低温科学 = Low Temperature Science;第70巻

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結晶性酸化鉄を還元する土壌微生物群の同定と集積培養

堀, 知行

Permalink : http://hdl.handle.net/2115/49065

Abstract

鉄は地球上第四位の構成元素であり, 二価または三価の鉄鉱物として陸上土壌圏だけでなく海底地下圏にも広く分布している. そのため, 鉄の酸化還元に関与する微生物群は, 地球の炭素・エネルギーフラックスに重要な役割を果たしていると考えられる. 本稿では, 「結晶性酸化鉄を還元する土壌微生物群」に関する我々の研究を紹介する. まず初めに, 当該微生物群の発見に至った農耕地土壌(水田)における生物学的な鉄還元反応を簡単に概説する. 続いて, 分子生態学的手法Stable Isotope Probingを用い, 嫌気水田土壌で代謝活性を有する「結晶性酸化鉄の還元微生物群」を同定した実験について解説する. さらに, 様々な土壌試料を微生物接種源として用い, 結晶性酸化鉄を還元する微生物集積系を獲得した最近の試みを報告し, 最後に本書の主題である「アカシボ現象」の発生・発達に対する鉄還元微生物群の関与について考察したい.
Iron is the fourth most abundant element on earth and is distributed as forms of the ferrous and/or ferric iron minerals not only on the earth’s surface but also in the deep subseafloor. Thus, the microbes involved in the iron redox dynamics would play important roles in the carbon and energy fluxes on earth. In this article, we have reported our recent research activities with respect to soil microbes responsible for the reduction of crystalline iron(III) oxides. Prior to the experimental parts, we have briefly outlined the microbiological iron reduction processes in the agricultural paddy soils. At first, we have identified active, acetate-oxidizing, and iron(III)-reducing bacteria, including hitherto unrecognized populations, in anoxic rice field soils using RNAstable isotope probing. Secondly, we have obtained enrichment cultures of soil microbes that are able to reduce highly crystalline ferric iron minerals (e.g., hematite, magnetite, goethite, lepidocrocite) coupled with anaerobic acetate oxidation. Finally, we have discussed the involvement of the novel iron(III)-reducing bacteria in the formation and development of reddish-brown iron-rich snow (referred by locals as “Akashibo”) in Japanese alpine mires

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