A New Electron Shuttling Pathway Mediated by Lipophilic Phenoxazine via the Interaction with Periplasmic and Inner Membrane Proteins of Shewanella oneidensis MR-1

Abstract

Although it has been established that electron mediators substantially promote extracellular electron transfer (EET), electron shuttling pathways are not fully understood. Here, a new electron shuttling pathway was found in the EET process by Shewanella oneidensis MR-1 with resazurin, a lipophilic electron mediator. With resazurin, the genes encoding outer-membrane cytochromes (mtrCBA and omcA) were downregulated. Although cytochrome deletion substantially reduced biocurrent generation to 1−12% of that of wild-type (WT) cells, the presence of resazurin restored biocurrent generation to 168 μA•cm −2 (ΔmtrA/ omcA/mtrC), nearly equivalent to that of WT cells (194 μA•cm −2 ), indicating that resazurin-mediated electron transfer was not dependent on the Mtr pathway. Biocurrent generation by resazurin was much lower in ΔcymA and ΔmtrA/omcA/mtrC/fccA/cctA mutants (4 and 6 μA•cm −2 ) than in WT cells, indicating a key role of FccA, CctA, and CymA in this process. The effectiveness of resazurin in EET of Mtr cytochrome mutants is also supported by cyclic voltammetry, resazurin reduction kinetics, and in situ c-type cytochrome spectroscopy results. The findings demonstrated that low molecular weight, lipophilic electron acceptors, such as phenoxazine and phenazine, may facilitate electron transfer directly from periplasmic and inner membrane proteins, thus providing new insight into the roles of exogenous electron mediators in electron shuttling in natural and engineered biogeochemical systems.

Electrochemical Additive Manufacturing of Living Bioelectrodes Having Intimate Electronic Couplings between Exoelectrogens and Electrodes

“…For instance, S. oneidensis MR‐1, a Gram‐negative bacterium, excels in extracellular electron transfer facilitated by specialized outer membrane cytochromes for direct contact transfer. [ 35 ] On the contrary, B. subtilis , a Gram‐positive bacterium found in soil and the gastrointestinal tract produces flavins that serve as effective electron shuttles. The flavins can transfer electrons to extracellular electron acceptors, enabling B. subtilis to participate in redox reactions and potentially interact with external electrodes for relatively long‐range electron transfer.…”

Efficient Enhancement of Extracellular Electron Transfer in Shewanella oneidensis MR-1 via CRISPR-Mediated Transposase Technology

“…Previous research has demonstrated that PCA can enhance EET capacity in both Escherichia coli and MR-1 species. 10,29 In this study, a gene cluster consisting of seven related genes, phzA1-G1, was successfully transferred from P. aeruginosa into the MR-1 genome under the control of an arabinose-inducible promoter (Figure 3A). The cargo gene was replaced with an 8.2 kb fragment containing the PCA synthesis gene cluster in p-INTEGRATE.…”

Enhanced photocatalytic CO2reduction on biomineralized CdSviaan electron conduit in bacteria

“…When SW@CdS was used, it also changed to the original color of the photocatalyst (yellow), which suggests a microbial electron shuttling process and the successful formation of an anaerobic environment. 53 The quantity of the generated H 2 O 2 for the SW@CdS and CdS photocatalysts was determined by iodometry. The amount of H 2 O 2 produced after four-hour illumination was 0.96 μM, which was slightly lower than that of chemosynthetic CdS (1.61 μM) and much lower than the reported value for photocatalysts used for producing hydrogen peroxide (Fig.…”