Energy-producing ability of bacteria under oxidative stress

Abstract

Nitrosative stress is caused by reactive nitrogen species (RNS) and is toxic to most organisms. RNS are generated by the immune system to combat infectious microbes and are known to impede O2-dependent energy production. The goal of this study was to elucidate alternative adenosine triphosphate (ATP)-forming pathways that enable the model bacterium Pseudomonas fluorescens to survive a nitrosative challenge in a fumarate medium. Fumarate was metabolized by fumarase C (FUM C), a RNS-resistant enzyme and fumarate reductase (FRD). The enhanced activities of pyruvate phosphate dikinase (PPDK), adenylated kinase (AK) and nucleoside diphosphate kinase (NDPK) provided an effective route to ATP production by substrate-level phosphorylation (SLP), a process that does not require O2. The metabolic networks utilized to neutralize nitrosative stress reveal potential target against RNS-tolerant bacteria and a route to the conversion of fumarate into succinate, a value-added product.