Genome-scale modeling of Pseudomonas aeruginosa PA14 unveils its broad metabolic capabilities and role of metabolism in drug potentiation

Abstract

P. aeruginosa is an opportunistic human pathogen that is one of the leading causes of hospital-acquired infections. We have developed an updated genome-scale model (GEM) of Pseudomonas aeruginosa PA14 for systems-study of the pathogen. We used both automated and semi-manual approaches to reconstruct and curate the model. After an extensive literature research, we added organism-specific reactions (e.g., phenazine transport and redox metabolism, cofactor metabolism, carnitine metabolism, oxalate production, etc.) to the model. This effort led to a highly curated, three-compartment, and mass-and-charge balanced BiGG model of PA14 that contains 1509 genes, 1779 metabolic reactions and 1151 unique metabolites. The model (iSD1509) has the largest genome coverage of P. aeruginosa PA14 to date with 424 more genes than the previous model (iPau1129). It is also the most accurate with prediction accuracies as high as 92.4% (for gene essentiality) and 93.5% (for substrate utilization). The model simulates growth in both aerobic and anaerobic conditions. It predicts the biosynthesis of the virulence factor phenazine as a process for the pathogen to grow in low-oxygen environment. Further, a mechanism for the overproduction of a drug susceptibility biomarker (gluconate) can be elucidated by the principles of optimal growth. Finally, the model also simulates drug activity potentiation and protection by fumarate and glyoxylate, respectively, and provides mechanistic explanations for these processes. Overall, iSD1509 can be utilized to decipher the metabolic mechanisms associated with virulence and antibiotic susceptibility of P. aeruginosa PA14 to aid in the development of effective intervention strategies.