B-280. Characterizing the Role of the Glyoxylate Pathway in Pseudomonas aeruginosa
Pseudomonas aeruginosa infections are the leading cause of lung dysfunction and mortality for Cystic Fibrosis (CF) patients. The ability of P. aeruginosa to maintain decade long infections within the CF lung is largely attributed to the utilization of chronic virulence mechanisms, some of which evolve as P. aeruginosa adapts to this environment. In a previous analysis, we determined that acute and chronic isolates of P. aeruginosa are dependent upon aceA, encoding for isocitrate lyase, to cause disease on alfalfa seedlings and for acute isolates to cause disease in rat lungs. Isocitrate lyase is one of two major enzymes of the glyoxylate pathway, which utilizes acetate or fatty acids to replenish intermediates of the TCA cycle. The glyoxylate pathway has recently been shown to play a role in chronic infections of other pathogens and the lack of glyoxylate enzymes in humans suggests these enzymes may be of therapeutic value. In this study we characterize the role of the glyoxylate pathway enzymes, isocitrate lyase (ICL) and malate synthase (MS), in the physiology of a CF adapted P. aeruginosa isolate, FRD1. The genes encoding for the ICL and MS activity were verified to be aceA and glcB respectively by mutational and enzymatic analysis. Unexpectedly, ICL and MS activities were increased in FRD1 cell free extracts compared to extracts of a non-CF isolate, PAO1, suggesting that these genes underwent adaptation in FRD1 within the CF lung. Similarly, aceA and glcB transcription were also increased in FRD1 compared to PAO1 suggesting altered regulation of these genes in the FRD1 isolate. Our current data suggest the loss of a negative regulator for aceA in FRD1 accounts for increased ICL and MS activity and that upregulation of the glyoxylate enzymes facilitates adaptation of P. aeruginosa to the CF lung.