Hemin-binding DNA structures on the surface of bacteria promote extracellular electron transfer.

Non-canonical DNA structures have been recently identified in bacterial biofilms, but their functional roles remain poorly understood. Here, we demonstrate that G-quadruplex (G4) DNA structures complexed with hemin enable extracellular electron transfer (EET) in biofilms. Using Staphylococcusepidermidis as a model organism, we show that extracellular DNA and hemin are essential for EET, with surface-associated G4-DNA/hemin complexes transferring electrons from bacteria to electrodes under anoxic conditions. Adding G4-DNA and hemin to growing biofilms promoted stable EET for days, demonstrating that these complexes serve as robust electrical conduits. The structural properties of G4-DNA, with its stacked guanine quartets facilitating π-π interactions with hemin's porphyrin ring, create an effective electron transfer pathway. Additionally, the G4-DNA/hemin complex functions as a peroxidase-like DNAzyme, transferring electrons from bacteria to H2O2. This study reveals a previously unknown functional role for G4-DNA structures in biofilms, establishing them as components of bacterial EET. Our findings provide new insights into how non-canonical DNA structures contribute to bacterial energy conservation under oxygen limitation, and potentially also to their defense against oxidative stress during infection.