Sulfate-reducing bacteria in acid mine drainage: ecological constraints, microbial networks, and functional...

Sulfate-reducing bacteria (SRB) are key functional microorganisms in the bioremediation of acid mine drainage (AMD), simultaneously removing sulfate, generating alkalinity, and precipitating metal sulfides via dissimilatory sulfate reduction. AMD is typically characterized by low pH, high sulfate and metal concentrations, and limited organic carbon, imposing persistent stress on SRB growth, metabolism, and function. Environmental stressors include acidic conditions, heavy metal toxicity, low-temperature stress, and electron-donor limitation. These stressors impair membrane stability, enzymatic activity, and cellular energy conservation. Their combined effects increase maintenance requirements while limiting energy acquisition, ultimately reducing the range of environmental conditions under which SRB can sustain sulfate reduction. At the community level, SRB function is further modulated by complex microbial networks. Various functional groups, including fermenters, methanogens, and sulfur- and iron-cycling microorganisms, interact with SRB through cooperative, competitive, and regulatory processes that influence electron transfer, carbon turnover, and iron-sulfur transformations. Sulfate reduction in AMD depends on these community-level interactions, which can be disrupted under environmental stress and may reduce the stability of sulfate-reducing communities. Engineering strategies such as slow-release carbon supplementation, pH microenvironment optimization, conductive material amendment, mineral-microbe interface regulation, and immobilized reactor design can enhance SRB persistence by stabilizing the extracellular microenvironment, regulating electron flow, and spatially decoupling metabolic and mineralization interfaces. This review highlights how environmental stressors and microbial networks jointly regulate SRB function, emphasizes the roles of metabolic niche constraints and community resilience, and provides mechanistic insights for improving the stability and practical performance of SRB-based AMD treatment systems.