報告書番号

U99051

タイトル（和文）

電気による微生物の制御 (その５) --嫌気鉄呼吸を利用した微生物の電気培養--

タイトル（英文）

Electrochemical cultivation of bacteria on anaerobic iron respiration

概要 （図表や脚注は「報告書全文」に掲載しております）

鉄酸化細菌は酸素がない場合、水素を酸化して３価鉄を２価鉄に還元する無酸素的な鉄呼吸によりエネルギーを獲得して生育し、この無酸素鉄呼吸はC型チトクロムにより仲介されることが分かった。通電しながら鉄酸化細菌を無酸素条件で培養したところ、細菌は３価鉄を２価鉄に還元する無酸素的な鉄呼吸を行い、電気によって２価鉄を３価鉄に酸化して細菌の呼吸を促進できた。その結果、細菌と電極との間に鉄を媒体として電気が流れ、通電しない場合の１０倍まで生育量が増加した。電気の媒体に鉄を使って無酸素呼吸を促進する新しい電気培養が立証できた。

概要 （英文）

Electrochemical control of microorganisms Part 5Electrochemical cultivation of bacteria on anaerobic iron respirationNaoya Ohmura, Norio Matsumoto, Kazuhiro Sasaki and Hiroshi Saiki.We are developing electrolytic cultivation to open new technologies for production of chemicals and/or environmental remediation using bacteria. It succeeded in previous investigations to culture the bacteria, which take energy for growth from the oxidation of ferrous ions to ferric ions. The growth was stimulated by continuous supply of ferrous ions through the electrolytic reduction of ferric ions. The stimulation of aerobic respiration by electrolysis, it was possible to culture the cells at high densities. However, this electrolytic cultivation is only useful for bacteria, which can respire aerobically on iron. Another approach is necessary to open the new use of the electrolytic procedure to culture many bacteria.Bacteria use cellular respiration to convert energy stored in the chemical bonds of substrates to a form usable by the cells, a process which entails the transfer of electrons from donors to acceptors along a respiratory chain. We therefore hypothesized that if an electrode could be employed as the terminal electron acceptor, it might be possible to artificially control the respiratory electron flow supporting the energy for bacterial growth. Here we describe our use of such a system to regulate electrolytic respiration and thus growth in Thiobacillus ferrooxidans. Anaerobic respiration using Fe(III) as an electron acceptor and H2 as an electron donor serves as a primary energy source for anaerobic growth of the bacterium. Such anaerobic respiration induced T. ferrooxidans to synthesize significant amounts of C-type cytochrome which then served as an electron donor for reduction of Fe(III). Respiration based on reduction of Fe(III) coupled to oxidation of C-type cytochrome is the primary mechanism of energy production. This anaerobic iron respiration was enhanced to stimulate the anaerobic growth of the bacterium under the electrolytic cultivation. The cathode served as the terminal electron acceptor for anaerobic respiration, while H2 served as the electron donor. The electron flow from H2 to the cathode was mediated by iron, which shuttled electrons between the cells and the cathode, enabling bacterial cultures to reach a density of 1010 cells/ml. Such electrolytic cultivation may be a potentially productive strategy for cultivating not only known bacteria not only as yet undiscovered iron reducers.

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