Extracellular electron transfer through visible light induced excited-state outer membrane C-type cytochromes of Geobacter sulfurreducens

• Published in: Bioelectrochemistry (Amsterdam, Netherlands) Vol. 138; p. 107683
• Main Authors: Zhang, Bo, Cheng, Hao-Yi, Wang, Aijie
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.04.2021; Elsevier BV
• Subjects: Bioelectrochemical systems; Coated electrodes; Conduction bands; Cytochrome; Cytochromes; Dissimilatory metal-reducing bacteria; Electrochemistry; Electron states; Electron transfer; Electrons; Excitation; Excitation spectra; Excited-state; Extracellular electron transfer; Geobacter sulfurreducens; Illumination; In vivo methods and tests; Light; Membranes; Photoelectrochemical; Spectroscopy; TiO2; Titanium dioxide; Bioelectrochemical systems; Extracellular electron transfer; Excited-state; Dissimilatory metal-reducing bacteria; Photoelectrochemical; TiO2; TiO
• ISSN: 1567-5394; 1878-562X; 1878-562X
• DOI: 10.1016/j.bioelechem.2020.107683

[Display omitted] •Visible light can excite outer membrane c-type cytochrome of G. sulfurreducens.•Excited cytochromes have more negative potentials compared to ground-state ones.•G. sulfurreducens can perform electron transfer using excited cytochromes. 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.