Dissimilatory metal-reducing bacteria (DMRB) have a variety of c-type cytochromes (OM c-cyts) intercalated in their outer membrane, and this structure serves as the physiological basis for DMRB to carry out the extracellular electron transfer processes. Using Geobacter sulfurreducens as a model DMRB, we demonstrated that visible-light illumination could alter the electronic state of OM c-cyts from the ground state to the excited state in vivo. The existence of excited-state OM c-cyts in vivo was confirmed by spectroscopy. More importantly, excited-state OM c-cyts had a more negative potential compared to their ground-state counterparts, conferring DMRB with an extra pathway to transfer electrons to semi-conductive electron acceptors. To demonstrate this, using a TiO₂-coated electrode as an electron acceptor, we showed that G. sulfurreducens could directly utilise the conduction band of TiO₂ as an electron acceptor under visible-light illumination (λ > 420 nm) without causing TiO₂ charge separation. When G. sulfurreducens was subject to visible-light illumination, the rate of extracellular electron transfer (EET) to TiO₂ accelerated by over 8-fold compared to that observed under dark conditions. Results of additional electrochemical tests provided complementary evidence to support that G. sulfurreducens utilised excited-state OM c-cyts to enhance EET to TiO₂.

异化金属还原细菌（DMRB）在其外膜中插入了多种c型细胞色素（OM c-cyts），这种结构为DMRB进行细胞外电子转移过程提供了生理基础。使用还原性地球细菌作为模型DMRB，我们证明了可见光照射可在体内将OM c-细胞的电子状态从基态变为激发态。体内兴奋态OM c细胞的存在由光谱证实。更重要的是，与基态对应物相比，激发态OM c-细胞具有更大的负电势，这为DMRB提供了将电子转移至半导体电子受体的额外途径。为了证明这一点，使用涂有TiO ₂的电极作为电子受体，我们证明了G.sulfreducens可以在可见光（λ> 420 nm）下直接利用TiO ₂的导带作为电子受体，而不会引起TiO ₂电荷分离。当硫还原还原杆菌受到可见光照射时，细胞外电子转移（EET）向TiO ₂的速率与黑暗条件下观察到的相比，加速了8倍以上。其他电化学测试的结果提供了补充证据，以支持硫还原菌利用激发态OM c-cyts增强EET对TiO _2的作用。