Isolated plasmid DNA from Rhizobium leguminosarum was hybridised with cellular RNA from broth-cultured bacteria and endosymbiotic bacteroids. From these hybridisation, experiments it is concluded that plasmid genes are strongly expressed in bacteroids and only weakly or not at all in bacteria. From the hybridisation of plasmid DNA with the cloned structural nif genes of Klebsiella pneumoniae it...

We developed a rapid, inexpensive method for isolating and identifying Rhizobium leguminosarum by. phaseoli strains from bean root nodules. The method can be used for other small or medium-sized nodules such as those of clover, alfalfa and peas. With this method, one person can process 115 nodules/h. Using a simple apparatus made of plexiglass and machine bolts, we simultaneously crushed 24 sur...

We compared the nodulation competitiveness of three strains of Rhizobium leguminosarum by counting the number of nodules formed on faba bean plants after the application at sowing time of different concentrations of the strains to soils already containing Rhizobium strains of the same species. A relationship of type y = ax was found to exist between the ratio of the nodules formed by the applie...

Physiological responses to infection by strains of Rhizobium leguminosarum which differed in their capacity to reduce N(2) were determined in 26-day-old pea plants (Pisum sativum L. cv. Alaska) grown under uniform environmental conditions in the absence of combined N. The highest N(2) reduction rates, calculated from H(2) evolution and C(2)H(2)-dependent C(2)H(4) production measurements, were a...

Of 18 Rhizobium trifolii strains tested, 12 showed a high frequency of loss of nodulation ability after incubation in cultures at elevated temperatures. A correlation between loss of nodulation ability and loss of a large plasmid was demonstrated for R. trifolii. In some nonnodulating (Nod-) mutants, deletions occurred instead of total elimination of the plasmid molecule. The maximum curing eff...

The effect of host plant cultivar on H(2) evolution by root nodules was examined in symbioses between Pisum sativum L. and selected strains of Rhizobium leguminosarum. Hydrogen evolution from root nodules containing Rhizobium represents the sum of H(2) produced by the nitrogenase enzyme complex and H(2) oxidized by any uptake hydrogenase present in those bacterial cells. Relative efficiency (RE...

Carboxymethyl cellulase and polygalacturonase activities were evaluated in wild-type strains from different taxonomic groups of rhizobia which nodulate a specific range of legume hosts that do not normally overlap (R. meliloti, R. loti, R. leguminosarum biovar trifolii, R. leguminosarum biovar phaseoli, R. leguminosarum biovar viceae, and Bradyrhizobium japonicum). To detect these enzymatic act...

In wild-type Rhizobium leguminosarum, the sitABCD operon specifies a Mn(2+) transporter whose expression is severely reduced in cells grown in the presence of this metal. Mutations in the R. leguminosarum gene, mur (manganese uptake regulator), whose product resembles the Fur transcriptional regulator, cause high-level expression of sitABCD in the presence of Mn(2+). In gel-shift mobility assay...