- 著者
- Akihiro Okamoto Yoshihide Tokunou Junki Saito
- 出版者
- 一般社団法人 日本生物物理学会
- 雑誌
- Biophysics and Physicobiology (ISSN:21894779)
- 巻号頁・発行日
- vol.13, pp.71-76, 2016 (Released:2016-05-27)
- 参考文献数
- 32
- 被引用文献数
- 11
Outer-membrane c-type cytochrome (OM c-Cyt) complexes in several genera of iron-reducing bacteria, such as Shewanella and Geobacter, are capable of transporting electrons from the cell interior to extracellular solids as a terminal step of anaerobic respiration. The kinetics of this electron transport has implications for controlling the rate of microbial electron transport during bioenergy or biochemical production, iron corrosion, and natural mineral cycling. Herein, we review the findings from in-vivo and in-vitro studies examining electron transport kinetics through single OM c-Cyt complexes in Shewanella oneidensis MR-1. In-vitro electron flux via a purified OM c-Cyt complex, comprised of MtrA, B, and C proteins from S. oneidensis MR-1, embedded in a proteoliposome system is reported to be 10- to 100-fold faster compared with in-vivo estimates based on measurements of electron flux per cell and OM c-Cyts density. As the proteoliposome system is estimated to have 10-fold higher cation flux via potassium channels than electrons, we speculate that the slower rate of electron-coupled cation transport across the OM is responsible for the significantly lower electron transport rate that is observed in-vivo. As most studies to date have primarily focused on the energetics or kinetics of interheme electron hopping in OM c-Cyts in this microbial electron transport mechanism, the proposed model involving cation transport provides new insight into the rate detemining step of EET, as well as the role of self-secreted flavin molecules bound to OM c-Cyt and proton management for energy conservation and production in S. oneidensis MR-1.
- 著者
- Shu ZHANG Waheed MIRAN Divya NARADASU Siyi GUO Akihiro OKAMOTO
- 出版者
- The Electrochemical Society of Japan
- 雑誌
- Electrochemistry (ISSN:13443542)
- 巻号頁・発行日
- pp.20-00021, (Released:2020-04-21)
- 参考文献数
- 34
- 被引用文献数
- 9
Microbial extracellular electron transfer (EET) in diverse environments has gained increasing attention. However, the EET capability of oral pathogens and associated mechanisms has been scarcely studied. Here, our results suggest that the Capnocytophaga ochracea, an etiological human pathogen showed current production and demonstrated a rate enhancement of electron transport at a high cell-density. C. ochracea produced ∼10-fold more current at an OD600 of 0.5 associated with twice a higher glucose consumption rate per cell, compared to 0.1, measured in a three-electrode electrochemical system by single-potential amperometry at +0.2 V (vs Ag/AgCl [sat. KCl]). During current production, the accumulation of the redox molecules on the electrode was observed at high OD600 compared to low OD600. Apart from cell released redox active product, externally added redox active additives enhanced the electron transport, suggesting the EET capability of C. ochracea via electron mediator. A higher metabolic activity via single-cell assay (based on anabolic incorporation of 15NH4+) in cells that did not attach to the electrode strongly suggests the EET rate enhancement through an electron mediator. As bacterial populations play a role in the pathogenesis of human infections such as periodontitis, our results suggest that population-induced EET mechanisms may facilitate in-vivo colonization of C. ochracea.
- 著者
- Xiao DENG Ryuhei NAKAMURA Kazuhito HASHIMOTO Akihiro OKAMOTO
- 出版者
- 公益社団法人 電気化学会
- 雑誌
- Electrochemistry (ISSN:13443542)
- 巻号頁・発行日
- vol.83, no.7, pp.529-531, 2015-07-05 (Released:2015-07-05)
- 参考文献数
- 12
- 被引用文献数
- 3 40
We report that an intensely iron-corroding microbe, Desulfovibrio ferrophilus strain IS5, is capable of extracting electrons from an indium tin-doped oxide electrode without consuming electrochemically generated hydrogen as an electron carrier. When sulfate was presented as a metabolic electron acceptor, significant cathodic current production was observed at an onset potential of −200 mV vs. SHE, which was approximately 750 mV more positive than the onset for hydrogen evolution in our experimental condition. This finding indicates that hydrogen is not required for the cathodic reaction of IS5, suggesting that IS5 accelerates anaerobic iron corrosion through direct electron uptake.