  Pseudomonas aeruginosa is a metabolically flexible member of the
Gammaproteobacteria. Under anaerobic conditions and the presence of nitrate, P.
aeruginosa can perform (complete) denitrification, a respiratory process of
dissimilatory nitrate reduction to nitrogen gas via nitrite ($NO_{2}$), nitric
oxide ($NO$) and nitrous oxide ($N_{2}O$). This study focuses on understanding
the influence of environmental conditions on bacterial denitrification
performance, using a mathematical model of a metabolic network in P.
aeruginosa. To our knowledge, this is the first mathematical model of
denitrification for this bacterium. Analysis of the long-term behavior of the
network under changing concentration levels of oxygen ($O_{2}$), nitrate
($NO_{3}$), and phosphate ($PO_{4}$) suggests that $PO_{4}$ concentration
strongly affects denitrification performance. The model provides five
predictions on denitrification activity of P. aeruginosa under various
environmental conditions, and these predictions are either experimentally
validated or supported by pertinent biological literature. One motivation for
this study is to capture the effect of $PO_{4}$ on a denitrification metabolic
network of P. aeruginosa in order to shed light on mechanisms for greenhouse
gas $N_{2}O$ accumulation during seasonal oxygen depletion in aquatic
environments such as Lake Erie (Laurentian Great Lakes, USA).
