Deciphering direct interspecies electron transfer activity in microbial interactions: The influence of conductive materials in anoxic ecosystems

Direct interspecies electron transfer (DIET) stands as a cornerstone in anoxic ecosystems, facilitating electron exchange between partners without intermediates. However, a considerable gap persists in comprehensively elucidating how various materials promote DIET and interact with electroactive microbial species. To uncover the influence of different conductive materials on DIET-based anaerobic digestion systems, three carbon sources were used to simplify the microbial community and focus on exploring electroactive methanogens. Cyclic voltammetry results showed unique peaks in acetate-fed cultures with polyaniline-coated materials, highlighting the presence of DIET-active microbial species. CO₂-fed cultures with polyaniline-coated materials exhibited robust electrotrophic methanogenic activity in electrochemical cells. Additionally, cyclic voltammetry provided insights into electroactive biofilm stratification on conductive materials, allowing for a nuanced interpretation of microbiome responses. Comparative genomics showcased Desulfobulbaceae sp. DTU28 involvement in DIET through the identification of e-pilin. Furthermore, a putative e-pilin protein sequence with high aromatic amino acidic content was detected in Aminobacterium sp. DTU61. Co-occurrence analysis revealed potential syntrophic interactions between Methanosarcina sp. DTU142 and other species like Firmicutes sp. DTU111 and Bacteria sp. DTU118, indicating potential DIET-based cooperations. By analyzing electrochemical data and microbial genomic information, this study elucidated the impact of each material on DIET activity and characterized electroactive species, providing a deeper understanding of DIET-based microbial community interactions.