Properties of an R factor from Bordetella bronchiseptica.

R906, a plasmid derived from a wild strain of Bordetella bronchiseptica, was transferred to Escherichia coli K I ~ . In this host it is stably heritable, replicating as a DNA molecule with a molecular weight of 34-6 megadaltons. There are approximately three copies of the plasmid per chromosome. It is a member of compatibility group P. In E. coli, R906 confers resistance to ampicillin, streptomycin, sulphonamides and mercury salts. Resistance to ampicillin is determined by an oxacillin-hydrolysing P-lactamase whereas the resistance to streptomycin is not determined by either of the previously described streptomycin-inactivating enzymes but by some other mechanism.