熱水噴出孔による92°Cの窒素固定 archaeon
Mausmi P Mehta1, John A Baross
1School of Oceanography, University of Washington, Seattle, WA 98195, USA. mausmi@alum.mit.edu
まとめ
科学者たちは,生物学的窒素を92°Cで固定することができる超熱性アーケオンを発見し,極端な環境でこの重要なプロセスのための既知の温度限界を拡大しました.
科学分野:
- 微生物学 微生物学とは
- バイオケミストリー バイオケミストリー
- エクストレモフィルの研究
背景:
- 生物学的窒素固定は生命にとって不可欠であり,大気中の窒素 (N2) をアンモニア (NH3) に変換する.
- 生物学的窒素固定の既知の上限温度は,以前は64°Cであった.
- 深海の熱水噴出孔は,極端な温度と圧力に適応したユニークな微生物群を宿している.
研究 の 目的:
- 超熱性微生物における生物学的窒素固定の可能性を調査する.
- 深海の熱水噴出孔からの新しい窒素固定生物を特定し,特徴づけること.
- 窒素固定の温度上限を決定するために.
主な方法:
- 深海の熱水噴出液から微生物の分離と培養.
- 系統遺伝分析のための16SリボソームRNA遺伝子配列決定.
- イソトープラベリング ((15) N2) を用いて窒素固定活動の測定.
- メッセンジャーRNA検出による窒素酶遺伝子 (nifH) 発現の分析.
主要な成果:
- 新しいメタノゲン系アーケオンであるFS406-22は,深海の熱水噴出液から分離されました.
- FS406-22は92°Cまでの温度で窒素固定 (N2からNH3への還元) を実証した.
- この温度は,生物学的窒素固定のための以前に確立された上限よりも28°C高い.
- 系統遺伝学的分析により,FS406-22は,Methanocaldococcus jannaschii.と密接に関連していることが示されました (99%の16S rRNA類似性).
- FS406-22は,90°Cの最適な成長温度で,15N2を組み込み,nifHmRNAを発現させた.
結論:
- FS406-22の発見は,生物学的窒素固定のための既知の温度範囲を大幅に拡張しています.
- この発見は,地底下部生物圏における生命と窒素循環のためのより広い可能性を示唆しています.
- これは,窒素に限られた生態系が,極端な暑さ下でも,生物学的窒素固定を支える可能性があることを示唆しています.
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