# Mechanisms underlying acid tolerance in Lysinibacillus sp. ND7, a highly efficient nitrate degrader

## TL;DR

A new strain of Lysinibacillus efficiently removes nitrate from acidic wastewater, offering potential for environmental cleanup.

## Contribution

The study identifies specific metabolic and proteomic mechanisms enabling acid tolerance and nitrate degradation in Lysinibacillus sp. ND7.

## Key findings

- ND7 achieved 80.70 ± 0.02% nitrate removal at pH 3.1.
- Metabolomics revealed enriched pathways for energy and stability under acidic conditions.
- Proteomic analysis showed up-regulated genes supporting nitrate removal and acid resistance.

## Abstract

In this study, the acid-tolerant strain Lysinibacillus sp. ND7 demonstrated excellent nitrate removal efficiency under acidic conditions, achieving a nitrate removal rate of 80.70 ± 0.02% in wastewater at pH 3.1. Metabolomics analysis revealed significant enrichment in pathways related to starch and sucrose metabolism, teichoic acid biosynthesis, and the phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS). These pathways play a crucial role in providing energy, regulating metabolism, and maintaining cellular stability during nitrate degradation. Proteomic analysis showed a significant up-regulation of genes involved in the nitrate removal pathway. Additionally, the up-regulation of ABC transporter protein genes and the down-regulation of genes involved in oxidative phosphorylation and electron transport worked together to support the nitrate metabolic pathway and help the strain resist acid stress. In conclusion, these findings underscore the impressive nitrate removal capacity of the novel strain ND7 and offer new insights into the mechanisms through which ND7 resists acid stress under acidic conditions.