Involvement of microaerophilic iron-oxidizing bacteria in the iron-oxidizing process at the surface layer of flooded pad
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SOILS, SEC 5 • SOIL AND LANDSCAPE ECOLOGY • SHORT ORIGINAL COMMUNICATION
Involvement of microaerophilic iron-oxidizing bacteria in the iron-oxidizing process at the surface layer of flooded paddy field soil Koki Nakagawa 1 & Jun Murase 2 & Susumu Asakawa 2 & Takeshi Watanabe 2 Received: 10 May 2020 / Accepted: 8 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose To reveal whether microaerophilic Fe(II)-oxidizing bacteria (FeOB) participate in the Fe(II) oxidation at the oxic-anoxic interface in flooded paddy field soil, distribution of microaerophilic FeOB belonging to Gallionellaceae (Gallionella-related FeOB) in the surface layer of a flooded paddy soil microcosm and O2 conditions for the Fe(II) oxidation by a microaerophilic Fe(II) oxidizer, Ferrigenium kumadai An22, were investigated. Materials and methods Flooded paddy soil microcosms were incubated for 30 days. Five soil layers were sampled at 2-mm intervals from the soil surface after the incubation. The community structure of Gallionella-related FeOB was analyzed with qPCR and DGGE methods. In the culture experiment, O2 and Fe(II) profiles in F. kumadai An22-inoculated and non-inoculated gel-stabilized gradient tubes were analyzed, in which an opposing gradient of O2 and Fe(II) was formed. Results A thin oxic layer was formed at the soil surface after the incubation. The copy number of 16S rRNA genes of Gallionellarelated FeOB was highest at the top 0–2 mm layer of the soil. DGGE analysis showed that several bands derived from Gallionella-related FeOB newly appeared at the top soil layer with high intensity. In the culture experiment, F. kumadai A22 grew at the oxic side of the oxic-anoxic interface with the formation of Fe oxides. Conclusion The present study indicated that Gallionella-related microaerophilic FeOB proliferated in the surface layer of flooded paddy field soil, presumably by oxidizing Fe(II) in the oxic-anoxic interface. Keywords Microaerophile . Iron-oxidizing bacteria . O2 profile . Oxic-anoxic interface . Paddy field soil
1 Introduction The redox cycle of iron (Fe) is the central process in the biogeochemistry of paddy fields. The fluctuation of the redox status of Fe between Fe(II) and Fe(III) influences not only the pH and redox potential in the soil (Kyuma 2004) but also the dynamics of organic and inorganic substances (Li et al. Responsible editor: Jizheng He Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11368-020-02717-w) contains supplementary material, which is available to authorized users. * Takeshi Watanabe [email protected] 1
School of Agricultural Sciences, Nagoya University, Chikusa Nagoya 464-8601 Japan
2
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa Nagoya 464-8601 Japan
2012). The redox cycle of Fe in various environments is mediated via abiotic and biotic reactions, in which microaerophilic, phototrophic, and nitrate-reducing Fe(II)-oxidizing bacteria (FeOB) mediate the biotic reactions in circu
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