微生物がニッケルの必要性を減らすことが可能であることを発見(Microbes can reduce their need for nickel)

2025-07-02 マックス・プランク研究所(MPI)

Methanogenic archaea have a major impact on the global climate, as they produce almost all naturally occurring methane. They are usually cultivated and studied under nutrient-rich conditions, especially at high nickel concentrations. A research team led by Dr Seigo Shima at the Max Planck Institute for Terrestrial Microbiology has now investigated methanogenesis under nutrient-poor conditions and discovered a strategy that microbes can use to reduce their nickel requirements.　© MPI f. terrestrische Mikrobiologie/ Nomura&Geisel

<関連情報>

• https://www.mpg.de/25007143/microbes-can-reduce-their-need-for-nickel
• https://www.nature.com/articles/s41586-025-09229-y

ニッケル制限下における水素栄養メタン菌の電子の流れ Electron flow in hydrogenotrophic methanogens under nickel limitation

Shunsuke Nomura,Pablo San Segundo-Acosta,Evgenii Protasov,Masanori Kaneko,Jörg Kahnt,Bonnie J. Murphy & Seigo Shima
Nature  Published:02 July 2025
DOI:https://doi.org/10.1038/s41586-025-09229-y

Abstract

Methanogenic archaea are the main producers of the potent greenhouse gas methane^1,2. In the methanogenic pathway from CO₂ and H₂ studied under laboratory conditions, low-potential electrons for CO₂ reduction are generated by a flavin-based electron-bifurcation reaction catalysed by heterodisulfide reductase (Hdr) complexed with the associated [NiFe]-hydrogenase (Mvh)^3,4,5. F₄₂₀-reducing [NiFe]-hydrogenase (Frh) provides electrons to the methanogenic pathway through the electron carrier F₄₂₀ (ref. ⁶). Here we report that under strictly nickel-limited conditions, in which the nickel concentration is similar to those often observed in natural habitats^7,8,9,10,11, the production of both [NiFe]-hydrogenases in Methanothermobacter marburgensis is strongly downregulated. The Frh reaction is substituted by a coupled reaction with [Fe]-hydrogenase (Hmd), and the role of Mvh is taken over by F₄₂₀-dependent electron-donating proteins (Elp). Thus, Hmd provides all electrons for the reducing metabolism under these nickel-limited conditions. Biochemical and structural characterization of Elp–Hdr complexes confirms the electronic interaction between Elp and Hdr. The conservation of the genes encoding Elp and Hmd in CO₂-reducing hydrogenotrophic methanogens suggests that the Hmd system is an alternative pathway for electron flow in CO₂-reducing hydrogenotrophic methanogens under nickel-limited conditions.