Biotic acid mine drainage (AMD) suppression using lignin: Structure-activity relationship and molecular inactivation mechanism of inhibiting Acidithiobacillus ferrooxidans

Acid mine drainage (AMD) is a notorious environmental issue, and its economically and environmentally sustainable management remains challenging. A major driving force of AMD formation is the biooxidation of pyrite, largely mediated by acidophilic bacteria like Leptospirillum and Acidithiobacillus . Our previous study demonstrated that lignin can effectively inhibit pyrite oxidation by Acidithiobacillus ferrooxidans, thereby preventing AMD formation at the source. Building upon this, the current study investigated the structure-activity relationship of lignin in inhibiting A. ferrooxidans activity. Our findings indicated that low-molecular-weight lignin exhibits superior antibacterial activity, primarily through the induction of reactive oxygen species both intracellularly and extracellularly. Furthermore, transcriptomic analysis revealed that lignin influences critical bacterial pathways, including membrane biogenesis, carbohydrate metabolism, and signal transduction. This influence leads to an excessive consumption of the bacteria's internal carbon sources and disrupts their internal signal transduction system, ultimately inhibiting biofilm formation. This disruption culminates in cellular damage and bacterial cell death. Overall, this study offers technical guidance for selecting and preparing lignin with high antibacterial activity to enhance AMD control. It also sheds light on the molecular inactivation mechanism of lignin inhibiting A. ferrooxidans , providing a scientific basis for preventing acidification and supporting ecological restoration in new mining areas.