Pseudomonas aeruginosa is a gram negative, opportunistic pathogen that causes chronic and acute infections in immune-compromised patients. Some P. aeruginosa strains have acquired genes that encode an active type III secretion system (T3SS). The T3SS is used by the bacteria to deliver effector proteins from the bacterial cell directly into the cytoplasm of the host cell. Four T3SS effectors have been discovered in P. aeruginosa: ExoT, ExoS, ExoU and ExoY. This is especially intriguing in light of P. aeruginosa`s ability to infect a wide range of hosts. We therefore hypothesized that other yet unknown T3SS effectors must be encoded in the genome of P. aeruginosa.
In a previous study conducted in our lab, which searched for novel T3SS effectors in Pseudomonas aeruginosa, we applied a set of machine-learning classification algorithms to distinguish effectors from non-effectors among all ORFs in this bacterium, based on various effector-characterizing features. Using this approach, two novel effectors were discovered, both of which are translocated in a T3SS dependent manner.
The main goal of my work has been to elucidate the function of the newly identified effectors. This was accomplished by utilizing three different infection models: (i) Mammalian cell lines – testing the cytotoxicity of the effectors; (ii) Saccharomyces cerevisiae – testing the toxicity of effectors in yeast cells under normal and stress conditions (e.g. salt and high temperature); and (iii) Plants – using plant models to verify translocation of effectors and to identify their possible involvement in the ability of P. aeruginosa to induce infection in plants.
