scholarly journals A Rhizobium leguminosarum Biovar trifolii Locus Not Localized on the Sym Plasmid Hinders Effective Nodulation on Plants of the Pea Cross-Inoculation Group

1997 ◽  
Vol 10 (7) ◽  
pp. 938-941 ◽  
Author(s):  
Henk P. Roest ◽  
Ine H. M. Mulders ◽  
Herman P. Spaink ◽  
Carel A. Wijffelman ◽  
Ben J. J. Lugtenberg
Keyword(s):  
Rhizobium Leguminosarum ◽  
Outer Membrane Proteins ◽  
Extracellular Polysaccharides ◽  
Fixed Nitrogen ◽  
Significant Similarity ◽  
Sym Plasmid ◽  
Flanking Regions ◽  
Rhizobium Leguminosarum Biovar Trifolii ◽  
Inoculation Group

Introduction of the Sym plasmid pRL1JI into the cured Rhizobium leguminosarum bv. trifolii strain RCR5 resulted in a strain, designated RBL5523, that was expected to nodulate plants of the pea cross-inoculation group. However, effective nodulation occurred only on Vicia sativa plants, not on V. hirsuta or Pisum sativum. After random Tn5 mutagenesis, a derivative of RBL5523 was isolated that effectively nodulated and fixed nitrogen on P. sativum and V. hirsuta. Characterization of the mutant, RBL5787, indicated the cell surface components, extracellular polysaccharides, lipopolysaccharides, and outer membrane proteins, as well as the pattern of Nod metabolites, were indistinguishable from those of the parental strain. To obtain an indication of the function of the mutated locus, the flanking regions were sequenced and used to perform searches in protein and nonredundant nucleotide databases. No significant similarity or homology with any known sequence was detected.

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 an aromatic amino acid aminotransferase from Rhizobium leguminosarum biovar trifolii

Biochimie ◽  
1992 ◽  
Vol 74 (6) ◽  
pp. 539-544 ◽  
Author(s):  
R. Pérez-Galdona ◽  
J. Corzo ◽  
M.A. León-Barrios ◽  
A.M. Gutiérrez-Navarro
Keyword(s):  
Amino Acid ◽  
Aromatic Amino Acid ◽  
Rhizobium Leguminosarum ◽  
Rhizobium Leguminosarum Biovar Trifolii ◽  
Aromatic Amino Acid Aminotransferase

scholarly journals Distribution of O-acetyl groups in the exopolysaccharide synthesized by Rhizobium leguminosarum strains is not determined by the Sym plasmid

1991 ◽  
Vol 266 (15) ◽  
pp. 9556-9564
Author(s):  
H.C. Cremers ◽  
M. Batley ◽  
J.W. Redmond ◽  
A.H. Wijfjes ◽  
B.J. Lugtenberg ◽  
...  
Keyword(s):  
Rhizobium Leguminosarum ◽  
Sym Plasmid

Slow rehydration improves the recovery of dried bacterial populations

1992 ◽  
Vol 38 (6) ◽  
pp. 520-525 ◽  
Author(s):  
J. W. Kosanke ◽  
R. M. Osburn ◽  
G. I. Shuppe ◽  
R. S. Smith
Keyword(s):  
Relative Humidity ◽  
Rhizobium Leguminosarum ◽  
Moisture Absorption ◽  
Rhizobium Meliloti ◽  
Bacterial Populations ◽  
Bulk Powder ◽  
Alfalfa Seed ◽  
Powder Samples ◽  
Cellular Stresses ◽  
Rhizobium Leguminosarum Biovar Trifolii

Slow rehydration of bacteria from dried inoculant formulations provided higher viable counts than did rapid rehydration. Estimates were higher when clay and peat powder formulations of Rhizobium meliloti, Rhizobium leguminosarum biovar trifolii, and Pseudomonas putida, with water activities between 0.280 and 0.650, were slowly rehydrated to water activities of approximately 0.992 before continuing the dilution plating sequence. Rhizobium meliloti populations averaged 6.8 × 108 cfu/g and 1328 cfu/alfalfa seed greater when slowly rehydrated from bulk powder and preinoculated seeds, respectively. Bulk powder samples were slowly rehydrated to 0.992 water activity by the gradual addition of diluent, followed by a 10-min period for moisture equilibration. Preinoculated seed samples were placed in an environmental chamber at 24 °C with relative humidity greater than 80% for 1 h to allow moisture absorption. "Upshock," osmotic cellular stresses that occur during rehydration, was reduced when dried microbial formulations were slowly rehydrated and equilibrated before becoming fully hydrated in the dilution plating sequence. These procedures may also be applicable when estimating total viable bacterial populations from dried soil or other dry formulations. Key words: rehydration procedure, microbial rehydration, desiccation, Rhizobium, Pseudomonas.

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