Paenibacillus marinum sp. nov., a thermophilic xylanolytic bacterium isolated from a marine hot spring in Tunisia.

Among a large collection of Tunisian hot springs bacterial isolates a bacterial strain, THE22(T) , with xylanolytic properties was identified. The bacterium was isolated from a natural hot spring "Ain Echefa" at Mediteranean sea (Korbous, North-Eastern Tunisia). The novel strain was Gram positive, spore-forming, rod-shaped, facultatively anaerobic and grew optimally under conditions of 55 °C, 1% (w/v) NaCl and pH 7-8. The 16S rRNA gene sequence analysis showed that strain THE22(T) fell within the radiation of the cluster comprising Paenibacillus species with Paenibacillus phyllosphaerae PALXIL04(T) as the closest phylogenetic neighbour (95.8%). The predominant components in the fatty methyl ester profile were iso-C16:0 (34.46%), C16:0 (19.64%), anteiso-C15:0 (19.18%) and anteiso-C17:0 (18.11%). The major respiratory quinone was menaquinone-7 (MK-7). The diamino acid found in the cell-wall peptidoglycan was meso-diaminopimelic acid. The base composition of DNA was 56 mol%. Based on the polyphasic taxonomic data, strain THE-22(T) (=DSM 18499(T) = LMG 23758(T) ) was recognized as a novel species within the genus Paenibacillus. The name Paenibacillus marinum sp. nov. is proposed.

Characterization of Deinococcus sahariens sp. nov., a radiation-resistant bacterium isolated from a Saharan hot spring.

An ultraviolet-radiation-resistant, Gram-positive, orange-pigmented, thermophilic and strictly aerobic cocci was isolated from Saharan water hot spring in Tunisia. The newly isolated bacterium, designated HAN-23(T), was identified based on polyphasic taxonomy including genotypic, phenotypic and chemotaxonomic characterization. Phylogenetic analysis based on 16S rRNA gene sequences placed this strain within Deinococcus genus. However, strain HAN-23(T) is different from recognized species of the genus Deinococcus, showing less than 94.0% similarity values to its closest relatives. The predominant cellular fatty acids determined by gas chromatography were iso-C(15:0), iso-C(17:0) and iso C(17:1) ω9c. The major respiratory quinone was MK-8. The DNA G + C content was 66.9 mol%. DNA-DNA hybridization measurements revealed low DNA relatedness (6%) between the novel isolate and its closest neighbor, the type strain Deinococcus geothermalis DSM 11300. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, strain HAN-23(T) represents a novel species of the genus Deinococcus, for which the name Deinococcus sahariens sp. nov. is proposed, the type strain being HAN-23(T) (=DSM 18496(T); LMG 23756(T)).

A thermostable feruloyl-esterase from the hemicellulolytic bacterium Thermobacillus xylanilyticus releases phenolic acids from non-pretreated plant cell walls.

A gene (Tx-est1) encoding a thermostable feruloyl-esterase was isolated from the genome of the gram-positive hemicellulolytic thermophilic bacterium Thermobacillus xylanilyticus. This gene contains an open reading frame of 1,020 bp encoding a protein with molecular mass of 37.4 kDa, similar to feruloyl-esterases from cellulolytic bacteria and fungi. The recombinant enzyme Tx-Est1 was expressed and produced in Escherichia coli. Tx-Est1 contains the conserved putative lipase residues Ser 202, Asp 287, and His 322 which act as catalytic triad in its C-terminus part. Purified Tx-Est1 was active against phenolic acid derivatives and stable at high temperatures. Optimal activity was observed at 65 °C and the optimal pH was around 8.5. The kinetic parameters of the esterase were determined on various substrates. The enzyme displayed activity against methyl esters of hydrocinnamic acids and feruloylated arabino-xylotetraose, exhibiting high specificity and affinity for the latter. Our results showed that Tx-Est1 is a thermostable feruloyl-esterase which could be useful to hydrolyze arabinoxylans from graminaceous plant cell walls as the enzyme is able to release phenolic acids from a lignocellulose biomass.

Caldimonas hydrothermale sp. nov., a novel thermophilic bacterium isolated from Roman hot bath in south Tunisia.

A polyphasic approach was used to characterize a bacterium, HAN-85(T), isolated from thermal water in natural thermal spring at Tozeur, an oasis in southwest Tunisia. The novel isolate was thermophilic, strictly aerobic and amylolytic bacterium, which stained Gram negative. Cells were short rods motile by means of a single polar flagellum. Their optimum temperature and pH required for growth were 55 degrees C and pH 7, respectively. Comparative 16S rRNA gene sequence analyses showed that strain HAN-85(T) belonged to the genus Caldimonas, with highest sequence similarity to the type strains Caldimonas manganoxidans and Caldimonas taiwanensis. DNA-DNA hybridization measurements revealed low DNA relatedness (35.2-44.5%) between the novel isolate and its closest relative, C. manganoxidans. The major cellular fatty acid components were 16:0, 17:0 cyclo and summed feature 3. The DNA G+C content was 68.3 mol%. Taken together, the results of DNA-DNA hybridization, fatty acids profile, physiological tests and biochemical analyses have allowed the genotypic and phenotypic differentiation of the isolate from currently recognized Caldimonas species. Therefore, we suggest that this isolate is a novel species within the genus Caldimonas and propose that it should be named Caldimonas hydrothermale sp. nov. The type strain is HAN-85(T) (=DSM 18497(T) =LMG 23755(T)).

Biochemical and phylogenetic characterization of a novel terrestrial hyperthermophilic archaeon pertaining to the genus Pyrococcus from an Algerian hydrothermal hot spring.

A hyperthermophilic anaerobic archeon, strain HT3, was isolated from hydrothermal hot spring in Northeast Algeria. The strain is a regular coccus, highly motile, obligatory anaerobic, heterotrophic. It utilizes proteinaceous complex media (peptone, tryptone or yeast extract). Sulfur is reduced to Hydrogen sulfide and enhances growth. It shares with other Pyrococcus species the heterotrophic mode of nutrition, the hyperthermophily, the ability to utilize amino acids as sole carbon and nitrogen sources and the ether lipid composition. The optimal growth occurs at 80-85 degrees C, pH 7.5 and 1.5% NaCl. The G + C content was 43 mol%. Considering its morphology, physiological properties, nutritional features and phylogenetic analyses based on 16S rRNA gene sequencing, this strain is described as a new terrestrial isolate pertaining to the genus Pyrococcus.

Synthesis and characterization of dehydrogenation polymers in Gluconacetobacter xylinus cellulose and cellulose/pectin composite.

To mimic the lignin polymerization process, mats of bacterial cellulose and of a pectin/cellulose composite were used as a host matrix for in vitro polymerization of coniferyl alcohol. A diffusion cell was used to allow the diffusion of both hydrogen peroxide and coniferyl alcohol into the peroxidase impregnated cellulose mats through dialysis membranes. The results indicate that significant polymerization occurs within the mats. The resulting binary and ternary blends were imaged by scanning electron microscopy (SEM) and characterized by chemical means. The presence of pectin induces a better dispersion of the synthetic lignin in the cellulose network and enhances the proportion of alkyl-aryl-ether in the polymer.