微生物如何爬行（2/2）

Recently the New York Times reported the following:

How Microbes Got Their Crawl (2/2)

In the oceans and on land, scientists are discovering rare, transitional organisms that bridge the gap between Earth’s simplest cells and today’s complex ones.

The NYT - By Carl Zimmer - Carl Zimmer covers news about science for The Times and writes the Origins column.

ORIGINS

Feb. 18, 2026

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Even as scientists have improved at finding Asgard DNA, they are still struggling to study live Asgard cells. Christa Schleper, a microbiologist at the University of Vienna, and her colleagues spent eight years figuring out how to grow Asgards that they had found in oxygen-free sediment on the coast of Slovenia.

At last, the researchers put some live Asgards on glass slides and trained a video camera on them. When they sped up the footage, they saw the microbes crawling across the slide — the first time anyone had seen them in motion.

“There was a lot of shouting and jumping,” recalled Philipp Radler, a postdoctoral researcher in Dr. Schleper’s lab.

The movement of the Asgards offers some tantalizing clues to the origin of eukaryotes. They crawl by reshaping their cellular skeleton, building long tentacles that they use to reach out and grip the slide. Other prokaryotes don’t move this way — but eukaryotes do. The videos suggest that Asgards evolved some of the key hallmarks of eukaryotes, such as a skeleton they could use to crawl, long before eukaryotes existed.

Other scientists have also been investigating another crucial step in the origin of eukaryotes: how they gained mitochondria.

The ancestors of mitochondria must have been microbes that breathed oxygen, and so must have lived where oxygen was abundant. Asgards that lived in oxygen-free sediments would not have encountered them. But Dr. Baker’s new study offers some clues into how this monumental meet-up may have happened.

Dr. Baker and his colleagues have found many new Asgards thriving in coastal waters with high levels of oxygen. A close look at their genes revealed hints that they use the oxygen for their metabolism.

“They appear to breathe oxygen and eat organic carbon — which is very familiar to us because we’re doing that right now,” Dr. Baker said.

Dr. Archibald said that scientists had come up with a lot of different scenarios for how eukaryotes evolved, but that it was hard to evaluate them without solid data. The Asgards that Dr. Baker and other researchers are finding now bring the origin of eukaryotes into sharper focus.

“We’re really breaking down impasses with real organisms,” Dr. Archibald said.

Dr. Baker and his colleagues now argue that the first steps on the path to eukaryotes took place on early Earth, when it lacked oxygen. Early Asgard microbes evolved a cellular skeleton, using it to creep around the ocean floor.

Earth’s atmosphere started to change around 2.5 billion years ago. Certain bacteria evolved photosynthesis, enabling them to absorb carbon dioxide and sunlight to grow. They cast off oxygen as waste. That oxygen gradually built up in the atmosphere, and then penetrated shallow coastal waters.

For many microbes, the new oxygen was toxic. But some Asgard microbes that lived in coastal waters adapted to withstand oxygen, and then to thrive on it. “And then they passed that on to eukaryotes,” Dr. Baker speculated.

Dr. Baker also suspects that Asgard microbes encountered bacteria that would become mitochondria in oxygen-rich coastal waters. He points to his team’s survey of the sea off the coast of China, where they found bacteria closely related to mitochondria living in the same sediments as Asgard microbes.

Once Asgards gained mitochondria, they dramatically ramped up their oxygen-based metabolism. These new eukaryotes gained an abundant energy supply that allowed them to grow larger with more capabilities, like preying on prokaryotes. The world would never be the same.

Kathryn Appler, a microbial ecologist at the Pasteur Institute who worked on the new study with Dr. Baker, said that scientists do not have to travel back two billion years to test this hypothesis. Instead, they can search coastal waters today. It’s possible that living Asgards are following the same path that the first eukaryotes took, forming intimate partnerships with bacteria.

“It keeps me up at night sometimes, wondering what is happening in the sediments today,” Dr. Appler said.

Translation

微生物如何爬行（2/2）

在海洋和陸地上，科學家正在發現一些罕見的過渡生物，它們連接著地球上最簡單的細胞和如今複雜的細胞

2026年2月18日

（繼續）

儘管科學家在尋找阿斯嘉德DNA方面取得了進展，但他們仍在努力研究活的阿斯嘉德細胞。維也納大學的微生物學家Christa Schleper和她的同事們花了八年時間，才弄清楚如何培養他們在斯洛維尼亞海岸缺氧沉積物中發現的阿斯加德。

最終，研究人員將一些活的阿斯嘉德放在載玻片上，並用攝影機拍攝。當他們加快影片播放速度時，他們看到這些微生物在載玻片上爬行 - 這是人們第一次看到它們動作。

 Schleper博士的實驗室的博士後研究員回憶道: 「當時一片歡呼雀躍」。

阿斯嘉德的動作為真核生物的起源提供了一些令人著迷的線索。它們透過重塑細胞骨架來爬行，形成長長的觸手，用來伸出並抓住玻片。其他原核生物不會以這種方式移動 - 但真核生物會。這些影片表明，阿斯嘉德早在真核生物出現之前就進化出了真核生物的一些關鍵特徵，例如可以用來爬行的骨骼。

其他科學家也在研究真核生物起源的另一個關鍵步驟：它們是如何獲得粒線體(mitochondria) 的。

粒線體的祖先一定是呼吸氧氣的微生物，因此它們一定是生活在氧氣豐富的環境中。生活在無氧沉積物中的阿斯加德生物不會遇到它。但Baker博士的新研究為我們揭示了這場意義非凡的相遇是如何發生的。

Baker博士及其同事在富含氧氣的沿海水域中發現了許多新的「阿斯嘉德生物」。仔細分析它們的基因後發現，它們似乎利用氧氣進行新陳代謝。

Baker博士說: 「它們似乎呼吸氧氣，並進食有機碳 - 這對我們來說非常熟悉，因為我們現在就在這樣做」。

Archibald博士表示，科學家提出了許多關於真核生物如何演化的不同設想，但由於缺乏可靠的數據，很難對這些設想進行評估。Baker博士和其他研究人員現在發現的「阿斯嘉德生物」使真核生物的起源問題更加更加明確清晰。

Archibald博士說: 「我們正在用真實的生物體打破僵局」。

Baker博士及其同事現在認為，真核生物進化的第一步發生在早期地球上，當時地球上缺乏氧氣。早期的阿斯嘉微生物進化出了細胞骨架，並利用它在海底爬行。

大約25億年前，地球大氣層開始改變。某些細菌進化出了光合作用，使它們能夠吸收二氧化碳和陽光來生長。它們將氧氣作為廢物排出。這些氧氣逐漸在大氣中積累，然後滲透到淺海沿岸水域。

對許多微生物來說，這種新的氧氣是有毒的。但一些生活在沿海水域的阿斯嘉微生物適應了氧氣，最終在氧氣中繁衍生息。 Baker博士推測道: 「然後它們將這種能力傳給了真核生物」。

Baker博士也懷疑，阿斯嘉德微生物在富氧的沿岸水域中遇到了一些最終演化成粒線體的細菌。他指出，他的團隊對中國沿海海域進行了調查，在那裡，他們在與阿斯嘉德微生物相同的沉積物中發現了與粒線體密切相關的細菌。

阿斯嘉德微生物一旦擁有了粒線體，其以氧為基礎的代謝能力就顯著提升。這些新的真核生物獲得了豐富的能量來源，使其體型更大，能力更強，例如能夠捕食原核生物。世界從此發生了翻天覆地的變化。

巴斯德研究所的微生物生態學家Kathryn Appler與Baker博士共同參與了這項新研究。她表示，科學家們無需穿越回20億年前來驗證這項假設。他們只需在當今的沿海水域進行探索即可。或許，現在的阿斯嘉德微生物正沿著最先出現的真核生物所走過的路，與細菌建立起緊密的共生關係。

Appler博士說道: 「有時我會為此徹夜難眠，思考如今的沉積物中正在究竟發生了什麼」。

              So, new studies are shedding light on one of the biggest steps in the history of life: the evolution two billion years ago of complex cells from simpler ones. Earth’s atmosphere started to change around 2.5 billion years ago. Certain bacteria evolved photosynthesis, enabling them to absorb carbon dioxide and sunlight to grow. They cast off oxygen as waste. For many microbes, the new oxygen was toxic. But some Asgard microbes that lived in coastal waters adapted to withstand oxygen, and then to thrive on it. And then probably they passed that on to eukaryotes. Once Asgard gained mitochondria, they dramatically ramped up their oxygen-based metabolism. These new eukaryotes gained an abundant energy supply that allowed them to grow larger with more capabilities, such as preying on prokaryotes. Probably, this process is still taking place in our environment somewhere.

Note:

1. A mitochondrion (pl. mitochondria) (線粒體) is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy. They were discovered by Albert von Kölliker in 1857 in the voluntary muscles of insects. The term mitochondrion, meaning a thread-like granule, was coined by Carl Benda in 1898. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase popularized by Philip Siekevitz in a 1957 Scientific American article of the same name. (Wikipedia)