title: Conjugative transfer and cis-mobilization of a genomic island by an integrative and conjugative element of Streptococcus agalactiae.
abstract: Putative integrative and conjugative elements (ICEs), i.e., genomic islands which could excise, self-transfer by conjugation, and integrate into the chromosome of the bacterial host strain, were previously identified by in silico analysis in the sequenced genomes of Streptococcus agalactiae (M. Brochet et al., J. Bacteriol. 190:6913-6917, 2008). We investigated here the mobility of the elements integrated into the 3' end of a tRNA(Lys) gene. Three of the four putative ICEs tested were found to excise but only one (ICE_515_tRNA(Lys)) was found to transfer by conjugation not only to S. agalactiae strains but also to a Streptococcus pyogenes strain. Transfer was observed even if recipient cell already carries a related resident ICE or a genomic island flanked by attL and attR recombination sites but devoid of conjugation or recombination genes (CIs-Mobilizable Element [CIME]). The incoming ICE preferentially integrates into the 3' end of the tRNA(Lys) gene (i.e., the attR site of the resident element), leading to a CIME-ICE structure. Transfer of the whole composite element CIME-ICE was obtained, showing that the CIME is mobilizable in cis by the ICE. Therefore, genomic islands carrying putative virulence genes but lacking the mobility gene can be mobilized by a related ICE after site-specific accretion.
authors.affiliation: INRA, UMR1128 Génétique et Microbiologie, Faculté des Sciences et Technologies, Vandœuvre-lès-Nancy, France.
authors.forename: Aurore
authors.initials: A
authors.lastname: Puymège
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bertin
authors.forename: Sarah
authors.initials: S
authors.lastname: Chuzeville
authors.forename: Gérard
authors.initials: G
authors.lastname: Guédon
authors.forename: Sophie
authors.initials: S
authors.lastname: Payot
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D001483:Base Sequence; D003227:Conjugation, Genetic; D022761:Gene Transfer, Horizontal; D044404:Genomic Islands; D016366:Open Reading Frames; D012357:RNA, Transfer, Lys / Q000235:genetics*; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D013292:Streptococcus agalactiae / Q000235:genetics*; D013297:Streptococcus pyogenes / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; D012357:RNA, Transfer, Lys