Chromosome mobilization of Legionella pneumophila with RK2::Mu and Tn5-Mob

RK2::Mu plasmids and transposon Tn5-Mob were used to mobilize the Legionella pneumophila chromosome. Plate matings between L. pneumophila donors that contained RK2::Mu plasmids and auxotrophic recipients yielded recombinants at fequencies ranging from 10−6 to 10−7 per recipient for the markers tested. The presence of a Mu insertion in the chromosome of donors that harbored RK2::Mu plasmids increased the frequency of chromosome transfer of certain selected markers as compared with strains that contained RK2::Mu alone. Cotransfer experiments with Mu-containing donors and a thymidine and tryptophan auxotroph failed to reveal any linkage between the thy and trp loci in L. pneumophila. A strain that contained a chromosomal Tn5-Mob insertion and helper plasmid pRK24.4 transferred chromosomal markers at frequencies of 10−7 per recipient. These findings suggest that RK2::Mu plasmids and Tn5-Mob may be useful for genetic mapping experiments with L. pneumophila. Key words: Legionella pneumophila, chromosome transfer, Tn5-Mob, RK2::Mu.