Experimental Evolution to Identify Mutations that Compensate for Loss of Xenogeneic Silencing Proteins in Salmonella Typhimurium

Horizontal Gene Transfer (HGT) is an important process that has driven the evolution of bacteria, and has been particularly important in the development of pathogenic strains. Foreign genes, however, pose a considerable risk to bacteria. The foreign gene silencing proteins H-NS and StpA buffer the fitness costs associated with HGT. To gain insight into how these proteins act as global regulators and to observe the functional consequences of losing these proteins, I employed an in vitro evolution approach with Salmonella strains harbouring deletions in both hns and stpA. I show that passaging over 500 generations partially restores fitness and using whole genome sequencing, identify recurring mutations within chaperones DnaK/DnaJ and the transcription termination factor Rho. My results provide important insights into how H-NS/ StpA likely coordinate with Rho to silence foreign genes and regulate HGT.M.Sc.2018-11-21 00:00:0