最新のアルケア紀における有酸素窒素循環の同位体証拠
Jessica Garvin1, Roger Buick, Ariel D Anbar
1Department of Earth and Space Sciences and Astrobiology Program, University of Washington, Seattle, WA 98195-1310, USA.
まとめ
古代の微生物は,大気中の酸素より先に窒素循環を進化させた. この研究は,25億年前の岩石における窒素化と脱窒素化の証拠を明らかにし,広範囲にわたる酸素化以前のものである.
科学分野:
- 地質化学 地質化学
- パレオバイオロジーの古生物学
- 環境科学 環境科学
背景:
- 窒素循環は生命にとって不可欠ですが,その進化の歴史,特にその現代的な形態は不明のままです.
- 初期の窒素循環の理解は,初期の地球環境と微生物の生命の進化の洞察を提供します.
研究 の 目的:
- 窒素化と脱窒化を含む,現代の窒素循環の古さを調査する.
- これらのプロセスが大気中の酸素の蓄積前に活発であったかどうかを判断する.
主な方法:
- マウント・マクレイ・シェイルの25億年前の掘削コアにおける窒素同位体値の分析.
- モリブデンと硫黄の同位体値の補足分析.
主要な成果:
- 窒素同位体値は,約30メートルで有意な変動 (+1.0〜+7.5 per mil) を示した.
- これらの変動は,無酸素から有酸素窒素サイクルへの一時的なシフトを示しています.
- モリブデンと硫黄のイソトープは,このシフトは,表面と海洋の酸素化の増加に関連していることを示唆しています.
結論:
- 窒素化および非窒素化する微生物は,アルケア紀後期に存在し,活発に活動していた.
- これらの微生物のプロセスは,地球の大気中の酸素の有意な上昇を先行した可能性が高い.
- この発見は,地球規模の生地化学サイクルに微生物が早期に影響を及ぼした証拠を示しています.
さらに関連する動画
関連する概念動画
Diversity of Archaea II
Archaea, one of the three domains of life, exhibit remarkable diversity and adaptability, thriving in both extreme and moderate environments. Historically, most identified archaea have been classified into two major phyla: Euryarchaeota and Crenarchaeota. However, recent molecular studies have expanded this classification to include three additional phyla: Thaumarchaeota, Nanoarchaeota, and Korarchaeota, each exhibiting unique characteristics and ecological roles.Thaumarchaeota: Mesophiles...
Origin of Photosynthesis
Photosynthesis represents a fundamental biological process that transformed Earth's atmosphere and paved the way for complex life. Emerging roughly 3.4–3.8 billion years ago, the earliest photosynthetic organisms harnessed light energy to produce organic compounds. These anoxygenic phototrophs used electron donors like hydrogen sulfide (H₂S) or ferrous iron (Fe²⁺), rather than water, and did not release molecular oxygen (O₂) as a byproduct. Various groups, including green sulfur and purple...
The Nitrogen Cycle
Nitrogen atoms, present in all proteins and DNA, are recycled between abiotic and biotic components of the ecosystem. However, the primary form of nitrogen on Earth is nitrogen gas, which cannot be used by most animals and plants. Thus, nitrogen gas must first be converted into a usable form by nitrogen-fixing bacteria before it can be cycled through other living organisms. The use of nitrogen-containing fertilizers and animal waste products in human agriculture has greatly influenced the...
Inorganic Nitrogen Assimilation
Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme nitrate reductase...
Origin of Cellular Life
The origin of life on Earth is a complex and enigmatic event rooted in ancient biochemical processes and geological conditions. Experimental evidence supports the hypothesis that life began with the spontaneous formation of organic molecules such as RNA nucleotides, amino acids, and lipids under early Earth conditions. Factors like volcanic activity, intense UV radiation, and a reducing atmosphere without free oxygen likely facilitated these reactions. Hydrothermal vents on the ocean floor are...
Microbes and the Nitrogen Cycle
The nitrogen cycle is a complex biogeochemical process critical to maintaining the balance of nitrogenous compounds in ecosystems. This cycle involves multiple microbial-mediated transformations through which nitrogen changes oxidation states, supporting essential ecological functions and contributing to plant and microbial growth.Nitrogen Fixation and AmmonificationNitrogen fixation initiates the cycle by converting inert atmospheric nitrogen (N₂) into bioavailable ammonia (NH₃), a process...


