Nano-bio interfaces as regulators of bacterial electron metabolism: from extracellular electron transfer to community-scale electron networks.

Nanomaterial-bacterium interactions are commonly interpreted through antibacterial mechanisms such as reactive oxygen species generation, photothermal effects, membrane disruption and ion toxicity. However, under nonlethal or sublethal conditions, nano-bio interfaces can also regulate bacterial electron metabolism by reshaping extracellular electron dissipation, interfacial charge transfer, charge-transfer resistance (Rct), redox buffering and biofilm-associated electron networks. Here, we propose a functional framework that views bacterial metabolism as an integrated process of electron generation, interfacial transfer and electron dissipation. Within this framework, nanomaterials are classified by their positions in bacterial electron-flow networks as electron sinks, electron relays or electron buffers. We further distinguish beneficial coupling from electron hijacking by determining whether enhanced interfacial electron transfer is coupled to NADH/NAD+ balance, ATP production, membrane-potential maintenance and productive carbon-flux redistribution, or instead leads to futile electron loss, oxidative damage and energetic collapse. Extending this view from single cells to extracellular polymeric substances (EPS), electroactive biofilms and direct interspecies electron transfer (DIET), we discuss how nano-bio interfaces re-gate microbial electron flow at the community scale. This Review shifts the focus from how nanomaterials kill bacteria to how they reprogram microbial redox boundaries, providing a conceptual basis for antibacterial interface design, biofilm control, microbial sensing, biomanufacturing and microbiome engineering.