Structurally diverse chitolipooligosaccharide Nod factors accumulate primarily in membranes of wild-type Rhizobium leguminosarum biovar trifolii

Biochemistry ◽  
1995 ◽  
Vol 34 (11) ◽  
pp. 3832-3840 ◽  
Author(s):  
Guy G. Orgambide ◽  
Jeongrim Li ◽  
Rawle I. Hollingsworth ◽  
Frank B. Dazzo
Keyword(s):  
Rhizobium Leguminosarum ◽  
Nod Factors ◽  
Wild Type ◽  
Rhizobium Leguminosarum Biovar Trifolii

scholarly journals The Production of Species-Specific Highly Unsaturated Fatty Acyl-Containing LCOs from Rhizobium leguminosarum bv. trifolii Is Stringently Regulated by nodD and Involves the nodRL Genes

2006 ◽  
Vol 19 (3) ◽  
pp. 215-226 ◽  
Author(s):  
Helmi R. M. Schlaman ◽  
Maurien M. A. Olsthoorn ◽  
Marga Harteveld ◽  
Lucie Dörner ◽  
Michael A. Djordjevic ◽  
...  
Keyword(s):  
Rhizobium Leguminosarum ◽  
Growth Conditions ◽  
Fatty Acyl ◽  
Nod Factors ◽  
Wild Type ◽  
Reading Frame ◽  
Nod Genes ◽  
Geographical Regions ◽  
Acyl Chains ◽  
Species Specific

A proportion of the Nod factors of some Rhizobium leguminosarum bv. trifolii strains is characterized by the presence of highly unsaturated fatty acyl chains containing trans double bonds in conjugation with the carbonyl group of the glycan oligosaccharide backbone. These fatty acyl chains are C18:3, C20:3, C18:4, or C20:4 and have UV-absorption maxima at 303 and 330 nm. These Nod factors are presumed to be important for host-specific nodulation on clover species. However, in wild-type R. leguminosarum bv. trifolii ANU843, Nod factors with these characteristic acyl chains were not observed using standard growth conditions. They were observed only when nod genes were present in multiple copies or when transcription was artificially increased to higher levels by introduction of extra copies of the transcriptional regulator gene nodD. In a screen for the genetic requirements for production of the Nod factors with these characteristic structures, it was found that the region downstream of nodF and nodE is essential for the presence of highly unsaturated fatty acyl moieties. Mu-lacZ insertion in this region produced a mutant that did not produce detectable levels of the highly unsaturated fatty acyl-bearing Nod factors. The Mu-lacZ insertion was translationally fused to a putative new gene, designated nodR, in the nodE-nodL intergenic region; however, no predicted function for the putative NodR protein has been obtained from data-base homology searches. In a set of 12 wild-type strains of R. leguminosarum bv. trifolii originating from various geographical regions that were analyzed for the presence of a nodR-like gene, it was found that seven strains carry a homologous NodR open reading frame. Taken together, our results suggest a tightly controlled regulation of nod genes, in which we propose that it is the balance of transcriptional levels of nodFE and the nodRL genes that is critical for determining the presence of highly unsaturated fatty acyl moieties in the Nod factors produced by R. leguminosarum bv. trifolii.

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.

scholarly journals Extracellular Glycanases of Rhizobium leguminosarum Are Activated on the Cell Surface by an Exopolysaccharide-Related Component

2000 ◽  
Vol 182 (5) ◽  
pp. 1304-1312 ◽  
Author(s):  
Angeles Zorreguieta ◽  
Christine Finnie ◽  
J. Allan Downie
Keyword(s):  
Cell Wall ◽  
Agrobacterium Tumefaciens ◽  
Cell Surface ◽  
Rhizobium Leguminosarum ◽  
Plant Cell Wall ◽  
Agar Medium ◽  
Wild Type ◽  
Close Proximity ◽  
Mutant Strains ◽  
Colony Surface

ABSTRACT Rhizobium leguminosarum secretes two extracellular glycanases, PlyA and PlyB, that can degrade exopolysaccharide (EPS) and carboxymethyl cellulose (CMC), which is used as a model substrate of plant cell wall cellulose polymers. When grown on agar medium, CMC degradation occurred only directly below colonies of R. leguminosarum, suggesting that the enzymes remain attached to the bacteria. Unexpectedly, when a PlyA-PlyB-secreting colony was grown in close proximity to mutants unable to produce or secrete PlyA and PlyB, CMC degradation occurred below that part of the mutant colonies closest to the wild type. There was no CMC degradation in the region between the colonies. By growing PlyB-secreting colonies on a lawn of CMC-nondegrading mutants, we could observe a halo of CMC degradation around the colony. Using various mutant strains, we demonstrate that PlyB diffuses beyond the edge of the colony but does not degrade CMC unless it is in contact with the appropriate colony surface. PlyA appears to remain attached to the cells since no such diffusion of PlyA activity was observed. EPS defective mutants could secrete both PlyA and PlyB, but these enzymes were inactive unless they came into contact with an EPS+ strain, indicating that EPS is required for activation of PlyA and PlyB. However, we were unable to activate CMC degradation with a crude EPS fraction, indicating that activation of CMC degradation may require an intermediate in EPS biosynthesis. Transfer of PlyB to Agrobacterium tumefaciens enabled it to degrade CMC, but this was only observed if it was grown on a lawn ofR. leguminosarum. This indicates that the surface ofA. tumefaciens is inappropriate to activate CMC degradation by PlyB. Analysis of CMC degradation by other rhizobia suggests that activation of secreted glycanases by surface components may occur in other species.

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.

scholarly journals Glutathione Status in the Roots of Tomato Plants Transgenic by Genes psl and rapA1 in the Presence of Rhizobium leguminosarum

2021 ◽  
Vol 68 (5) ◽  
pp. 923-930
Author(s):  
Z. R. Vershinina ◽  
O. V. Chubukova ◽  
D. R. Maslennikova
Keyword(s):  
Solanum Lycopersicum ◽  
Bacterial Adhesion ◽  
Rhizobium Leguminosarum ◽  
De Novo ◽  
Growth Parameters ◽  
Wild Type ◽  
Leguminous Plants ◽  
Tomato Plants ◽  
Glutathione Status

Abstract The level of glutathione was investigated in the roots of tomato (Solanum lycopersicum L.) plants transgenic by genes psl and rapA1 in the presence of a microsymbiont of leguminous plants Rhizobium leguminosarum VSy3. The plants transformed with gene psl showed a greater bacterial adhesion than the plants transformed with gene rapA1, which positively correlated with growth parameters of plants. Treatment with rhizobia elevated the content of glutathione in the roots of wild type plants three times, 4.7 times in the roots of plants transformed with gene rapA1, and more than five times in the plants transgenic by gene psl. The obtained results suggest that the level of glutathione in the roots may serve as a marker of efficiency of artificial symbiotic systems produced de novo.

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.

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