Physiological and transcriptomic response of enriched anammox culture upon elevated hydrazine exposure.

Anammox has emerged as a cost-effective and eco-friendly biological treatment technology for high-strength wastewater, and hydrazine (NH) is a unique intermediate in the anammox metabolism. This study presents the first investigation into the genetic responses of anammox bacteria to elevated NH concentrations, offering critical insights into their potential for sustainable environmental applications. In this scope, anammox cultures were exposed to high levels of NH (up to 3 g/L) over a short-term period to evaluate their nitrogen treatment capacity and transcriptional responses. The results indicated that anammox activity continued at NH concentrations of 1.88 g/L or less. However, acute NH exposure significantly downregulated key genes, such as acetyl-CoA synthase beta and delta subunits, hydrazine synthase, hydrazine dehydrogenase, and hydroxylamine oxidoreductase, except for AAA family ATPase. Overall, high exogenous NH concentrations severely constrained the metabolism and survival of anammox bacteria at a molecular level. Understanding the genetic responses of anammox bacteria to elevated NH concentrations is crucial for optimizing their application in further anammox-based technologies. Future studies should focus on improving the resilience of anammox bacteria to high NH concentrations, thereby broadening their applicability in engineered wastewater treatment and biotechnological processes while maintaining system stability and efficiency.