Stability and transmissibility of the cryptic plasmids of Rhizobium meliloti GR4

1993 ◽  
Vol 160 (6) ◽  
pp. 477-485 ◽  
Author(s):  
Jes�s Mercado-Blanco ◽  
Jos� Olivares
Keyword(s):  
Rhizobium Meliloti ◽  
Cryptic Plasmids

A cryptic plasmid of indigenous Rhizobium meliloti possesses reiterated nodC and nifE genes and undergoes DNA rearrangement

1992 ◽  
Vol 38 (6) ◽  
pp. 563-568 ◽  
Author(s):  
V. K. Rastogi ◽  
E. S. P. Bromfield ◽  
S. T. Whitwill ◽  
L. R. Barran
Keyword(s):  
Genomic Dna ◽  
Rhizobium Meliloti ◽  
Phage Type ◽  
Cryptic Plasmid ◽  
Dna Rearrangement ◽  
Homologous Sequences ◽  
Phage Types ◽  
Phage Sensitivity ◽  
Cryptic Plasmids ◽  
Free Strain

Indigenous Rhizobium meliloti were previously characterized on the basis of plasmid profiles and phage sensitivity patterns (phage types). Rhizobium meliloti 1076, which contained two cryptic plasmids, was one of four isolates comprising phage type 23. In this study, the large cryptic plasmid pVS1(size >500 b) was transferred from isolate 1076 into the plasmid-free strain of Agrobacterium tumefaciens UBAPF1. This plasmid contained nucleotide sequences homologous to genes for nodulation (nodB, nodC) and nitrogen fixation (nifH, nifD, nifK, nifE). Cosmid clones possessing the nod and nif homologous sequences, which had been selected from a genomic bank of A. tumefaciens UBAPF1 containing pVS1, complemented R. meliloti nodC and nifE mutants, respectively. These results demonstrate that the nodC and nifE homologous sequences are functionally expressed. Three of four isolates comprising phage type 23 possessed a megaplasmid band in agarose gels characteristic of R. meliloti, as well as two cryptic plasmids. The fourth isolate (No. 323) lacked the large cryptic plasmid corresponding to pVS1, but instead showed a band of lesser mobility than that of the megaplasmids. Nevertheless, its restricted genomic DNA retained the nodC and nifE hybridizing fragments characteristic of pVS1, indicating that the cryptic plasmid has undergone DNA rearrangement. Key words: Rhizobium, plasmid, reiteration, genes, rearrangement.

scholarly journals Cloning and Identification of Conjugative Transfer Origins in the Rhizobium meliloti Genome

1998 ◽  
Vol 180 (17) ◽  
pp. 4583-4590 ◽  
Author(s):  
Jose A. Herrera-Cervera ◽  
Julio M. Sanjuan-Pinilla ◽  
Jose Olivares ◽  
Juan Sanjuan
Keyword(s):  
Dna Hybridization ◽  
Rhizobium Meliloti ◽  
Restriction Analysis ◽  
Recipient Cell ◽  
Conjugative Plasmid ◽  
Conjugative Transfer ◽  
Mobilizable Plasmid ◽  
The Family ◽  
Cryptic Plasmids ◽  
Plasmid Replicons

ABSTRACT A simple approach was used to identify Rhizobium meliloti DNA regions with the ability to convert a nontransmissible vector into a mobilizable plasmid, i.e., to contain origins of conjugative transfer (oriT,mob). RecA-defective R. meliloti merodiploid populations, where each individual contained a hybrid cosmid from anR. meliloti GR4 gene library, were used as donors en masse in conjugation with another R. meliloti recipient strain, selecting transconjugants for vector-encoded antibiotic resistance. Restriction analysis of cosmids isolated from individual transconjugants resulted in the identification of 11 nonoverlapping DNA regions containing potential oriTs. Individual hybrid cosmids were confirmed to be mobilized from the originalrecA donors at frequencies ranging from 10−2to 10−5 per recipient cell. DNA hybridization experiments showed that seven mob DNA regions correspond to plasmid replicons: four on symbiotic megaplasmid 1 (pSym1), one on pSym2, and another two on each of the two cryptic plasmids harbored by R. meliloti GR4. Another three mob clones could not be located to any plasmid and were therefore preliminarily assigned to the chromosome. With this strategy, we were able to characterize theoriT of the conjugative plasmid pRmeGR4a, which confirmed the reliability of the approach to select for oriTs. Moreover, transfer of the 11 mob cosmids from R. meliloti into Escherichia coli occurred at frequencies as high as 10−1, demonstrating the R. meliloti gene transfer capacity is not limited to the familyRhizobiaceae. Our results show that the R. meliloti genome contains multiple oriTs that allow efficient DNA mobilization to rhizobia as well as to phylogenetically distant gram-negative bacteria.

Promiscuous nodulation of Phaseolus vulgaris, Macroptilium atropurpureum, and Leucaena leucocephala by indigenous Rhizobium meliloti

1990 ◽  
Vol 36 (5) ◽  
pp. 369-372 ◽  
Author(s):  
E. S. P. Bromfield ◽  
L. R. Barran
Keyword(s):  
Phaseolus Vulgaris ◽  
Host Range ◽  
Leucaena Leucocephala ◽  
Rhizobium Meliloti ◽  
Symbiotic Genes ◽  
Apparent Relationship ◽  
Macroptilium Atropurpureum ◽  
Axenic Conditions ◽  
Cryptic Plasmids ◽  
Reference Strains

Thirty-three isolates of indigenous Rhizobium meliloti, either possessing cryptic plasmids that hybridize to probes for symbiotic genes or lacking a 1500-kb megaplasmid band in Eckhardt gels, were tested for infectivity on 10 legume species grown under axenic conditions. A previous study had shown that all but two isolates were symbiotically effective with Medicago sativa. All indigenous isolates and two reference strains of R. meliloti induced nodules which were symbiotically ineffective on Trigonella foenum-graecum (100% plants nodulated) and Phaseolus vulgaris (40 to 100% plants nodulated). Eighteen indigenous isolates of R. meliloti elicited ineffective nodules on Macroptilium atropurpureum (2 to 25% plants nodulated) and Leucaena leucocephala (11 to 75% plants nodulated). The identity of single colony nodule isolates from each R. meliloti inoculant and host combination was verified by phage typing and analysis of plasmid profiles; tests with subsamples of these isolates showed that all were capable of nodulating M. sativa. There was no apparent relationship between the host range of indigenous R. meliloti and either the presence of cryptic plasmids that hybridize to probes for symbiotic genes or the absence of a megaplasmid band in Eckhardt gels. The data suggest that nodulation promiscuity may be a relatively common characteristic of R. meliloti. Key words: host range, Rhizobium meliloti, Leucaena, Macroptilium, Phaseolus.

Symbiotic gene probes hybridize to cryptic plasmids of indigenous Rhizobium meliloti

1988 ◽  
Vol 34 (5) ◽  
pp. 703-707 ◽  
Author(s):  
L. R. Barran ◽  
E. S. P. Bromfield
Keyword(s):  
Dna Sequences ◽  
Rhizobium Meliloti ◽  
Dna Probes ◽  
Cryptic Plasmid ◽  
Nodule Development ◽  
Nif Genes ◽  
Symbiotic Gene ◽  
Gene Probes ◽  
Cryptic Plasmids

DNA probes for host specific nodulation (hsn) common nodulation (nod), exopolysaccharide (exo), nodule development (ndv) and nitrogenase structural (nif) genes were used to examine a collection of symbiotically effective, genotypically distinct isolates of indigenous Rhizobium meliloti for reiteration of symbiotic DNA sequences on cryptic plasmids. Nineteen of 30 isolates possessed at least one cryptic plasmid with reiterated DNA sequences, and of these isolates 15, 5, and 1 contained cryptic plasmids that hybridized to hsn, nif, and nod gene probes respectively; both hsn and nif probes hybridized to a single cryptic plasmid in each of two isolates. The exo and ndv probes did not hybridize to cryptic plasmids in any of the 30 isolates of R. meliloti.

EFFECTS OF SOIL ACIDITY ON RHIZOBIA NUMBERS, NODULATION AND NITROGEN FIXATION BY ALFALFA AND RED CLOVER

1977 ◽  
Vol 57 (2) ◽  
pp. 197-203 ◽  
Author(s):  
W. A. RICE ◽  
D. C. PENNEY ◽  
M. NYBORG
Keyword(s):  
Nitrogen Fixation ◽  
Soil Ph ◽  
Soil Acidity ◽  
Field Experiments ◽  
Rhizobium Meliloti ◽  
Acid Soils ◽  
Red Clover ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Greenhouse Experiments

The effects of soil acidity on nitrogen fixation by alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were investigated in field experiments at 28 locations, and in greenhouse experiments using soils from these locations. The pH of the soils (limed and unlimed) varied from 4.5 to 7.2. Rhizobia populations in the soil, nodulation, and relative forage yields (yield without N/yield with N) were measured in both the field and greenhouse experiments. Rhizobium meliloti numbers, nodulation scores, and relative yields of alfalfa decreased sharply as the pH of the soils decreased below 6.0. For soils with pH 6.0 or greater, there was very little effect of pH on any of the above factors for alfalfa. Soil pH in the range studied had no effect on nodulation scores and relative yields of red clover. However, R. trifolii numbers were reduced when the pH of the soil was less than 4.9. These results demonstrate that hydrogen ion concentration is an important factor limiting alfalfa growth on acid soils of Alberta and northeastern British Columbia, but it is less important for red clover. This supports the continued use of measurements of soil pH, as well as plant-available Al and Mn for predicting crop response to lime.

scholarly journals Electrophoretic separation of the three Rhizobium meliloti replicons.

1991 ◽  
Vol 173 (16) ◽  
pp. 5173-5180 ◽  
Author(s):  
B W Sobral ◽  
R J Honeycutt ◽  
A G Atherly ◽  
M McClelland
Keyword(s):  
Rhizobium Meliloti ◽  
Electrophoretic Separation
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