Researchers gain new insights into how the first cells on Earth were able to use hydrogen gas as an energy source

研究人員們獲得了，有關地球上首批細胞，如何能使用氫氣作為一種能源的新洞察力。

Hydrogen gas (H₂) is seen as a key to sustainable energy for the future. Yet it is an ancient form of energy. Even the very first cells on earth lived on H₂, which was produced in hydrothermal vents.

氫氣(H₂)被視為，未來可永續能源的一個關鍵。然而，它卻是一種古老的能量形式。即使是地球上最早的細胞也靠著，於熱液噴口產生的H₂生存。

Now a team of researchers led by William F. Martin from Heinrich Heine University Düsseldorf and Martina Preiner from the Max Planck Institute for Terrestrial Microbiology in Marburg, supported by researchers in Germany and Asia, has provided new insights into how the first cells on Earth came to harness H₂ as an energy source.

目前，一支由來自德國，杜塞爾多夫海因里希海涅大學的William F. Martin，及位於馬爾堡之馬克斯普朗克陸地微生物學研究所的Martina Preiner所領導，獲得德國及亞洲研究人員們支持的研究人員團隊已經提供了，有關地球上首批細胞，如何發生利用H₂，作為一種能源的新洞察力。

圖1. 於失落之城熱液田中的蘇利斯地層，這是一個產生氫氣的鹼性熱液噴口。

Sulis formation in the Lost City hydrothermal field, an alkaline hydrothermal vent that produces hydrogen.

Hydrogen gas is clean fuel. It burns with oxygen in the air to provide energy with no CO₂. Hydrogen is a key to sustainable energy for the future. Though humans are just now coming to realize the benefits of hydrogen gas (H₂ in chemical shorthand), Hydrogen is ancient energy. Microbes have known that H₂ is good fuel for as long as there has been life on Earth.

氫氣是潔淨的燃料。它與空氣中的氧燃燒，提供沒有CO₂的能量。氫是供未來可永續能源的一個關鍵。雖然，目前人類才開始意識到氫氣(化學簡寫為H₂)的益處。不過，氫是古老的能源。微生物已經知曉，只要地球上一直有生命，H₂就是好的燃料。

The very first cells on Earth lived from H₂ produced in hydrothermal vents, using the reaction of H₂ with CO₂ to make the molecules of life. Microbes that thrive from the reaction of H₂ and CO₂ can live in total darkness, inhabiting spooky, primordial habitats like deep-sea hydrothermal vents or hot rock formations deep within the Earth’s crust, environments where many scientists think that life itself arose.

於地球上最早的細胞，以熱液噴口產生的H₂生存，利用H₂與CO₂的反應，來產生生命的分子。由於H₂與CO₂的反應，而欣欣向榮的微生物，能生存於完全黑暗的環境中，棲息於詭異的原始棲息地。諸如深海的熱液噴口，或地殼內深處的熱岩層等，諸多科學家認為，是生命本身誕生處的環境。

Surprising new insights about how the first cells on Earth came to harness H₂ as an energy source are now reported in a new study from the team of William F. Martin at the University of Düsseldorf and Martina Preiner at the Max Planck Institute for Terrestrial Microbiology in Marburg with support from collaborators in Germany and Asia.

目前，於來自杜塞爾多夫海因里希海涅大學William F. Martin，及位於馬爾堡馬之克斯普朗克陸地微生物學研究所Martina Preiner，擁有來自德國及亞洲共同研究者們支持之團隊的一項新研究中，記述了有關地球上首批細胞，如何發生利用H₂作為一種能源，令人驚訝的新洞察力。

In order to harvest energy, cells first have to push the electrons from H₂ energetically uphill. “That is like asking a river to flow uphill instead of downhill, so cells need engineered solutions,” explains one of the three first authors of the study, Max Brabender.

為了獲取能量，首先細胞必須，將H₂中的電子強力向上推。該項研究的三位首要撰文人之一，Max Brabender解釋：「那像是，要求河流向上流動，而不是向下流動。因此，細胞需要經工程改造的解決方法。」

How cells solve that problem was discovered only 15 years ago by Wolfgang Buckel together with his colleague and Max Planck Institute’s founding Director Rolf Thauer in Marburg. They found that cells send the two electrons in hydrogen down different paths.

細胞如何解決那問題，僅15年前才由，Wolfgang Buckel與其同事，及位於馬爾堡之馬克斯普朗克研究所的創始所長Rolf Thauer，一起發現。他們發現了，細胞沿著不同路徑，發送氫中的兩個電子。

One electron goes far downhill, so far downhill that it sets something like a pulley (or a siphon) in motion that can pull the other electron energetically uphill. This process is called electron bifurcation. In cells, it requires several enzymes that send the electrons uphill to an ancient and essential biological electron carrier called ferredoxin.

一個電子向下遠去，向下這麼遠，以至於它使像是，在能將另一個電子強力拉上的移動中，滑輪(或虹吸管)之類的東西。此過程被稱為電子分岔。在細胞中，這需要幾種酵素，來將電子向上發送到，一種古老且不可或缺，被稱為鐵氧化還原蛋白的生物電子載體中。

The new study shows that at pH 8.5, typical of naturally alkaline vents, “no proteins are required,” explains Wolfgang Buckel, co-author on the study, “the H–H bond of H2 splits on the iron surface, generating protons that are consumed by the alkaline water and electrons that are then easily transferred directly to ferredoxin.”

這項新研究顯示，在典型的天然鹼性噴口，pH值8.5下，該項研究合撰人，Wolfgang Buckel解釋：「無需蛋白質。H₂的H-H鍵，在鐵表面上分裂，產生被鹼性水及之後，容易直接被轉移到鐵氧化還原蛋白上之電子消耗的質子。」

How an energetically uphill reaction could have worked in early evolution, before there were enzymes or cells, has been a very tough puzzle. “Several different theories have proposed how the environment might have pushed electrons energetically uphill to ferredoxin before the origin of electron bifurcation,“ says Martin, “we have identified a process that could not be simpler and that works in the natural conditions of hydrothermal vents”.

在有酵素或細胞之前，一種強力向上的反應，於早期演化中，如何可能曾起作用，一直是個非常棘手的謎題。Martin宣稱：「若干種不同理論曾經提出，在電子分叉起源之前，環境如何可能曾強力將電子，向上推到鐵氧化還原蛋白上。我們已經確認一種，不可能更簡單且在熱液噴口之自然條件下，起作用的變化過程。」

Since the discovery of electron bifurcation, scientists have found that the process is both ancient and absolutely essential in microbes that live from H₂. The vexing problem for evolutionarily-minded chemists like Martina Preiner, whose team in Marburg focusses on the impact of the environment on reactions that microbes use today and possibly used at life’s origin, is:

打從發現電子分叉以來，科學家們已經發現，此變化過程既古老，且在以H₂生存的微生物中，是絕對不可或缺的。就像Martina Preiner(其在馬爾堡的團隊，著重於環境對當今微生物所使用，且可能被使用於生命起源時之反應的影響)具有演化思想的化學家而言，令人煩惱的問題是：

How was H₂ harnessed for CO₂ fixing pathways before there were complicated proteins? “Metals provide answers,”, she says, “at the onset of life, metals under ancient environmental conditions can make the electrons from H₂ accessible. We can see relicts of that primordial chemistry preserved in the biology of modern cells. ”

在有複雜的蛋白質之前，H₂如何被利用供作CO₂固定途徑？她宣稱：「金屬提供了答案。在生命開始時，於遠古環境條件下，金屬能使來自H₂的電子容易進入。我們能看到，於現代細胞生物中，保存的原始化學遺跡。」

But metals alone are not enough. “H₂ needs to be produced by the environment as well” adds co-first author Delfina Pereira from Preiner’s lab. Such environments are found in hydrothermal vents, where water interacts with iron-containing rocks to make H₂ and where microbes still live today from that hydrogen as their source of energy.

不過，僅金屬不夠。來自Preiner實驗室的共同首要撰文人，Delfina Pereira附言：「H₂ 也需由環境產生。」此類環境，於熱液噴口中被發現。在此水與含鐵岩石交互作用，產生H₂。且當今在此的微生物仍然以那種氫，作為生存的能量來源。

Hydrothermal vents, both modern and ancient, generate H₂ in such large amounts that the gas can turn iron-containing minerals into shiny metallic iron. “That hydrogen can make metallic iron out of minerals is no secret” says Harun Tüysüz, expert for high-tech materials at the Max-Planck-Institut für Kohlenforschung in Mülheim and coauthor on the study. “Many processes in chemical industry use H₂ to make metals out of minerals during the reaction.”

現代及古代的熱液噴口，產生如此大量的H₂，以至於該種氣體能將含鐵礦物，轉變成閃亮的金屬鐵。該項研究合撰人，位於米爾海姆之馬克斯普朗克媒碳研究所的高科技材料專家，Harun Tüysüz宣稱：「那種氫能從礦物，獲得金屬鐵，不是秘密。在化學工業中許多工序，於反應過程中，使用H₂來從礦物獲得金屬。」

The surprise is that nature does this too, especially at hydrothermal vents, and that this naturally deposited iron could have played a crucial role at the origin of life.

Iron was the only metal identified in the new study that was able to send the electrons in H₂ uphill to ferredoxin.

令人驚訝的事是，大自然也進行此事，特別是在熱液噴口。而且這種自然沉積的鐵可能，曾在生命的起源中，扮演一種至關重要的角色。在該項新研究中，鐵是唯一被確認，能將H₂中的電子，傳送到鐵氧化還原蛋白的金屬。

But the reaction only works under alkaline conditions like those in a certain type of hydrothermal vents. Natalia Mrnjavac from the Düsseldorf group and co-first author on the study points out:

不過，此反應僅在，如那些於某種類型熱液噴口中的鹼性條件下，起作用。該項研究首要共同撰文人，來自杜塞爾多夫海因里希海涅大學的Natalia Mrnjavac指出：

“This fits well with the theory that life arose in such environments. The most exciting thing is that such simple chemical reactions can close an important gap in understanding the complex process of origins, and that we can see those reactions working under the conditions of ancient hydrothermal vents in the laboratory today.”

「這與生命起源於，這樣環境中的理論非常吻合。最令人振奮的事是，如此簡單的化學反應能縮小，於瞭解起源之複雜過程中，一項重要的空白處。而且，目前於實驗室中，我們能在古代熱液噴口的條件下，看到那些反應。」

網址：https://www.mpg.de/21725781/0320-terr-harnessing-hydrogen-at-life-s-origin-153410-x?c=2249

翻譯：許東榮