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.

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 Rhizobium fix genes mediate at least two communication steps in symbiotic nodule development.

1988 ◽  
Vol 106 (3) ◽  
pp. 597-607 ◽  
Author(s):  
P Putnoky ◽  
E Grosskopf ◽  
D T Ha ◽  
G B Kiss ◽  
A Kondorosi
Keyword(s):  
Rhizobium Meliloti ◽  
Host Cells ◽  
Nodule Development ◽  
Peribacteroid Membrane ◽  
Symbiotic Gene ◽  
Morphological Studies ◽  
Group I ◽  
Infection Threads ◽  
Symbiotic Nodule ◽  
Bacterial Genes

To identify bacterial genes involved in symbiotic nodule development, ineffective nodules of alfalfa (Medicago sativa) induced by 64 different Fix-mutants of Rhizobium meliloti were characterized by assaying for symbiotic gene expression and by morphological studies. The expression of leghemoglobin and nodulin-25 genes from alfalfa and of the nifHD genes from R. meliloti were monitored by hybridizing the appropriate DNA probes to RNA samples prepared from nodules. The mutants were accordingly divided into three groups. In group I none of the genes were expressed, in group II only the plant genes were expressed and in group III all three genes were transcribed. Light and electron microscopical analysis of nodules revealed that nodule development was halted at different stages in nodules induced by different group I mutants. In most cases nodules were empty lacking infection threads and bacteroids or nodules contained infection threads and a few released bacteroids. In nodules induced by a third mutant class bacteria were released into the host cells, however the formation of the peribacteroid membrane was not normal. On this basis we suggest that peribacteroid membrane formation precedes leghemoglobin and nodulin-25 induction, moreover, after induction of nodulation by the nod genes at least two communication steps between the bacteria and the host plants are necessary for the development of the mature nodule. By complementing each mutant of group I with a genomic R. meliloti library made in pLAFRl, four new fix loci were identified, indicating that several bacterial genes are involved in late nodule development.

Identification of two fix loci controlling the expression of nif genes in Rhizobium meliloti 41

1989 ◽  
Vol 215 (2) ◽  
pp. 345-348 ◽  
Author(s):  
Z. Banfalvi ◽  
V. Petkova ◽  
M. Lados ◽  
K. Slaska-Kiss ◽  
P. Putnoky ◽  
...  
Keyword(s):  
Rhizobium Meliloti ◽  
Nif Genes

Genetic Transformation of Streptococcus sanguis (Challis) with Cryptic Plasmids from Streptococcus ferus

1980 ◽  
Vol 28 (3) ◽  
pp. 692-699 ◽  
Author(s):  
Francis L. Macrina ◽  
Patricia H. Wood ◽  
Kevin R. Jones
Keyword(s):  
Genetic Transformation ◽  
Streptococcus Mutans ◽  
Restriction Enzyme ◽  
Deoxyribonucleic Acid ◽  
Cryptic Plasmid ◽  
Common Ancestry ◽  
Erythromycin Resistance ◽  
Streptococcus Sanguis ◽  
Cryptic Plasmids ◽  
Isogenic Strains

By using the basic methodology initially published by Kretschmer et al. (J. Bacteriol. 124 :225-231, 1975), we have been able to introduce phenotypically cryptic plasmids from Streptococcus ferus (formerly Streptococcus mutans subsp. ferus ) into Streptococcus sanguis by genetic transformation. In this system, the entry of the cryptic plasmids is selected indirectly. This is effected with transforming deoxyribonucleic acid mixtures in which the cryptic plasmid deoxyribonucleic acid is present in an approximate 10-fold molar excess with respect to a plasmid (pVA1) known to confer erythromycin resistance. Under such conditions, 5 to 10% of the pVA1-containing erythromycin-resistant transformants were cotransformed with cryptic plasmid deoxyribonucleic acid. pVA1 may be selectively eliminated by growth of its S. sanguis host strain at 42°C, enabling the construction of isogenic strains with and without S. ferus cryptic plasmids. Comparative physiological studies of such strains have failed to reveal any plasmid-conferred phenotypes in S. sanguis. With this procedure, we have been able to physically separate two small cryptic plasmids (2.4 × 10 6 and 2.8 × 10 6 daltons) of S. ferus. Although these plasmids were found naturally to exist in a single S. ferus host, they were able to replicate independently of one another in S. sanguis. Restriction enzyme fingerprinting indicated that these plasmids did not share a common ancestry.

scholarly journals Clustering of nitrogen fixation (nif) genes in Rhizobium meliloti.

1982 ◽  
Vol 149 (1) ◽  
pp. 221-228 ◽  
Author(s):  
D Corbin ◽  
G Ditta ◽  
D R Helinski
Keyword(s):  
Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
Nif Genes

Characterization of incompatibility group HI1 plasmids from Salmonella typhi by restriction endonuclease digestion and hybridization of DNA probes for Tn3, Tn9, and Tn10

1985 ◽  
Vol 31 (8) ◽  
pp. 721-729 ◽  
Author(s):  
Diane E. Taylor ◽  
Elisa C. Brose
Keyword(s):  
Dna Sequences ◽  
Tetracycline Resistance ◽  
Restriction Enzymes ◽  
Salmonella Typhi ◽  
Dna Probes ◽  
Restriction Enzyme Digestion ◽  
Incompatibility Group ◽  
Chloramphenicol Resistance ◽  
F Factor ◽  
The One

Chloramphenicol resistance in Salmonella typhi is mediated by plasmids of the incompatibility group H, subgroup 1 (IncHI1). Eight IncHI1 plasmids from S. typhi strains originating in Mexico, Vietnam, Thailand, and India were examined by restriction enzyme digestion. The restriction enzymes, ApaI, XbaI, and PstI were found to be most useful for comparison of plasmid DNAs. Four plasmids from S. typhi isolated in Mexico, Vietnam, and Thailand between 1972 and 1974 had identical restriction patterns with all three enzymes. The other IncHI1 plasmids showed only minor differences. However, some significant differences were noted between these IncHI1 plasmids and the prototype IncHI1 plasmid R27, which was isolated from S. typhimurium in 1961 and for which a restriction map has been constructed. Southern transfer hybridization with a nick-translated HI1 plasmid as a probe confirmed that there is a great deal of sequence homology among the IncHI1 plasmids. DNA probes were used to locate DNA sequences for ampicillin resistance (Tn3), chloramphenicol resistance (Tn9), tetracycline resistance (Tn10), and the one-way incompatibility between IncHI1 plasmids and the F factor, a characteristic property of IncHI1 plasmids. The results demonstrate that IncHI1 plasmids isolated from S. typhi from widely different geographic sources are very similar. Comparisons between the S. typhi plasmids and R27 indicated that conserved regions of DNA were those involved in conjugative transfer.

Rhizobium meliloti exopolysaccharides: genetic analyses and symbiotic importance

1991 ◽  
Vol 19 (3) ◽  
pp. 636-644 ◽  
Author(s):  
T. Lynne Reuber ◽  
Jason Reed ◽  
Jane Glazebrook ◽  
M. Alexandra Glucksmann ◽  
Dianne Ahmann ◽  
...  
Keyword(s):  
Rhizobium Meliloti ◽  
Nodule Development ◽  
Nitrogen Fixing ◽  
Free Living ◽  
Genetic Analyses ◽  
Living State ◽  
Meliloti Strain

Summary Genetic experiments have indicated that succinoglycan (EPS I), the acidic Calcofluor-binding exopolysaccharide, of the nitrogen-fixing bacterium Rhizobium meliloti strain Rm1021 is required for nodule invasion and possibly for later events in nodule development on alfalfa and other hosts. Fourteen exo loci on the second megaplasmid have been identified that are required for, or affect, the synthesis of EPS I. Mutations in certain of these loci completely abolish the production of EPS I and result in mutants that form empty Fix- nodules. We have identified two loci, exoR and exoS, that are involved in the regulation of EPS I synthesis in the free-living state. Certain exo mutations which completely abolish EPS I production are lethal in an exoR95 or exoS96 background. Histochemical analyses of the expression of exo genes during nodulation using exo :: TnphoA fusions have indicated that the exo genes are expressed most strongly in the invasion zone. In addition, we have discovered that R. meliloti has a latent capacity to synthesize a second exopolysaccharide (EPS II) that can substitute for the role(s) of EPS I in nodulation of alfalfa but not of other hosts. Possible roles for exopolysaccharides in symbiosis are discussed.

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
Sign in / Sign up

Export Citation Format

Share Document