Integrating conjugative elements of the SXT/R391 family trigger the excision and drive the mobilization of a new class of Vibrio genomic islands.
In vibrios and enterobacteria lateral gene transfer is often facilitated by integrating conjugative elements (ICEs) of the SXT/R391 family. SXT/R391 ICEs integrate by site-specific recombination into prfC and transfer by conjugation, a process that is initiated at a specific locus called the origin of transfer (oriT(SXT) ). We identified genomic islands (GIs) harbouring a sequence that shares >63% identity with oriT(SXT) in three species of Vibrio. Unlike SXT/R391 ICEs, these GIs are integrated into a gene coding for a putative stress-induced protein and do not appear to carry any gene coding for a conjugative machinery or for mobilization proteins. Our results show that SXT/R391 ICEs trigger the excision and mediate the conjugative transfer in trans of the three Vibrio GIs at high frequency. GIs' excision is independent of the ICE-encoded recombinase and is controlled by the ICE-encoded transcriptional activator SetCD, which is expressed during the host SOS response. Both mobI and traI, two ICE-borne genes involved in oriT recognition, are essential for GIs' transfer. We also found that SXT/R391 ICEs mobilize in trans over 1 Mb of chromosomal DNA located 5' of the GIs' integration site. Together these results support a novel mechanism of mobilization of GIs by ICEs of the SXT/R391 family.
Daccord
Aurélie
A
Centre d'Étude et de Valorisation de la Diversité Microbienne (CEVDM), Département de biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
Ceccarelli
Daniela
D
Burrus
Vincent
V
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements; D044404:Genomic Islands; D008969:Molecular Sequence Data; D005810:Multigene Family; D045522:Recombinases / Q000235:genetics; D011995:Recombination, Genetic; D014733:Vibrio / Q000201:enzymology / Q000235:genetics*
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D045522:Recombinases