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Abstract <p><i>Acidithiobacillus thiooxidans</i> is an extremophilic bacterium adapted to highly acidic, metal-rich environments. While its role in extracellular electron transfer (EET) has gained interest, the contribution of type IV pilins (T4P) remains poorly understood. In this study, we electrochemically characterized two recombinant pilins from <i>A. thiooxidans</i>, PilA (major) and PilV (minor), to explore their potential involvement in redox activity. Using a three-electrode electrochemical setup, PilV displayed a distinct anodic response at ~0.95 V with a peak current of ~75 µA, indicating high redox responsiveness. In contrast, PilA showed a broader oxidation range (0.55–1.1 V) and a weaker signal (~50 µA). These differences correlate with the surface accessibility of electroactive amino acids (EAAs), particularly tyrosine. Structural modeling revealed that while both pilins contain aromatic residues, in PilA they are partially buried within an α-helix, whereas in PilV they are more exposed in the globular domain. This spatial arrangement likely enhances PilV’s capacity for direct electron transfer. Altogether, our findings suggest that PilV’s structure is better suited for redox coupling with solid surfaces, supporting its potential role in EET and highlighting its relevance in future studies of microbial electron transport in extreme environments.</p>

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Electrochemical Properties of PilA and PilV Pilins from Acidophile Acidithiobacillus thiooxidans

  • 期刊论文

  • 发表日期：

    2026年1月1日

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  • Elvia Alfaro-Saldaña,
  • Edgar D. Páez-Pérez,
  • Nehemías Leija,
  • J. Viridiana García-Meza

摘要

Abstract

Acidithiobacillus thiooxidans is an extremophilic bacterium adapted to highly acidic, metal-rich environments. While its role in extracellular electron transfer (EET) has gained interest, the contribution of type IV pilins (T4P) remains poorly understood. In this study, we electrochemically characterized two recombinant pilins from A. thiooxidans, PilA (major) and PilV (minor), to explore their potential involvement in redox activity. Using a three-electrode electrochemical setup, PilV displayed a distinct anodic response at ~0.95 V with a peak current of ~75 µA, indicating high redox responsiveness. In contrast, PilA showed a broader oxidation range (0.55–1.1 V) and a weaker signal (~50 µA). These differences correlate with the surface accessibility of electroactive amino acids (EAAs), particularly tyrosine. Structural modeling revealed that while both pilins contain aromatic residues, in PilA they are partially buried within an α-helix, whereas in PilV they are more exposed in the globular domain. This spatial arrangement likely enhances PilV’s capacity for direct electron transfer. Altogether, our findings suggest that PilV’s structure is better suited for redox coupling with solid surfaces, supporting its potential role in EET and highlighting its relevance in future studies of microbial electron transport in extreme environments.