The excellent performance of biosemiconductors in solar energy conversion and environmental remediation has triggered an explosive research in recent years. However, there is still a lack of knowledge on the mechanisms of extracellular photoelectron uptake in biosemiconductors, especially for the denitrifier-based one. Herein, a model biosemiconductor, Thiobacillus denitrificans-cadmium sulfide (T. denitrificans-CdS), for photoelectrotrophic denitrification was used to investigate the mechanism. Electrochemical characterization demonstrated more redox species generation after exposing T. denitrificans-CdS to light than the controls. Photoelectron uptake process was in situ recorded by an ITO-bottom electrochemical reactor. UV–Vis spectroscopy assured more outer-membrane cytochrome c generation and its concentration was 3.35 times higher in the light than that at dark. A coupled technology of SDS–PAGE, heme staining and LC–MS/MS targeted periplasmic cytochrome c₄ (Cyt c₄) emerging in T. denitrificans-CdS (light). Moreover, the expression of the cyt c₄ gene was significantly (p < 0.05) upregulated under light, and its abundance increased from 1.2 ± 0.3 to 4.7 ± 1.2 folds with light intensity changing from 0.5 to 2.0 mW cm⁻², supporting its role in the photoelectron uptake process. This work revealed the photoelectron uptake mechanism in T. denitrificans-CdS, and the results will provide guidance for constructing an efficient biosemiconductor system for nitrate removal and conversion driven by light.

近年来，生物半导体在太阳能转换和环境修复方面的优异性能引发了爆炸性的研究。然而，对于生物半导体中细胞外光电子摄取的机制仍然缺乏了解，尤其是基于反硝化的生物半导体。在此，使用模型生物半导体，脱氮硫杆菌- 硫化镉（T. denitrificans -CdS），用于光电营养反硝化作用来研究其机制。电化学表征表明，在将反硝化杆菌-CdS暴露于光照后，产生的氧化还原物质比对照多。原位光电子吸收过程由 ITO 底部电化学反应器记录。紫外-可见光谱确保了更多的外膜细胞色素c的产生，其浓度在光照下比在黑暗下高 3.35 倍。SDS-PAGE、血红素染色和 LC-MS/MS 的耦合技术靶向出现在T. denitrificans -CdS（光）中的周质细胞色素c ₄ (Cyt c _{4 )。}此外， cyt c ₄基因的表达在光照下显着上调 (p < 0.05)，其丰度从 1.2 ± 0.3 增加到 4.7 ± 1.2 倍，光照强度从 0.5 到 2.0 mW cm ^-2，支持其在光电子摄取过程中的作用。该工作揭示了T. denitrificans -CdS的光电子摄取机制，该结果将为构建高效的光驱动硝酸盐去除和转化生物半导体系统提供指导。