Large indigenous plasmids are a common feature in members of the genus Rhizobium, and their involvement in the control of symbiotic functions has been established. Studies on these rhizobial plasmids, called pSym plasmids, make up much of what is understood about the molecular and genetic basis of the N2-fixing symbiosis. The soybeans, generally nodulated by slow-growing rhizobia, are an econom...

Southern hybridization with nif (nitrogen fixation) and nod (nodulation) DNA probes from Rhizobium meliloti against intact plasmid DNA of Rhizobium japonicum and Bradyrhizobium japonicum strains indicated that both nif and nod sequences are on plasmid DNA in most R. japonicum strains. An exception is found with R. japonicum strain USDA194 and all B. japonicum strains where nif and nod sequences...

other Rhizobium species. Most of these plasmids encoding for fixation and nodulation properties are non-self transmissible. Plasmid profiles were determined for 24 strains of R. trifolii. All the strains harboured at least three plasmids and as many as eight were present in some strains. Southern hybridization with cloned R. meliloti nifgenes was used to identify indigenous Nif plasmids. Each s...

Rhodococcus equi is an important bacterial pathogen in foals up to 6 months old, widespread in horse farms all over the world. It was found that only virulent R. equi strains expressing 15-17 kDa virulence-associated protein (VapA) and having large virulence plasmid of 85-90 kb containing vapA gene are pathogenic for horses. To date, 12 plasmid types have been reported in VapA positive strains ...

We present a method for cloning restriction-modification (R-M) systems that is based on the use of a lethal plasmid (pKILLER). The plasmid carries a functional gene for a restriction endonuclease having the same DNA specificity as the R-M system of interest. The first step is the standard preparation of a representative, plasmid-borne genomic library. Then this library is transformed with the k...