Characterization of structural defects in the lipopolysaccharides of symbiotically impaired Rhizobium leguminosarum biovar viciae VF-39 mutants

1992 ◽  
Vol 231 ◽  
pp. 261-271 ◽  
Author(s):  
Yuanda Zhang ◽  
Rawle I. Hollingsworth ◽  
Ursula B. Priefer
Keyword(s):  
Rhizobium Leguminosarum ◽  
Structural Defects

Towards 3D image-based nanocrystallography by means of transmission electron goniometry

2004 ◽  
Vol 839 ◽  
Author(s):  
Peter Moeck ◽  
Wentao Qin ◽  
Philip B. Fraundorf
Keyword(s):  
Lattice Structure ◽  
Three Dimensions ◽  
Structural Defects ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Z Contrast ◽  
Individual Nanoparticles ◽  
Nanocrystal Model ◽  
The Ideal

ABSTRACTIt is well known that the crystallographic phase and morphology of many materials changes with the crystal size in the tens of nanometer range and that many nanocrystals possess structural defects in excess of their equilibrium levels. A need to determine the ideal and real structure of individual nanoparticles, therefore, arises. High-resolution phase-contrast transmission electron microscopy (TEM) and atomic resolution Z-contrast scanning TEM (STEM) when combined with transmission electron goniometry offer the opportunity of develop dedicated methods for the crystallographic characterization of nanoparticles in three dimensions. This paper describes tilt strategies for taking data from individual nanocrystals “as found”, so as to provide information on their lattice structure and orientation, as well as on the structure and orientation of their surfaces and structural defects. Internet based java applets that facilitate the application of this technique for cubic crystals with calibrated tilt-rotation and double-tilt holders are mentioned briefly. The enhanced viability of image-based nanocrystallography in future aberration-corrected TEMs and STEMs is illustrated on a nanocrystal model system.

Synchrotron white beam x-ray topography characterization of structural defects in microgravity and ground-based CdZnTe crystals

1996 ◽  
Author(s):  
Hua Chung ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
David J. Larson, Jr.
Keyword(s):  
Structural Defects ◽  
X Ray ◽  
White Beam

Genetic characterization of Rhizobium sp. strain TAL1145 that nodulates tree legumes

1994 ◽  
Vol 40 (3) ◽  
pp. 208-215 ◽  
Author(s):  
M. L. C. George ◽  
J. P. W. Young ◽  
D. Borthakur
Keyword(s):  
Rhizobium Leguminosarum ◽  
Genetic Characterization ◽  
Rhizobium Meliloti ◽  
Wild Type ◽  
Tree Legumes ◽  
Wide Range ◽  
The Common ◽  
Rrna Sequences ◽  
Rhizobium Sp

Rhizobium sp. strain TALI 145 nodulates Leucaena ieucocephaia and Phaseolus vulgaris, in addition to a wide range of tropical tree legumes. Six overlapping clones that complemented nodulation defects in leucaena and bean rhizobia were isolated and a 40-kb map of the symbiosis region was constructed. The common nod and nifA genes were situated approximately 17 kb apart, with the nodlJ genes in between. These clones enabled a derivative of TAL1145 carrying a partially deleted pSym to form ineffective nodules on both leucaena and bean, and a similar derivative of Rhizobium etli TAL182 to form ineffective nodules on bean. When two representative clones, pUHR9 and pUHR114, were each transferred to wild-type rhizobial strains, they allowed ineffective nodulation by Rhizobium meliloti on both leucaena and bean and by Rhizobium leguminosarum bv. viciae on bean. Transconjugants of R. leguminosarum bv. trifolii formed effective nodules on leucaena and ineffective nodules on bean. Tn5 mutagenesis of the symbiosis region resulted in a variety of nodulation and fixation phenotypes on leucaena and bean. On the basis of 16S rRNA sequences, TAL1145 was found to be distinct from both R. tropici and NGR234, the two groups of leucaena symbionts that were previously described.Key words: Rhizobium, Leucaena leucocephala, nodulation, nitrogen fixation.

Study on Dispersion and Characterization of Functionalized MWCNTs Prepared by Wet Oxidation

2014 ◽  
Vol 661 ◽  
pp. 8-13 ◽  
Author(s):  
Intan Syaffinazzilla Zaine ◽  
N.A.M. Napiah ◽  
Azmi Mohamad Yusof ◽  
A.N. Alias ◽  
A.M.M. Ali ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Relative Intensity ◽  
Colloidal Stability ◽  
Structural Defects ◽  
Wet Oxidation ◽  
Defect Level ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Functionalized Mwcnts

The MWCNTs was functionalized by refluxing commercial MWCNTs (a-MWCNTs) in concentrated HNO3/H2SO4 (3:1 v/v) at 100°C for 6 hours. The dispersion of a-MWCNTs and functionalized MWCNTs (f-MWCNTs) were observed after 1 hour sonication in ethanol. Both samples were characterized by UV-vis spectroscopy for dispersion behavior. The dried f-MWCNTs and a-MWCNTs were characterized by Raman spectroscopy to estimate the defect level. The morphology of the samples were analyzed by Transmission Electron Microscopy (TEM). The f-MWCNTs was well dispersed in ethanol within 2 weeks of observations period. The colloidal stability of a-MWCNTs was low as it was easily sediment after 24 hours. The UV-vis spectra of f-MWCNTs show maximum absorbance at 250 nm meanwhile no absorbance was observed for a-MWCNTs. Analysis from Raman spectrum shows that the f-MWCNTs have relative intensity of 1.101 which is higher than a-MWCNTs that have relative intensity of 0.935. The image from TEM revealed that the f-MWCNTs have structural defects and the absence of amorphous carbon on sidewall meanwhile the a-MWCNTs indicate otherwise.

Characterization of structural defects in the presence of In2O3 in CuInSe2 prepared by spray pyrolysis

Solar Cells ◽  
1990 ◽  
Vol 28 (3) ◽  
pp. 177-183 ◽  
Author(s):  
Belgacem Haba ◽  
Clayton W. Bates ◽  
Brian J. Brown ◽  
Zolili Ndlela ◽  
Greg Smestad
Keyword(s):  
Spray Pyrolysis ◽  
Structural Defects

scholarly journals Identification and Characterization of a Bacteroid-Specific Dehydrogenase Complex in Rhizobium leguminosarum PRE

1988 ◽  
Vol 54 (12) ◽  
pp. 3008-3013 ◽  
Author(s):  
René M. Klein Lankhorst ◽  
Panagiotis Katinakis ◽  
Albert van Kammen ◽  
Rommert C. van den Bos
Keyword(s):  
Rhizobium Leguminosarum ◽  
Identification And Characterization ◽  
Dehydrogenase Complex

scholarly journals Chemical characterization of effective and ineffective strains of Rhizobium leguminosarum bv. viciae.

1999 ◽  
Vol 46 (4) ◽  
pp. 1001-1009
Author(s):  
S F Izmailov ◽  
G Y Zhiznevskaya ◽  
L V Kosenko ◽  
G N Troitskaya ◽  
N N Kudryavtseva ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Rhizobium Leguminosarum ◽  
Unsaturated Fatty Acids ◽  
Effective Strain ◽  
Chemical Characterization ◽  
Unsaturation Index ◽  
Fa Composition ◽  
Sds Page ◽  
Lower Molecular Mass

Chemical composition of lipopolysaccharide (LPS) isolated from an effective (97) and ineffective (87) strains of R. l. viciae has been determined. LPS preparations from the two strains contained: glucose, galactose, mannose, fucose, arabinose, heptose, glucosamine, galactosamine, quinovosamine, and 3-N-methyl-3,6-dideoxyhexose, as well as glucuronic, galacturonic and 3-deoxyoctulosonic acid. The following fatty acids were identified: 3-OH 14:0, 3-OH 15:0, 3-OH 16:0, 3-OH 18:0 and 27-OH 28:0. The ratio of 3-OH 14:0 to other major fatty acids in LPS 87 was higher that in LPS 97. SDS/PAGE profiles of LPS indicated that, in lipopolysaccharides, relative content of S form LPS I to that of lower molecular mass (LPS II) was much higher in the effective strain 97 than in 87. All types of polysaccharides exo-, capsular-, lipo, (EPS, CPS, LPS, respectively) examined possessed the ability to bind faba bean lectin. The degree of affinity of the host lectin to LPS 87 was half that to LPS 97. Fatty acids (FA) composition from bacteroids and peribacteroid membrane (PBM) was determined. Palmitic, stearic and hexadecenoic acids were common components found in both strains. There was a high content of unsaturated fatty acids in bacteroids as well as in PBM lipids. The unsaturation index in the PBM formed by strain 87 was lower than in the case of strain 97. Higher ratio of 16:0 to 18:1 fatty acids was characteristic for PMB of the ineffective strain.

scholarly journals Regulation and characterization of mutants of fixABCX in Rhizobium leguminosarum.

2021 ◽  
Author(s):  
Isabel Webb ◽  
Jiabao Xu ◽  
Carmen Sanchez-Cañizares ◽  
Ramakrishnan Karunakaran ◽  
Vinoy Ramachandran ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Rhizobium Leguminosarum ◽  
Redox Balance ◽  
Rna Seq ◽  
Wild Type ◽  
Transcription Start Sites ◽  
Sym Plasmid ◽  
Microaerobic Conditions ◽  
Type Infection

Symbiosis between Rhizobium leguminosarum and Pisum sativum requires tight control of redox balance in order to maintain respiration under the microaerobic conditions required for nitrogenase, whilst still producing the eight electrons and sixteen molecules of ATP needed for nitrogen fixation. FixABCX, electron transfer flavoproteins essential for nitrogen fixation, are encoded on the Sym plasmid (pRL10), immediately upstream of nifA, which encodes the general transcriptional regulator of nitrogen fixation. There is a symbiotically-regulated NifA-dependent promoter upstream of fixA (PnifA1), as well as an additional basal constitutive promoter driving background expression of nifA (PnifA2). These were confirmed by 5’-end mapping of transcription start sites using differential (d) RNA-seq. Complementation of polar fixAB and fixX mutants (Fix- strains) confirmed expression of nifA from PnifA1 in symbiosis. Electron microscopy combined with single-cell Raman microspectroscopy characterization of fixAB mutants revealed previously unknown heterogeneity in bacteroid morphology within a single nodule. Two morphotypes of mutant fixAB bacteroids were observed. One was larger than wild-type bacteroids and contained high levels of polyhydroxy-3-butyrate, a complex energy/reductant storage product. A second bacteroid phenotype was morphologically and compositionally different and resembled wild-type infection thread cells. From these two characteristic fixAB mutant bacteroid morphotypes, inferences can be drawn on the metabolism of wild-type nitrogen-fixing bacteroids.

Characterization of Symbiotic Genes and Regulation of Their Expression in Rhizobium Leguminosarum PRE

1987 ◽  
pp. 241-243 ◽  
Author(s):  
Jan Hontelez ◽  
Rene Klein Lankhorst ◽  
Jan-Dirk Jansma ◽  
Evert Jacobsen ◽  
Rommert C. van den Bos ◽  
...  
Keyword(s):  
Rhizobium Leguminosarum ◽  
Symbiotic Genes
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