Semiconducting Minerals Participated Extracellular Electron Transfer Process in High-Altitude Red Soil from Gansu, China

Abstract

The microbial extracellular electron transfer (EET) process plays an important role in biogeochemistry. Here, semiconducting minerals that participated in EET in high-altitude red soil were investigated for the first time. Semiconducting minerals and microbial communities were analyzed by XRD and 16S rRNA, respectively. The photoresponse and semiconducting mineral properties of red soil were characterized by linear sweep voltammetry (LSV) and I–t curves, and well synchronous light-response properties were observed. Then, the EET process without light was explored in a dual-chamber system, the maximum power density of red soil cathode was nearly two times higher than graphite cathode, indicated that mineral serving as electron acceptor. Under light irradiation, the highest photo-current density (3.939 μA/cm2) was observed between red soil electrode and live bacteria, indicating the microbial EET process was significantly enhanced. Furthermore, electrochemical impedance spectroscopy (EIS) was employed to investigate the mechanism, results showed that the interface charge transfer resistance (Rct) of red soil electrode was obviously reduced from 396 to 316 Ω under light conditions. This study demonstrated that semiconducting minerals could participate microbial EET process via sunlight catalysis in high-altitude environments.