Induction of the conjugative transfer of plasmids in response to pheromones

17 de May de 2017

The Institute of Health Carlos III has funded the project “Induction of the conjugative transfer of plasmids in response to pheromones” in the call Strategic Health Action 2016, File Nº: PI 16/01535 with a budget of 74,415 €.This Project is led by Mª Victoria Francia Gil, researcher at IDIVAL Group Clinical and Molecular Microbiology.

Enterococcus faecalis is a remarkable cause of opportunistic infections in hospital patients in our environment. Clinical isolates of E. faecalis are notorious for encoding resistance to multiple antibiotics. These antibiotic resistances are acquired and frequently spread by conjugation through conjugative plasmids and transposons. A feature, apparently exclusive to Enterococcus, is the role played by peptide pheromones in the transfer of conjugative plasmids. These pheromones are synthesized and secreted by all strains of E. faecalis. Pheromone response plasmids are ubiquitous in E. faecalis (including clinical isolates) and can be transferred at frequencies approaching 100%. These plasmids also improve the transfer of other elements present in the same strain. All of this suggests its importance in the spread of antibiotic resistance. Pheromone response plasmids additionally encode virulence determinants like hemolysin and aggregation substance.

The main objective of this proposal focuses on the study of the induction of the pAD1 conjugative transfer in response to the specific pheromone. pAD1 has been found in 90% of the E. faecalis clinical isolates associated with hospital outbreaks. Specifically this proposal focuses on the analysis of the activation process carried out by TraE1. The transcription start sites on TraE1-regulated operons will be identified by RNA-seq. The TraE1 mechanism of action will also be analyzed. TraE1 three-dimensional structure will be determined. TraE1 essential residues will be identified by directed mutagenesis and functional analysis. Thus, a significant progress in understanding the regulation of conjugation in response to pheromones will be achieved, allowing the development of specific inhibitors to reduce the spread of antibiotic resistance in the hospital environment.