# Effects and Adaptive Responses of Sulfate-Reducing Biochemical System to Acid Stress

## TL;DR

This study explores how sulfate-reducing microbial systems adapt to acid stress, revealing physiological and genetic mechanisms that help them function in acidic environments.

## Contribution

The integration of microbial physiology and metagenomics reveals novel acid-adaptive mechanisms in sulfate-reducing consortia.

## Key findings

- The SRB system maintained sulfate removal efficiency under acid stress through physiological regulation.
- Acid-resistant bacteria like Bacillus and Clostridium enriched in the SRB system under low pH.
- Functional genes related to sulfate reduction and stress response were upregulated in the SRB system.

## Abstract

A decrease in pH can affect the biochemical properties of a sulfate reduction system, but the stress responses to such pH fluctuations and acid-adaptive mechanisms of the microorganisms remain incompletely understood. Here, we compared the sulfate (SO42−) reduction performance of a sulfate-reducing consortium (SRB system) and a pure Desulfovibrio sp. system (Des. system, control) under pH 7.0, 5.5, and 5.0 via batch experiments. A key novelty is the integration of microbial physiology and metagenomics to reveal adaptive mechanisms: the Des. system showed significant inhibition of growth and sulfate reduction with decreasing pH, while the SRB system maintained superior SO42− removal efficiency through three synergistic adjustments: (1) physiological regulation (enhanced H+-ATPase activity, stress protein production, and cell membrane cyclopropane fatty acid content); (2) microbial community restructuring (enrichment of acid-resistant Bacillus and Clostridium); and (3) functional gene upregulation (sulfate import, dissimilar sulfate reduction, sulfide oxidation, and SOx system-related genes, p < 0.05). This study links physiological responses to metagenomic functional shifts under acid stress, providing critical theoretical support for applying sulfate-reducing consortia in acidic sulfate-containing wastewater remediation.