Replication and Active Partition of Integrative and Conjugative Elements (ICEs) of the SXT/R391 Family: The Line between ICEs and Conjugative Plasmids Is Getting Thinner

摘要: Integrative and Conjugative Elements (ICEs) of the SXT/R391 family disseminate multidrug resistance among pathogenic Gammaproteobacteria such as Vibrio cholerae. ICEs are mobile genetic elements that reside in chromosome their host eventually self-transfer to other bacteria by conjugation. transfer involves a transient extrachromosomal circular plasmid-like form is thought be substrate for single-stranded DNA translocation recipient cell through mating pore. This non-replicative consequently expected highly unstable. We report here ICE R391 Providencia rettgeri impervious loss upon division. have investigated determinants contributing stability. First, we found hipAB-like toxin/antitoxin system improves stability its deletion resulted tenfold increase loss. Because hipAB not conserved feature ICEs, sought alternative stabilization mechanisms. conjugation itself does stabilize traG, which abolishes conjugative transfer, did influence frequency However, either relaxase-encoding gene traI or origin (oriT) led dramatic correlated with copy number decrease form. observation suggests replication initiated at oriT TraI essential only but also ICEs. Finally, uncovered srpMRC, locus coding two proteins distantly related type II (actin-type ATPase) parMRC partitioning plasmid R1. assays demonstrate srpMRC active contributes reducing While systems usually stabilizes low-copy plasmids, first reported