Cryptic plasmids with different molecular weights have been detected in B. pseudomallei strains. Mobilization of B. pseudomallei plasmid DNA in heterologous B. mallei species was performed by the conjugate plasmid RP1::Tn10. Possibility of detecting phenotypical characteristics of plasmids and behavior of B. pseudomallei non-chromosomal replicons in B. mallei have been determined.