Conjugative transfer and in vitro/in vivo stability of the broad-host-range IncP R751 plasmid in Brucella spp.

Escherichia coli strain K12 BM14, carrying plasmid R751 (51.4 kb; Tpr, Tra+, IncP), was used as donor in matings with reference strains of the six Brucella nomenspecies, not known so far to harbor naturally occurring plasmids. R751 was easily transferred to and between Brucella spp., at frequencies ranging between 10(-1) and 10(-4). All Brucella transconjugants stably maintained plasmid R751 both in vitro and in vivo in our experimental conditions. No genetic modification of the plasmid during and after the conjugal transfer process could be deduced from the comparative restriction analysis (BamHI, HindIII, and EcoRI) in each Brucella transconjugant and in the E. coli donor.