- THIS ARTICLE
- Full Text (PDF)
- Alert me when this article is cited
- Alert me if a correction is posted
- SERVICES
- Similar articles in this journal
- Similar articles in PubMed
- Alert me to new issues of the journal
- Download to citation manager
- Reprints & Permissions
- CITING ARTICLES
- Citing Articles via HighWire
- Citing Articles via Google Scholar
- GOOGLE SCHOLAR
- Articles by Oresnik, I. J.
- Articles by Finan, T. M.
- Search for Related Content
- PUBMED
- PubMed Citation
- Articles by Oresnik, I. J.
- Articles by Finan, T. M.
Genetics, Vol 136, 1233-1243, Copyright © 1994
INVESTIGATIONS |
Second Site Mutations Specifically Suppress the Fix(-) Phenotype of Rhizobium meliloti ndvF Mutations on Alfalfa: Identification of a Conditional ndvF-Dependent Mucoid Colony Phenotype
I. J. Oresnik, T. C. Charles and T. M. Finan
Department of Biology, McMaster University, West, Hamilton, Ontario L8S 4K1, Canada
Rhizobium meliloti mutants carrying ndvF insertion or deletion mutations induce nodules on alfalfa which contain very few infected cells and fail to fix N(2) (Fix(-)). We have characterized five independent second site mutations (designated sfx) which completely suppress the Fix(-) phenotype of ndvF mutants on Medicago sativa but not on another R. meliloti host Melilotus alba. Genetic mapping and phenotypic analysis revealed that the suppressor mutations sfx-1, sfx-4 and sfx-5 mapped to a single locus which was distinct from another locus defined by the sfx-2 and sfx-3 mutations. Tn5-mob-mediated conjugal mapping experiments showed that the sfx-1 locus was located clockwise from trp-33 on the R. meliloti chromosome and a detailed cotransduction map of this region was generated. To clone the sfx-1 locus, we prepared a cosmid library from total DNA obtained from an sfx-1, ndvF deletion strain. From this library, a cosmid pTH56, which converted Fix(-) ndvF mutants to Fix(+), was isolated. Southern blot analysis provided direct physical evidence that the insert DNA in plasmid pTH56 was contiguous with the sfx-1 region. On low osmolarity glutamate-yeast extract-mannitol-salts medium (GYM) agar medium, ndvF insertion and deletion mutants were found to have a mucoid colony phenotype, as opposed to the dry colony phenotype of the wild-type strain. This phenotype was shown to be dependent on the exoB and expE genes required for synthesis of exopolysaccharide II in R. meliloti but not to be dependent on genes required exclusively for the synthesis of the succinoglycan or exopolysaccharide I. Transduction of either sfx-1 or sfx-2 or transfer of the cosmid pTH56 into the ndvF mutants restored them to a wild-type dry colony phenotype. The mucoid phenotype is not responsible for the Fix(-) phenotype of ndvF mutants as the Fix(-), ndvF exp double mutants can be complemented to Fix(+) by introducing plasmids which carry only the wild-type ndvF genes.
This article has been cited by other articles:
 |
|
 |
|
  N. J. Poysti and I. J. Oresnik Characterization of Sinorhizobium meliloti Triose Phosphate Isomerase Genes J. Bacteriol., May 1, 2007; 189(9): 3445 - 3451. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. J. Poysti, E. D. M. Loewen, Z. Wang, and I. J. Oresnik Sinorhizobium meliloti pSymB carries genes necessary for arabinose transport and catabolism Microbiology, March 1, 2007; 153(3): 727 - 736. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Miller-Williams, P. C. Loewen, and I. J. Oresnik Isolation of salt-sensitive mutants of Sinorhizobium meliloti strain Rm1021 Microbiology, July 1, 2006; 152(7): 2049 - 2059. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z.-C. Yuan, R. Zaheer, and T. M. Finan Regulation and Properties of PstSCAB, a High-Affinity, High-Velocity Phosphate Transport System of Sinorhizobium meliloti J. Bacteriol., February 1, 2006; 188(3): 1089 - 1102. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. S. Richardson, M. F. Hynes, and I. J. Oresnik A Genetic Locus Necessary for Rhamnose Uptake and Catabolism in Rhizobium leguminosarum bv. trifolii J. Bacteriol., December 15, 2004; 186(24): 8433 - 8442. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. E. Mendrygal and J. E. González Environmental Regulation of Exopolysaccharide Production in Sinorhizobium meliloti J. Bacteriol., February 1, 2000; 182(3): 599 - 606. [Abstract] [Full Text]
|
|
|
|
 |
|
 I. J. Oresnik, S. Twelker, and M. F. Hynes Cloning and Characterization of a Rhizobium leguminosarum Gene Encoding a Bacteriocin with Similarities to RTX Toxins Appl. Envir. Microbiol., July 1, 1999; 65(7): 2833 - 2840. [Abstract] [Full Text]
|
|
|
|
|
|
M. L. Summers, M. C. Denton, and T. R. McDermott Genes Coding for Phosphotransacetylase and Acetate Kinase in Sinorhizobium meliloti Are in an Operon That Is Inducible by Phosphate Stress and Controlled by PhoB J. Bacteriol., April 1, 1999; 181(7): 2217 - 2224. [Abstract] [Full Text]
|
|
|
|
|
|
S. D. Bardin, R. T. Voegele, and T. M. Finan Phosphate Assimilation in Rhizobium (Sinorhizobium) meliloti: Identification of a pit-Like Gene J. Bacteriol., August 15, 1998; 180(16): 4219 - 4226. [Abstract] [Full Text]
|
|
|
|
 |
|
 S. D. Bardin and T. M. Finan Regulation of Phosphate Assimilation in Rhizobium (Sinorhizobium) meliloti Genetics, April 1, 1998; 148(4): 1689 - 1700. [Abstract] [Full Text] [PDF]
|
|