title: Identification and characterization of a new conjugation/type IVA secretion system (trb/tra) of Legionella pneumophila Corby localized on two mobile genomic islands.
abstract: Horizontal gene transfer probably contributes to evolution of Legionella pneumophila and its adaptation to different environments. Although horizontal gene transfer was observed in Legionella, the mechanism is still not specified. In this study we identified and analysed a new type of conjugation/type IVA secretion system (trb/tra) of L. pneumophila Corby, a virulent human isolate. Two similar versions of this conjugation system were identified, localized on two different genomic islands (Trb-1, 42,710 bp and Trb-2, 34,434 bp). Trb-1 and Trb-2 are integrated within the tRNA(Pro) gene (lpc2778) and the tmRNA gene (lpc0164), respectively. Both islands exhibit an oriT region and both can be excised from the chromosome forming episomal circles. Trb-1 was analysed in more detail. It is active and can be horizontally transferred to other Legionella strains by conjugation and then integrated into the genome in a site-specific manner within the tRNA(Pro) gene. We characterized the sequence of the excision and integration sites of Trb-1 in three different L. pneumophila strains. Here we demonstrate that L. pneumophila exhibits a functional oriT region and that genomic islands in Legionella can be mobilized and conjugated to other species of Legionella. Thus, we describe for the first time a mechanism that may explain the observed horizontal transfer of chromosomal DNA in Legionella.
authors: Leibniz Institute for Age Research - Fritz Lipmann Institute, D-07745 Jena, Germany.
authors: Gernot
authors: G
authors: Glöckner
authors: Christiane
authors: C
authors: Albert-Weissenberger
authors: Erik
authors: E
authors: Weinmann
authors: Sebastian
authors: S
authors: Jacobi
authors: Eva
authors: E
authors: Schunder
authors: Michael
authors: M
authors: Steinert
authors: Jörg
authors: J
authors: Hacker
authors: Klaus
authors: K
authors: Heuner
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D003227:Conjugation, Genetic / Q000235:genetics* / Q000502:physiology; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D023061:Gene Order; D005798:Genes, Bacterial; D044404:Genomic Islands; D006801:Humans; D020071:Interspersed Repetitive Sequences; D016952:Legionella pneumophila / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D007877:Legionnaires' Disease / Q000382:microbiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D012329:RNA, Bacterial / Q000235:genetics; D012361:RNA, Transfer, Pro / Q000235:genetics; D011995:Recombination, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012361:RNA, Transfer, Pro; C096222:tmRNA