title: Self-transmissibility of the integrative and conjugative element ICEPm1 between clinical isolates requires a functional integrase, relaxase, and type IV secretion system.
abstract: Integrative and conjugative elements (ICEs), which are chromosomal mobile elements, can conjugatively transfer between bacteria. Recently, we identified a genomic island of Proteus mirabilis, a common agent of catheter-associated urinary tract infection (UTI), that possesses all the properties consistent with an ICE. This element, designated ICEPm1, is highly conserved in other causative agents of UTI, suggesting its mobility. We demonstrate that ICEPm1 can actively excise from the chromosome in a clonal population of bacteria and that this excision is integrase dependent. Although in P. mirabilis HI4320, ICEPm1 is annotated as integrated into the phenylalanine tRNA gene pheV, we show that ICEPm1 can integrate into either pheV or pheU. We determined that ICEPm1 transfers at a frequency of 1.35 × 10(-5) transconjugants/donor to ICEPm1-deficient P. mirabilis using plate mating assays with clinical isolates. Insertional inactivation of a putative integrase gene on ICEPm1 decreased transfer frequencies of ICEPm1 to below the limit of detection. Mutation of the relaxase of ICEPm1 also eliminates transfer and demonstrates that this element is indeed self-transmissible and not transferred in trans, as are some mobilizable genomic islands. Together, these findings clearly demonstrate that ICEPm1 can actively excise from the chromosome in an integrase-dependent manner, dynamically integrate into both phenylalanine tRNA genes, and transfer into clinical strains using its own conjugation machinery.
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, 5641 Medical Science Building II, 1150 West Medical Center Drive, Ann Arbor, MI 48109, USA.
authors.forename: Erika L
authors.initials: EL
authors.lastname: Flannery
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Antczak
authors.forename: Harry L T
authors.initials: HL
authors.lastname: Mobley
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D017124:Conserved Sequence; D004254:DNA Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D044404:Genomic Islands; D019426:Integrases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011513:Proteus mirabilis / Q000235:genetics / Q000378:metabolism*; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity
chemical_list: D001426:Bacterial Proteins; D012343:RNA, Transfer; D004254:DNA Nucleotidyltransferases; C110340:DNA relaxase; D019426:Integrases