Entry Exclusion of Conjugative Plasmids of the IncA, IncC, and Related Untyped Incompatibility Groups.

Conjugative plasmids of incompatibility group C (IncC), formerly known as A/C, disseminate antibiotic resistance genes globally in diverse pathogenic species of genomic island 1 (SGI1) can be mobilized by IncC plasmids and was recently shown to reshape the conjugative type IV secretion system (T4SS) encoded by these plasmids to evade entry exclusion. Entry exclusion blocks DNA translocation between cells containing identical or highly similar plasmids. Here, we report that the protein encoded by the entry exclusion gene of IncC plasmids () mediates entry exclusion in recipient cells through recognition of the IncC-encoded TraG protein in donor cells.

Salmonella genomic island 1 (SGI1) reshapes the mating apparatus of IncC conjugative plasmids to promote self-propagation.

IncC conjugative plasmids and Salmonella genomic island 1 (SGI1) and relatives are frequently associated with multidrug resistance of clinical isolates of pathogenic Enterobacteriaceae. SGI1 is specifically mobilized in trans by IncA and IncC plasmids (commonly referred to as A/C plasmids) following its excision from the chromosome, an event triggered by the transcriptional activator complex AcaCD encoded by these helper plasmids. Although SGI1 is not self-transmissible, it carries three genes, traNS, traHS and traGS, coding for distant homologs of the predicted mating pore subunits TraNC, TraHC and TraGC, respectively, encoded by A/C plasmids.