Abstract
Pseudomonas aeruginosa is a pathogen that can colonize the lungs of cystic fibrosis
patients leading to chronic infections that are thought to have biofilm etiology. This opportunistic
bacterium produces three exopolysaccharides found in the biofilm matrix: PEL, PSL and
alginate. In this thesis, understanding the synthesis and expression of PEL was conducted by
developing complementation vectors for each gene in the pel operon, as well as proposed genes
involved in precursor synthesis. These vectors can be manipulated to learn more about how the
proteins function to contribute to PEL expression, as shown using the PelA complementation
vector to dissect individual residue functions. Results also suggest that the epimerases, GalE and
PA4068, contribute to the synthesis of PEL. It was also found that in vivo, PEL and PSL act as
immunosuppressive virulence factors, impairing neutrophil activation, potentially leading to
immune evasion through alteration in innate immune response.
