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Biology 2016, 5(2), 26; doi:10.3390/biology5020026

Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths

1
Core Research for Evolutionary Science and Technology (CREST), Japan Science and Technology Agency (JST), Okayama 700-0082, Japan
2
Graduate School of Natural Science and Technology, Okayama University, Okayama 700-0082, Japan
3
Department of Applied Chemistry, School of Advanced Engineering, Kogakuin University, Hachiohji, Tokyo 192-0015, Japan
4
Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA
5
Department of Chemical and Biological Science, Japan Woman’s University, Bunkyo-ku, Tokyo 112-8681, Japan
6
Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
7
Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
*
Authors to whom correspondence should be addressed.
Academic Editor: Jukka Finne
Received: 21 April 2016 / Revised: 26 May 2016 / Accepted: 27 May 2016 / Published: 3 June 2016
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Abstract

Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II) to Fe(III) and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II) concentrations, Fe(III) precipitates visibly formed immediately after addition of Fe(II) to the medium, suggesting prompt abiotic oxidation of Fe(II) to Fe(III). Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III) was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II) medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter), while those in the Fe(III) medium were composed of large, aggregated particles (≥3 µm diameter) with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved) of Fe encrustation of the Leptothrix sheaths. View Full-Text
Keywords: Leptothrix cholodnii SP-6; abiotic oxidation; Fe(III) particles; sheath; direct deposition Leptothrix cholodnii SP-6; abiotic oxidation; Fe(III) particles; sheath; direct deposition
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MDPI and ACS Style

Kunoh, T.; Hashimoto, H.; McFarlane, I.R.; Hayashi, N.; Suzuki, T.; Taketa, E.; Tamura, K.; Takano, M.; El-Naggar, M.Y.; Kunoh, H.; Takada, J. Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths. Biology 2016, 5, 26.

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