Plasmids and Symbiotic Effectiveness of Representative Phage Types from Two Indigenous Populations of Rhizobium meliloti

Abstract

Phage types representative of the population of indigenous Rhizobium mezilotiat each of two sites were evaluated for plasmid content by agarose gel electrophoresis and for symbiotic effectiveness with Medicago sativa cv. Saranac. Relative to four strains used commercially, 55 and 65 phage types representing these populations showed a high average level of symbiotic effectiveness; only a single type from one site was relatively ineffective in symbiosis. On the basis of plasmid number and molecular mass, 160 isolates comprising 45 and 48 types from both sites were placed in 22 different groups with 17 and 13 groups from the respective sites. The number of plasmids varied between one and five per isolate with molecular masses ranging from 5 MDa to considerably greater than 267 MDa. Only five isolates lacked a plasmid with mobility in agarose gels corresponding to that of a reference megaplasmid but instead showed a band of lesser mobility and therefore greater molecular mass. Phage types, which were divided into plasmid groups solely on the basis of differences between isolates from each site, may reflect adaptation of R. meIiIoti to their respective sites. Differences between isolates within certain phage types due to the presence or absence of a single plasmid May have resulted from genetic interchange between indigenous R. meliloti. There was no significant correlation between plasmid number or mass and symbiotic effectiveness or phage sensitivity of the phage types from either site.

Ensifer, Phyllobacterium and Rhizobium species occupy nodules of Medicago sativa (alfalfa) and Melilotus alba (sweet clover) grown at a Canadian site without a history of cultivation

“…Analysis of plasmid content was done by horizontal agarose gel electrophoresis as described by Bromfield et al (1987). Blotting, labelling ( 32 P) and hybridization with DNA probes for nifH and nodC genes was as described by Barran et al (1994).…”

“…Blotting, labelling ( 32 P) and hybridization with DNA probes for nifH and nodC genes was as described by Barran et al (1994). Estimates of the molecular size of bacterial plasmids were made by reference to standard plasmids of 410, 270, 180 and 55 kb in Rhizobium radiobacter PD67 (Bromfield et al, 1987). The megaplasmid band of E. meliloti SU47, consisting of pSymA (~1300 kb) and pSymB (~1700 kb) (Barnett et al, 2001), was used as a standard to detect plasmids of equivalent mobility.…”

Genetic analysis of a region of the Rhizobium meliloti pSym plasmid specifying catabolism of trigonelline, a secondary metabolite present in legumes

“…R. meliloti plasmids were detected on horizontal agarose gels by a modification of the Eckhardt technique as described by Bromfield et al (8). Total R. meliloti DNA was isolated by the method of Boucher et al (7).…”

Transcriptional regulation and locations of Agrobacterium tumefaciens genes required for complete catabolism of octopine

“…Bacterial cells were lysed and size fractionated by gel electrophoresis by the method of Eckhardt (11) as modified previously (2,27). Electrophoresis was conducted with either constant voltage and 0.5% agarose gels or by field inversion gel electrophoresis (FIGE) and 0.8% agarose gels.…”