to use sulfate as electron acceptor (TSRnSR) were isolated from four ricefield soils originating from France and the Philippines, using peptides as energy sources, H2 as electron donor, thiosulfate as electron acceptors, and four enrichment methods to vary the selection pressure. They were strict proteolytic asaccharolytic anaerobes producing H2S when grown on thiosulfate + H2. They exhibited the same RFLP profile (11 restriction enzymes tested). Partial sequencing of the 16S rDNA showed that they belonged to the genus Clostridium and were phylogenetically related to C. subterminale. DNA-DNA hybridization of a representative strain with the closest C. subterminale strain (DSM 6970T) yielded a value of 68.9%. Previous counts of TSRnSR in ricefield soils, their identification as Clostridium strains, and the known ubiquity of this genus in such soils indicate that TSRnSR may play a significant role in S cycling in some wetland soils. (Résumé d'auteur

Studies on the Biodiversity of Halophilic Microorganisms Isolated from El-Djerid Salt Lake (Tunisia) under Aerobic Conditions

Bacterial and archaeal aerobic communities were recovered from sediments from the shallow El-Djerid salt lake in Tunisia, and their salinity gradient distribution was established. Six samples for physicochemical and microbiological analyses were obtained from 6 saline sites in the lake for physico-chemical and microbiological analyses. All samples studied were considered hypersaline with NaCl concentration ranging from 150 to 260 g/L. A specific halophilic microbial community was recovered from each site, and characterization of isolated microorganisms was performed via both phenotypic and phylogenetic approaches. Only one extreme halophilic organism, domain Archaea, was isolated from site 4 only, whereas organisms in the domain Bacteria were recovered from the five remaining sampling sites that contained up to 250 g/L NaCl. Members of the domain Bacteria belonged to genera Salicola, Pontibacillus, Halomonas, Marinococcus, and Halobacillus, whereas the only member of domain Archaea isolated belonged to the genus Halorubrum. The results of this study are discussed in terms of the ecological significance of these microorganisms in the breakdown of organic matter in Lake El-Djerid and their potential for industry applications