Nitrate removal by acid-tolerant Fictibacillus phosphorivorans MJ9 in acidic anaerobic environments

Abstract

In this study, an acid-tolerant strain, Fictibacillus phosphorivorans MJ9, demonstrated exceptional nitrate removal efficiency under acidic conditions. It achieved 80.4 ± 1.1% nitrate degradation at an initial pH of 3.1. Metabolomic and proteomic analyses suggest that nitrate reduction by strain MJ9 primarily occurs via dissimilatory nitrate reduction to ammonium (DNRA) and partial denitrification, accompanied by incomplete denitrification. In addition, key metabolic processes—including glycolysis, fatty acid metabolism, purine metabolism, and the tricarboxylic acid (TCA) cycle—play essential roles in supplying energy, regulating metabolic fluxes, and maintaining cellular homeostasis. Collectively, these findings underscore the remarkable nitrate removal capability of the novel strain MJ9 and provide valuable insights into its metabolic adaptations under anaerobic and acidic conditions.