Issue 16, 2013

Mechanisms of long-distance extracellular electron transfer of metal-reducing bacteria mediated by nanocolloidal semiconductive iron oxides

Abstract

Although nanocrystalline Fe(III) oxides are abundant in natural minerals, few studies have noticed their biological significance from the view point of semiconductive properties. To examine the roles of semiconductive Fe(III) oxides in the respiratory activity of microorganisms, we cultured the Fe(III)-reducing bacterium Shewanella loihica PV-4 in an electrochemical cell and examined the influence of cell surface-associated Fe-oxide nanocolloids on the extracellular electron transfer (EET) efficiency. It was found that the respiratory current was greatly improved (over 40 fold) when α-Fe2O3 or α-FeOOH was supplemented into the cell cultures. In contrast, only a small improvement (less than 4 fold) was observed after the addition of Fe3O4 and γ-Fe2O3. It was also found that the outer-membrane c-type cytochromes (c-Cyts) of Shewanella cells had a midpoint potential close to the conduction-band edge of α-Fe2O3 and α-FeOOH, whereas a large energy separation existed for γ-Fe2O3 and Fe3O4. These observations support the recently proposed model for bacterial long-distance EET (R. Nakamura, et al., Angew. Chem., Int. Ed., 2009, 48, 508–511), in which c-Cyts serve as electrical linkages between nanocolloids, allowing the cell population to exploit semiconductor-mediated electron-hopping. Support for this model was also provided by the mutational experiments of outer-membrane c-Cyts and the clear percolation behavior on the formation of conductive networks with respect to the amount of loaded colloids. Thus the EET mediated by semiconductive nanocolloids highlighted the microbial ability to take advantage of semiconductor-based electrochemistry for respiratory activities.

Graphical abstract: Mechanisms of long-distance extracellular electron transfer of metal-reducing bacteria mediated by nanocolloidal semiconductive iron oxides

Supplementary files

Article information

Article type
Paper
Submitted
28 дек 2012
Accepted
21 фев 2013
First published
21 фев 2013

J. Mater. Chem. A, 2013,1, 5148-5157

Mechanisms of long-distance extracellular electron transfer of metal-reducing bacteria mediated by nanocolloidal semiconductive iron oxides

R. Nakamura, F. Kai, A. Okamoto and K. Hashimoto, J. Mater. Chem. A, 2013, 1, 5148 DOI: 10.1039/C3TA01672B

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements