The Experts below are selected from a list of 2202 Experts worldwide ranked by ideXlab platform
Thierry Heulin - One of the best experts on this subject based on the ideXlab platform.
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Bacillus Polymyxa and rahnella aquatilis the dominant n2 fixing bacteria associated with wheat rhizosphere in french soils
European Journal of Soil Biology, 1994Co-Authors: Thierry Heulin, Odile Berge, L Gouzou, K.p. Hebbar, Patrick Mavingui, Jacques BalandreauAbstract:Au cours d'une etude sur les bacteries fixatrices d'azote adaptees a la rhizosphere des plantes, nous avons isole 56 souches bacteriennes representatives de la rhizosphere d'un ble de printemps (cv. Castan) ayant atteint le stade trois feuilles. L'etape d'isolement a ete realisee par enrichissement en presence d'exsudats produits par de jeunes plantules de ble germant sterilement (technique du «modele spermosphere»). Bacillus Polymyxa et Bacillus circulans sont les especes fixatrices d'azote les plus frequentes dans trois des quatre sols etudies. Dans le quatrieme sol, l'espece fixatrice d'azote dominante est Rahnella aquatilis, qui est une enterobacterie taxonomiquement proche de Enterobacter agglomerans et Erwinia herbicola (.)
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effect of inoculation with Bacillus Polymyxa on soil aggregation in the wheat rhizosphere preliminary examination
Geoderma, 1993Co-Authors: L Gouzou, G Burtin, R Philippy, Federico Bartoli, Thierry HeulinAbstract:Gouzou, L., Burtin, G., Philippy, R., Bartoli, F. and Heulin, T., 1993. Effect of inoculation with Bacillus Polymyxa on soil aggregation in the wheat rhizosphere: preliminary examination. In: L. Brussaard and M.J. Kooistra (Editors), Int. Workshop on Methods of Research on Soil Structure I Soil Biota Interrelationships. Geoderma, 56: 479–491. The present paper reports the results of a combined physical and microbial approach to studying the aggregation state of a silt loam soil in the wheat rhizosphere. Non-rhizosphere soil aggregate size distribution was attributed to self-fragmentation of clods. In contrast, aggregate size distribution was uni-modal and centered at 0.2-2 mm for soil adhering to wheat roots. On the other hand, inoculation of wheat with a rhizosphere strain of Bacillus Polymyxa increased the mass of soil adhering to the roots by 57%. Comparison of aggregate size distributions suggested a more porous structure for the inoculated rhizosphere soil than the uninoculated. An avidin-biotin indirect ELISA procedure, which allows the detection of B. Polymyxa in its natural environment, indicated that the population remained at a constant level whatever the treatment or the size of aggregates. Aggregate stability in water, which was low, showed no statistical difference between treatments or between aggregate size fractions. The water-stable aggregates studied here represent the elementary rhizosphere aggregates characterized by the association of clays, silts, fine sands and B. Polymyxa cells. No effect on the population level of B. Polymyxa or on the stabilization of aggregates was observed after inoculation of soil and seeds. However, a more porous structure developed within the rhizosphere soil. We are continuing to investigate this aspect of the soil structure process which could be related to a spatial extension of the rhizosphere soil. Inoculation by B. Polymyxa could play an important role in water retention and nutrient transfer in the rhizosphere through increasing porosity.
Tamaichi Ashida - One of the best experts on this subject based on the ideXlab platform.
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Crystallization and preliminary x-ray analysis of beta-amylase from Bacillus Polymyxa.
Acta Crystallographica Section D Biological Crystallography, 1999Co-Authors: Takashi Yamane, Hiroshi Tasaki, Fusako Matsumoto, Atsuo Suzuki, Nobuyuki Uozumi, Tamaichi AshidaAbstract:A truncated β-amylase (E.C. 3.2.1.2) from Bacillus Polymyxa has been crystallized using the hanging-drop vapour-diffusion method at 277 K. The crystals belong to the orthorhombic space group P212121 with cell dimensions a = 64.6, b = 141.9, c = 155.1 A and diffract to 2.5 A resolution. The asymmetric unit containing three protein molecules was derived from an electron-density map calculated at 4 A resolution using MIR phases. This gives a Vm value of 2.36 A3 Da−1.
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Crystallization and preliminary x-ray analysis of beta-amylase from Bacillus Polymyxa.
Acta crystallographica. Section D Biological crystallography, 1999Co-Authors: Takashi Yamane, Hiroshi Tasaki, Fusako Matsumoto, Atsuo Suzuki, Nobuyuki Uozumi, Tamaichi AshidaAbstract:A truncated beta-amylase (E.C. 3.2.1.2) from Bacillus Polymyxa has been crystallized using the hanging-drop vapour-diffusion method at 277 K. The crystals belong to the orthorhombic space group P212121 with cell dimensions a = 64.6, b = 141.9, c = 155.1 A and diffract to 2.5 A resolution. The asymmetric unit containing three protein molecules was derived from an electron-density map calculated at 4 A resolution using MIR phases. This gives a Vm value of 2.36 A3 Da-1.
Pierre Strehaiano - One of the best experts on this subject based on the ideXlab platform.
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Production of xylanases by Bacillus Polymyxa using lignocellulosic wastes
Industrial Crops and Products, 1998Co-Authors: Phuong Lan Pham, Patricia Taillandier, Michel Delmas, Pierre StrehaianoAbstract:Production of xylanolytic enzymes with no detectable cellulase activity was investigated using two strains of Bacillus Polymyxa. The optimum pH and temperature for activities of the two xylanases ranged from 6.0 to 7.0 and from 45 to 50°C, respectively. The highest titres of xylanase, up to 24 nKat ml^-1 were produced within 36 and 42 h, respectively in shake flask cultures at 30°C. Enzyme production showed a cell growth associated profile. One of two strains, B. Polymyxa CECT 153 was chosen for further detailed study. Numerous carbohydrates were examined for their ability to induce xylanase. It was found that xylan or xylan containing substrates, such as wheat straw, induced maximum and comparable levels of xylanase, while pure cellulose (avicel, a-cellulose) and the easily metabolisable sugars (glucose, sucrose) did not improve xylanase synthesis. Low levels of constitutive enzyme were produced as evidence from the culture medium without carbon source addition. Among various nitrogen sources tested, yeast extract was optimal for the production of xylanase.
Nobuyuki Uozumi - One of the best experts on this subject based on the ideXlab platform.
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Crystallization and preliminary x-ray analysis of beta-amylase from Bacillus Polymyxa.
Acta Crystallographica Section D Biological Crystallography, 1999Co-Authors: Takashi Yamane, Hiroshi Tasaki, Fusako Matsumoto, Atsuo Suzuki, Nobuyuki Uozumi, Tamaichi AshidaAbstract:A truncated β-amylase (E.C. 3.2.1.2) from Bacillus Polymyxa has been crystallized using the hanging-drop vapour-diffusion method at 277 K. The crystals belong to the orthorhombic space group P212121 with cell dimensions a = 64.6, b = 141.9, c = 155.1 A and diffract to 2.5 A resolution. The asymmetric unit containing three protein molecules was derived from an electron-density map calculated at 4 A resolution using MIR phases. This gives a Vm value of 2.36 A3 Da−1.
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Crystallization and preliminary x-ray analysis of beta-amylase from Bacillus Polymyxa.
Acta crystallographica. Section D Biological crystallography, 1999Co-Authors: Takashi Yamane, Hiroshi Tasaki, Fusako Matsumoto, Atsuo Suzuki, Nobuyuki Uozumi, Tamaichi AshidaAbstract:A truncated beta-amylase (E.C. 3.2.1.2) from Bacillus Polymyxa has been crystallized using the hanging-drop vapour-diffusion method at 277 K. The crystals belong to the orthorhombic space group P212121 with cell dimensions a = 64.6, b = 141.9, c = 155.1 A and diffract to 2.5 A resolution. The asymmetric unit containing three protein molecules was derived from an electron-density map calculated at 4 A resolution using MIR phases. This gives a Vm value of 2.36 A3 Da-1.
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structural and functional roles of cysteine residues of Bacillus Polymyxa beta amylase
Biochemistry, 1991Co-Authors: Nobuyuki Uozumi, Tsukasa Matsuda, Norihiro Tsukagoshi, Shigezo UdakaAbstract:Bacillus Polymyxa beta-amylase contains three cysteine residues at positions 83, 91, and 323, which can react with sulfhydryl reagents. To determine the role of cysteine residues in the catalytic reaction, cysteine residues were mutated to construct four mutant enzymes, C83S, C91V, C323S, and C-free. Wild-type and mutant forms of the enzyme were expressed in, and purified to homogeneity from, Bacillus subtilis. A disulfide bond between Cys83 and Cys91 was identified by isolation of tryptic peptides bearing a fluorescent label, IAEDANS, from wild-type and C91 V enzymes followed by amino acid sequencing. Therefore, only Cys323 contains a free SH group. Replacement of cysteine residues with serine or valine residues resulted in a significant decrease in the kcat/Km value of the enzyme. C323S, containing no free SH group, however, retained a high specific activity, approximately 20% of the wild-type enzyme. None of the cysteine residues participate directly in the catalytic reaction.
J A Pérez-gonzález - One of the best experts on this subject based on the ideXlab platform.
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Purification and characterization of an arabinofuranosidase from Bacillus Polymyxa expressed in Bacillus subtilis.
Applied microbiology and biotechnology, 1995Co-Authors: P Morales, J M Sendra, J A Pérez-gonzálezAbstract:Two polypeptides showing alpha-L-arabinofuranosidase activity have been purified to homogeneity from culture supernatants of a Bacillus subtilis clone harbouring the xynD gene [Gosalbes et al. (1991) J Bacteriol 173: 7705-7710] from Bacillus Polymyxa. Both polypeptides, with determined molecular masses of 64 kDa and 53 kDa, share the same sequence at their N termini, which also coincides with the sequence deduced for the mature protein from the previously determined sequence of nucleotides (Gosalbes et al. 1991). The two polypeptides have been biochemically characterized. Arabinose is the unique product released from arabinose-containing xylans which are substrates for both enzyme forms. Other natural arabinose-containing polysaccharides, such as arabinogalactans, are not attacked by them but some artificial arabinose derivatives are good substrates for both polypeptides. Their arabinose-releasing activity on arabinoxylans facilitates the hydrolysis of the xylan backbone by some endoxylanases from Bacillus Polymyxa.
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Purification and characterization of a xylanase and an arabinofuranosidase from Bacillus Polymyxa
Enzyme and Microbial Technology, 1995Co-Authors: P Morales, J M Sendra, Alejo Madarro, Agustí Flors, J A Pérez-gonzálezAbstract:Abstract Two hemicellulases from Bacillus Polymyxa were purified and characterized: a xylanase with a molecular mass of 61 kD and pl of 4.7 and an arabinofuranosidase with a molecular mass of 166 kD and pl of 4.7. The xylanase, which showed increased thermostability in the presence of MgCl 2 , showed a typical endo-action mode on xylans from several sources. The arabinofuranosidase was only active on (1→5)-α- l -arabinooligosaccharides but not on linear (1→5)-α- l -arabinan, arabinogalactan, and arabinoxylan. However, it was able to release arabinose from arabinoxylan when an active endoxylanase was also present in hydrolysis assays.
