要約のみTohoku University掛川武課

Tsukamoto Yuya

博士学位論文の要旨及び審査結果の要旨 (Summary of Thesis(DR))othe

Tsukamoto, Yuya

336936

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

Geochemical study of Mn and P in modern andArchean hydrothermal systems: its importanceto activities of primitive microorganisms著者 Tsukamoto Yuyanumber 88学位授与機関 Tohoku University学位授与番号 理博第3279号URL http://hdl.handle.net/10097/00128532（別紙様式５）                                       論 文 内 容 要 旨 (NO．1) 氏  名 塚本 雄也 提出年 令和 2 年 学位論文の 題   目 Geochemical study of Mn and P in modern and Archean hydrothermal systems: its importance to activities of primitive microorganisms (現世・太古代熱水系におけるマンガン・リンの地球化学的研究：原始的な微生物活動の重要性について)  論 文 目 次  1. Acknowledgements 2. Abstract 3. Preface 4. Chapter 1 Geochemical and mineralogical studies of ca.12 Ma hydrothermal manganese ores in the Hokuroku district in Japan 5. Chapter 2 Metagenomic and mineralogical studies of Mn-rich hot spring sediments: Implications for roles of Mn-oxidizing bacteria and characterizations of biological Mn oxides 6. Chapter 3 Phosphate flux from oceanic crusts through Archean submarine hydrothermal activities and its importance 7. New findings and summary   Abstract  Biological activities have greatly altered compositions of atmosphere, hydrosphere and lithosphere on the Earth since the rise of first life around 3.8 Ga. Early biological activities have been studied intensively using bio-essential elements, such as carbon, nitrogen, oxygen and sulfur which are majorly hosted in atmosphere or hydrosphere. However, biological activities are also essentially sustained by bio-essential elements whose major reservoir is lithosphere, such as metals in enzymes and P (phosphorus). For example, Mn (manganese) and P are essential for cyanobacteria’s activities, because “Mn cluster (Mn4CaO5)” is essentially used to split water into oxygen during photosystemⅡand P is composed of RNA and DNA. Consequently, their supply process from lithosphere, hydrosphere to biosphere have been likely to control biological activities through time. Yet, their transportations from lithosphere, hydrosphere to biosphere have not been certain through time. In modern ocean, continental weathering of P is known to be major process to transport from lithosphere to hydrosphere. In addition, the following process from hydrosphere to biosphere have been well understood. On the other hands, large uncertainties exist for Mn leaching from lithosphere, and its mobility in hydrosphere and then to biosphere. （別紙様式５）                                       The Archean surface environments were considered as different worlds compared to modern Earth. The generally reducing surface environments might have caused different geochemical cycle of Mn. Many researchers consider that deficiencies of continental crusts also had limited P availabilities in the Archean oceans, and thus, limited biological productivities. On the other hands, P and Mn leaching from lithosphere to hydrosphere through submarine hydrothermal activities are not studied. In chapter 1, geochemical and mineralogical studies were conducted on Mn ores, which were formed by 12 Ma submarine hydrothermal activities in felsic volcanisms in the Hokuroku district, Akita prefecture, Japan. The mobilization of Mn from submarine volcanic rocks during rock/water interaction and evolution of Mn species in hydrothermal fluids were understood. Non-biological and biological processes to precipitate Mn oxide and Mn carbonates were also evaluated. These results clarified Mn leaching from lithosphere, and its mobility from hydrosphere to biosphere in modern environments. In chapter 2, metagenomic, geochemical and mineralogical studies were conducted for chemical precipitates or microbial mats at modern Mn-rich samples at Hachikuro or Mizusawa hot springs in Akita prefecture, Japan. Evidence of oxidation of soluble Mn2+ by Mn-oxidizing bacteria was obtained. Further, enzyme and Mn-oxidizing genes associated with Mn oxidation were specified. A series of metagenomic analyses robustly proved biologically mediated process oxidized Mn. These biological activities were stimulated by elemental supplies such as copper and Mn, which are essential for biological Mn oxidation, from lithosphere through water/rock interactions by hot spring water. In chapter 3, Mn and P mobilizations from early Archean basaltic ocean floor were examined. Investigations on Archean basaltic ocean floor revealed that it could be an important P sources through submarine hydrothermal activities, and P flux from the basalt into ocean sustained contemporary biosphere. Mn was also confirmed to be significantly leached from the basalt. Combining these results revealed that supply process of Mn and P from lithosphere, hydrosphere to biosphere in modern and Archean environments. In particular, leaching elements from lithosphere has been likely to stimulate biological activities. Consequently, their elemental fluxes have played significant roles of biological evolution through time. 別 紙  論文審査の結果の要旨   塚本雄也は生物進化史におけるリンとマンガンの重要性に着目し研究を行なった。マンガンやリンは、もともと岩石圏に存在し、それが岩石・水反応で岩石から水圏に移動し、最終的に生物圏に取り込まれる。これら移動過程や、生物への取り込み過程、進化しの中での元素サイクルの様子は不明であった。塚本くんはこれらの問題にアプローチするために、以下の３つの課題を設定し、博士論文課題研究を行なった。 (1)秋田県北鹿地域中新世マンガン鉱床形成時の岩石・水・微生物反応に関する研究。 (2)遺伝子解析による秋田県八九郎温泉におけるマンガン酸化菌とマンガン酸化酵素の検出。 (3)太古代海底玄武岩からのリンとマンガンの溶脱と初期生命活動に対する制約。 (1)の課題において、秋田県北鹿地域の詳細な地質調査を行い、マンガン鉱床形成地質現場を３次元的に捉えることに成功した。さらにマンガン鉱石中に有機物―轟石―石英―方解石がサブミクロン単位で互層をなす構造を見出した。詳細な TEM, STEM,ラマン分光分析などで、これらは 1200 万年前の海底熱水活動で噴出したマンガンが、マンガン酸化菌によって鉱物化した痕跡であることを新たに見出された。現生海底のマンガンノジュール形成に微生物活動が関与していたかしばしば議論されるが、本研究によって微生物活動の重要性や証拠が新たに提示されたことになる。 (2) の課題においては、マンガン酸化物層からマンガン酸化菌特有の遺伝子を取り出すことに世界で初めて成功した。マンガン酸化物が微生物活動によって形成されたことを実証した初めての例である。さらにマンガン酸化酵素であるマルチカッパーオキシターゼを同一試料から検出した。天然におけるマンガン酸化現場での検出は世界で初めてである。 (3) の課題において、太古代海底玄武岩を海水や熱水との反応の違いによって分類し、詳細な鉱物学的研究を行なった。それによって主に初生リン酸塩鉱物の溶解と再沈殿、完全溶脱の様子が解明された。このことは、大陸がなくても海底からのリンの供給があり、それが初期生物生態系を支えていた可能性を示す画期的な結果を得ることができた。 自立して研究活動を行うに必要な高度の研究能力と学識を有することを示している。したがって，塚本雄也提出の博士論文は，博士（理学）の学位論文として合格と認める。  

Geochemical study of Mn and P in modern and Archean hydrothermal systems: its importance to activities of primitive microorganisms

Tohoku University博士（理学）博士学位論文 (Thesis(doctor))要約のみthesi

339992

Geochemical study of Mn and P in modern andArchean hydrothermal systems: its importanceto activities of primitive microorganisms著者 Tsukamoto Yuya学位授与機関 Tohoku University学位授与番号 11301甲第19033号URL http://hdl.handle.net/10097/00128467    博士論文   Geochemical study of Mn and P  in modern and Archean hydrothermal systems:  its importance to activities of primitive microorganisms   (現世・太古代熱水系におけるマンガン・リンの地球化学的研究： 原始的な微生物活動の重要性について)       Yuya Tsukamoto 塚本 雄也  令和元年 (Defended February, 2020)   Table of contents    1. Acknowledgements….…………….…..…………………….………………..3  2. Abstract……………………………………………………………………….5  3. Preface………………………………………..……………………………….7  4. Chapter 1 Geochemical and mineralogical studies of ca.12 Ma hydrothermal manganese ores in the Hokuroku district in Japan.……….13  5. Chapter 2 Metagenomic, geochemical, and mineralogical studies of Mn-rich hot spring sediments: Implications for roles of Mn-oxidizing bacteria and characterizations of biological Mn oxides……….………….………………75  6. Chapter 3 Phosphate flux from oceanic crusts through Archean submarine hydrothermal activities and its importance……..…………………..……..145  7. New findings and summary………….………..………………...…….….....194        Abstract  Biological activities have greatly altered compositions of atmosphere, hydrosphere, and lithosphere on the Earth since the rise of first life around 3.8 Ga. Early biological activities have been studied intensively using bio-essential elements, such as carbon, nitrogen, oxygen and sulfur, which are majorly present in atmosphere and hydrosphere. However, biological activities are also essentially sustained by bio-essential elements whose major reservoirs are lithosphere, such as metals in enzymes and P (phosphorus). Consequently, their supply process from lithosphere, hydrosphere to biosphere have likely controlled biological activities through time. For example, Mn (manganese) and P are essential for cyanobacteria’s activities, because “Mn cluster (Mn4CaO5)” is essentially used to split water into oxygen during photosystemⅡand P is an essential component of RNA and DNA. Yet, their transportations from lithosphere, hydrosphere to biosphere have not been certain in modern and Archean environments. In modern ocean, continental weathering is known to be major process to transport P from lithosphere to hydrosphere. In addition, the following process from hydrosphere to biosphere have been well understood. On the other hands, large uncertainties exist for Mn leaching from lithosphere, and its mobility in hydrosphere and then to biosphere. The Archean surface redox conditions were considered as different compared to those in modern Earth. The generally reducing surface environments might have caused different geochemical cycle of Mn. Many researchers consider that deficiencies of continental crusts also had limited P availabilities in the Archean oceans, and thus, limited biological productivities. On the other hands, P and Mn leaching from lithosphere to hydrosphere through submarine hydrothermal activities have not been studied. In chapter 1, geochemical and mineralogical studies were conducted on Mn ores, which were formed by 12 Ma submarine hydrothermal activities in felsic volcanisms in the Hokuroku district, Akita prefecture, Japan. The mobilization of Mn from submarine volcanic rocks during rock/water interaction and evolution of Mn species in hydrothermal fluids were understood. Non-biological and biological processes to precipitate Mn oxide and Mn carbonates were also evaluated. These results clarified Mn leaching from lithosphere, and its mobility from hydrosphere to biosphere in modern environments. In chapter 2, metagenomic, geochemical and mineralogical studies were conducted for chemical precipitates and microbial mats at modern Mn-rich samples at Hachikuro or Mizusawa hot springs in Akita prefecture, Japan. Evidence of oxidation of soluble Mn2+ by Mn-oxidizing bacteria was obtained. Further, enzyme and Mn-oxidizing genes associated with Mn oxidation were specified. A series of metagenomic analyses robustly proved biologically mediated process oxidized Mn. It is also demonstrated that supply of elements from lithosphere stimulate activities of Mn-oxidizing bacteria. In chapter 3, Mn and P mobilizations from early Archean oceanic basalts were examined. Investigations on Archean oceanic basalts revealed that it could be an important P sources through submarine hydrothermal activities, and P flux from the basalt into ocean sustained contemporary biosphere. Mn was also confirmed to be significantly leached from the basalt. Combining these results revealed that supply process of Mn and P from lithosphere, hydrosphere to biosphere in modern and Archean environments. In particular, leaching elements from lithosphere has likely stimulate biological activities. Consequently, their elemental fluxes have played significant roles of biological evolution through time. 

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現生・太古代熱水系におけるマンガン・リンの地球化学的研究：原始的な微生物活動の重要性について

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