The 90 kilobase pair virulence plasmid of salmonella serovar typhimurium coexists in strains with a plasmid of the 23 incompatibility groups

Strains containing the 90 kilobase pair (kb) virulence plasmid of Salmonella ser Typhimurium or a cointegrate of which a part was the 90 kb plasmid were mated with strains harboring the plasmid of the 23 known incompatibility groups. Transconjugants, selected for the incoming plasmids, were isolated and purified, and their plasmid content was examined by agarose gel electrophoresis. The 90 kb plasmid can coexist for at least 54 generations with all the 23 plasmids of the known incompatibility groups tested.