scholarly journals Biosynthesis of UDP-xylose and UDP-arabinose in Sinorhizobium meliloti 1021: first characterization of a bacterial UDP-xylose synthase, and UDP-xylose 4-epimerase

Microbiology ◽  
2011 ◽  
Vol 157 (1) ◽  
pp. 260-269 ◽  
Author(s):  
Xiaogang Gu ◽  
Sung G. Lee ◽  
Maor Bar-Peled
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Glucuronic Acid ◽  
Functional Studies ◽  
H Nmr ◽  
New Information ◽  
Genes Encoding ◽  
Rhizobial Species ◽  
Insight Into

Sinorhizobium meliloti is a soil bacterium that fixes nitrogen after being established inside nodules that can form on the roots of several legumes, including Medicago truncatula. A mutation in an S. meliloti gene (lpsB) required for lipopolysaccharide synthesis has been reported to result in defective nodulation and an increase in the synthesis of a xylose-containing glycan. Glycans containing xylose as well as arabinose are also formed by other rhizobial species, but little is known about their structures and the biosynthetic pathways leading to their formation. To gain insight into the biosynthesis of these glycans and their biological roles, we report the identification of an operon in S. meliloti 1021 that contains two genes encoding activities not previously described in bacteria. One gene encodes a UDP-xylose synthase (Uxs) that converts UDP-glucuronic acid to UDP-xylose, and the second encodes a UDP-xylose 4-epimerase (Uxe) that interconverts UDP-xylose and UDP-arabinose. Similar genes were also identified in other rhizobial species, including Rhizobium leguminosarum, suggesting that they have important roles in the life cycle of this agronomically important class of bacteria. Functional studies established that recombinant SmUxs1 is likely to be active as a dimer and is inhibited by NADH and UDP-arabinose. SmUxe is inhibited by UDP-galactose, even though this nucleotide sugar is not a substrate for the 4-epimerase. Unambiguous evidence for the conversions of UDP-glucuronic acid to UDP-α-d-xylose and then to UDP-β-l-arabinose (UDP-arabinopyranose) was obtained using real-time 1H-NMR spectroscopy. Our results provide new information about the ability of rhizobia to form UDP-xylose and UDP-arabinose, which are then used for the synthesis of xylose- and arabinose-containing glycans.

scholarly journals Binding Site Determinants for the LysR-Type Transcriptional Regulator PcaQ in the Legume Endosymbiont Sinorhizobium meliloti

2007 ◽  
Vol 190 (4) ◽  
pp. 1237-1246 ◽  
Author(s):  
Allyson M. MacLean ◽  
Michelle I. Anstey ◽  
Turlough M. Finan
Keyword(s):  
Binding Site ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Transcriptional Start Site ◽  
Mesorhizobium Loti ◽  
Equilibrium Dissociation ◽  
Dyad Symmetry

ABSTRACT LysR-type transcriptional regulators represent one of the largest groups of prokaryotic regulators described to date. In the gram-negative legume endosymbiont Sinorhizobium meliloti, enzymes involved in the protocatechuate branch of the β-ketoadipate pathway are encoded within the pcaDCHGB operon, which is subject to regulation by the LysR-type protein PcaQ. In this work, purified PcaQ was shown to bind strongly (equilibrium dissociation constant, 0.54 nM) to a region at positions −78 to −45 upstream of the pcaD transcriptional start site. Within this region, we defined a PcaQ binding site with dyad symmetry that is required for regulation of pcaD expression in vivo and for binding of PcaQ in vitro. We also demonstrated that PcaQ participates in negative autoregulation by monitoring expression of pcaQ via a transcriptional fusion to lacZ. Although pcaQ homologues are present in many α-proteobacteria, this work describes the first reported purification of this regulator, as well as characterization of its binding site, which is conserved in Agrobacterium tumefaciens, Rhizobium leguminosarum, Rhizobium etli, and Mesorhizobium loti.

Diversity of symbiotic rhizobia resident in Canadian soils

2003 ◽  
Vol 83 (Special Issue) ◽  
pp. 311-319 ◽  
Author(s):  
D. Prévost and E. S P. Bromfield
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Genetic Manipulation ◽  
Genotypic Variation ◽  
Natural Soil ◽  
Symbiotic Association ◽  
Canadian Soils ◽  
Plant Growth Promoting ◽  
Rhizobial Species ◽  
Biological Nitrogen

The dependency of agriculture on nitrogen fertilizer inputs is associated with adverse effects on the environment and human health. The importance of biological nitrogen fixation by rhizobia in symbiotic association with legumes is underscored by its potential to reduce or replace chemical fertilizer inputs. This paper reviews research on the diversity of the symbiotic rhizobia resident in Canadian soils. Research has focussed on phenotypic and genotypic variation (e.g., nitrogen fixing efficacy, nodulating competitiveness, host range, adaptation to cool climate) within rhizobial species with the objective of selecting efficient strains for use in inoculants for legume crops. The genetic diversity of rhizobia resident in Canadian soils has been reported only for Sinorhizobium meliloti, Rhizobium leguminosarum and Mesorhizobium spp. There is a need for further studies on populations of other rhizobial species, particularly those associated with native legumes. Exploiting the diversity present in natural soil populations via selection and genetic manipulation should permit the development of superior strains for use in legume inoculants. Other rhizobial traits that may be exploited include plant growth-promoting activity and ability to degrade pollutants. Key words: Symbiotic rhizobia, diversity, Canadian soils

scholarly journals Molecular characterization of the bet genes encoding glycine betaine synthesis in Sinorhizobium meliloti 102F34

Microbiology ◽  
1997 ◽  
Vol 143 (4) ◽  
pp. 1369-1379 ◽  
Author(s):  
J.-A. Pocard ◽  
N. Vincent ◽  
E. Boncompagni ◽  
L. T. Smith ◽  
M.-C. Poggi ◽  
...  
Keyword(s):  
Molecular Characterization ◽  
Glycine Betaine ◽  
Sinorhizobium Meliloti ◽  
Genes Encoding

scholarly journals Structural characterization of a novel subfamily of leucine-rich repeat proteins from the human pathogenLeptospira interrogans

2015 ◽  
Vol 71 (6) ◽  
pp. 1351-1359 ◽  
Author(s):  
Isabelle Miras ◽  
Frederick Saul ◽  
Mireille Nowakowski ◽  
Patrick Weber ◽  
Ahmed Haouz ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Cell Attachment ◽  
Leucine Rich Repeat ◽  
Host Proteins ◽  
Repeat Proteins ◽  
Number Of Genes ◽  
Genes Encoding ◽  
Host Cell Attachment ◽  
Insight Into

PathogenicLeptospiraspp. are the agents of leptospirosis, an emerging zoonotic disease. Analyses ofLeptospiragenomes have shown that the pathogenic leptospires (but not the saprophytes) possess a large number of genes encoding proteins containing leucine-rich repeat (LRR) domains. In other pathogenic bacteria, proteins with LRR domains have been shown to be involved in mediating host-cell attachment and invasion, but their functions remain unknown inLeptospira. To gain insight into the potential function of leptospiral LRR proteins, the crystal structures of four LRR proteins that represent a novel subfamily with consecutive stretches of a 23-amino-acid LRR repeat motif have been solved. The four proteins analyzed adopt the characteristic α/β-solenoid horseshoe fold. The exposed residues of the inner concave surfaces of the solenoid, which constitute a putative functional binding site, are not conserved. The various leptospiral LRR proteins could therefore recognize distinct structural motifs of different host proteins and thus serve separate and complementary functions in the physiology of these bacteria.

scholarly journals Characterization of Rhizobial Isolates of Phaseolus vulgaris by Staircase Electrophoresis of Low-Molecular-Weight RNA

2001 ◽  
Vol 67 (2) ◽  
pp. 1008-1010 ◽  
Author(s):  
Encarna Velázquez ◽  
Esperanza Martı́nez-Romero ◽  
Dulce Nombre Rodrı́guez-Navarro ◽  
Martha E. Trujillo ◽  
Antonio Daza ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Phaseolus Vulgaris ◽  
Rhizobium Leguminosarum ◽  
Low Molecular Weight ◽  
Rna Molecules ◽  
Rhizobial Species ◽  
The Common ◽  
Rhizobium Gallicum ◽  
Rhizobial Isolates

ABSTRACT Low-molecular-weight (LMW) RNA molecules were analyzed to characterize rhizobial isolates that nodulate the common bean growing in Spain. Since LMW RNA profiles, determined by staircase electrophoresis, varied across the rhizobial species nodulating beans, we demonstrated that bean isolates recovered from Spanish soils presumptively could be characterized as Rhizobium etli,Rhizobium gallicum, Rhizobium giardinii,Rhizobium leguminosarum bv. viciae and bv. trifolii, andSinorhizobium fredii.

TheglcBlocus ofRhizobium leguminosarumVF39 encodes an arabinose-inducible malate synthase

2002 ◽  
Vol 48 (10) ◽  
pp. 922-932 ◽  
Author(s):  
Alejandro García-de los Santos ◽  
Alejandro Morales ◽  
Laura Baldomá ◽  
Scott R.D Clark ◽  
Susana Brom ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Plant Cell Wall ◽  
Glyoxylate Cycle ◽  
Malate Synthase ◽  
Mesorhizobium Loti ◽  
Malate Synthase G ◽  
Similar Genome Organization ◽  
The Glyoxylate Cycle

In the course of a study conducted to isolate genes upregulated by plant cell wall sugars, we identified an arabinose-inducible locus from a transcriptional fusion library of Rhizobium leguminosarum VF39, carrying random insertions of the lacZ transposon Tn5B22. Sequence analysis of the locus disrupted by the transposon revealed a high similarity to uncharacterized malate synthase G genes from Sinorhizobium meliloti, Agrobacterium tumefaciens, and Mesorhizobium loti. This enzyme catalyzes the condensation of glyoxylate and acetyl-CoA to yield malate and CoA and is thought to be a component of the glyoxylate cycle, which allows microorganisms to grow on two carbon compounds. Enzyme assays showed that a functional malate synthase is encoded in the glcB gene of R. leguminosarum and that its expression is induced by arabinose, glycolate, and glyoxylate. An Escherichia coli aceB glcB mutant, complemented with the R. leguminosarum PCR-amplified gene, recovered malate synthase activity. A very similar genome organization of the loci containing malate synthase and flanking genes was observed in R. leguminosarum, S. meliloti, and A. tumefaciens. Pea plants inoculated with the glcB mutant or the wild-type strain showed no significant differences in nitrogen fixation. This is the first report regarding the characterization of a mutant in one of the glyoxylate cycle enzymes in the rhizobia.Key words: Rhizobium, malate synthase, glyoxylate cycle, arabinose metabolism.

scholarly journals Copolymer chain formation of 2-oxazolines by in situ1H-NMR spectroscopy: dependence of sequential composition on substituent structure and monomer ratios

RSC Advances ◽  
2021 ◽  
Vol 11 (18) ◽  
pp. 10468-10478
Author(s):  
Sabina Abbrent ◽  
Andrii Mahun ◽  
Miroslava Dušková Smrčková ◽  
Libor Kobera ◽  
Rafał Konefał ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Polymer Chains ◽  
Chain Formation ◽  
Molar Ratios ◽  
H Nmr ◽  
Copolymer Chain ◽  
Nmr Characterization ◽  
Insight Into

In situ1H NMR characterization of copolymerization reactions of various 2-oxazoline monomers at different molar ratios offers detailed insight into the build-up and composition of the polymer chains.

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