What Physical ‘Life Force’ Turns Biology’s Wheels?

Kristina Armitage/ Quanta Magazine

克里斯蒂娜·阿米蒂奇/广达杂志

Y ou’re the earliest known life form.

你是已知最早的生命形式。

There’s no food around right now.

现在周围没有食物。

It would be great to go somewhere else.

如果能去别的地方就好了。

But you’re stuck.

但你被困住了。

Really stuck.

真的卡住了。

At your size (a couple of microns), water feels like tar, or rather, it feels the way being stuck in tar will eventually feel to a human.

在你的尺寸（几微米）下，水感觉就像焦油，或者更确切地说，它的感觉就像人类最终被困在焦油中的感觉一样。

What do you do?

你做什么工作？

[One or more billion years later.] You’ve found the perfect solution.

[十亿年或十亿年以后。]你已经找到了完美的解决方案。

“You can assume the system is working optimally,” said Aravinthan Samuel , a biophysicist at Harvard University.

哈佛大学生物物理学家阿拉文森·塞缪尔 (Aravinthan Samuel) 表示：“你可以假设该系统正在以最佳状态运行。”

Evolution has created the flagellar motor, a combination propeller/brain that enables single-celled bacteria to move toward food sources.

进化创造了鞭毛马达，这是一种螺旋桨/大脑的组合，使单细胞细菌能够向食物源移动。

It’s an electric motor that rotates at several hundred revolutions per second — faster than the flywheel in a race car engine — to twirl a tail-like flagellum that pushes the cell along.

它是一种每秒旋转数百转的电动机——比赛车发动机中的飞轮还快——旋转尾巴状的鞭毛，推动细胞前进。

When the flagellar motor rotates counterclockwise, it propels the cell through the water 10 or more times its own length in a second.

当鞭毛马达逆时针旋转时，它在一秒钟内推动细胞在水中移动其自身长度的 10 倍或更多倍。

The motor can also rotate clockwise, causing the cell to tumble about randomly.

电机也可以顺时针旋转，导致电池随机翻滚。

This amazing, self-assembling, signal-processing, direction-switching molecular machine is so powerful yet so spare that, billions of years later, it’s still used by bacteria in virtually every gut and puddle on Earth.

这种令人惊奇的、自组装、信号处理、方向转换的分子机器是如此强大，但又如此备用，以至于数十亿年后，它仍然被地球上几乎每个肠道和水坑中的细菌所使用。

I n philosophy, “qualia” refers to the subjective qualities of our experience: what it’s like for Alice to see blue or for Bob to feel delighted.

在哲学中，“感受性”指的是我们体验的主观品质：爱丽丝看到蓝色或鲍勃感到高兴是什么感觉。

Qualia are “the ways things seem to us,” as the late philosopher Daniel Dennett put it.

正如已故哲学家丹尼尔·丹尼特所说，感受性是“事物在我们看来的方式”。

In these essays, our columnists follow their curiosity, and explore important but not necessarily answerable scientific questions.

在这些文章中，我们的专栏作家追随他们的好奇心，探索重要但不一定可以回答的科学问题。

Since the discovery of the bacterial flagellar motor in the 1970s, biologists and creationists alike have marveled at its design like medieval architects staring with awe at the dome of the Pantheon built by their Roman ancestors.

自从 20 世纪 70 年代发现细菌鞭毛马达以来，生物学家和神创论者都对其设计惊叹不已，就像中世纪建筑师敬畏地凝视着罗马祖先建造的万神殿的圆顶一样。

It’s hard to fathom the level of engineering achievable by a billion years of bacterial evolution, especially with only 20 minutes between cell generations, which allows for a truly astronomical number of mutations and trial runs.

很难想象细菌十亿年的进化所能达到的工程水平，尤其是细胞世代之间只有 20 分钟的时间，这允许真正天文数字的突变和试运行。

Creationists hold up the bacterial flagellar motor as a prime example of intelligent design — specifically the concept of “irreducible complexity,” a biological system so intricate, they say, that it couldn’t possibly have arisen in stages through the gradual, stepwise process of Darwinian evolution.

神创论者将细菌鞭毛马达视为智能设计的一个典型例子——特别是“不可简化的复杂性”的概念，他们说，这是一个如此复杂的生物系统，不可能通过达尔文进化论的渐进、逐步过程分阶段出现。

Over the past few decades, scientists have toiled to unravel how the flagellar motor works — namely, how it rotates and switches directions.

在过去的几十年里，科学家们一直致力于解开鞭毛马达的工作原理，即它如何旋转和改变方向。

Now they finally have.

现在他们终于有了。

A wave of studies since 2020 has cracked the molecular structures of the flagellar motor’s parts, including, most importantly, the small cogwheels that turn the larger cogwheel at the flagellum’s base.

自 2020 年以来的一波研究已经破解了鞭毛马达部件的分子结构，其中最重要的是，驱动鞭毛基部较大齿轮的小齿轮。

The final pieces of this dynamic puzzle fell into place as recently as March 2026.

这个动态拼图的最后一块拼图直到 2026 年 3 月才已就位。

It’s hard to fathom the level of engineering achievable by a billion years of bacterial evolution.

很难想象十亿年的细菌进化所能达到的工程水平。

“My lifelong quest is now fulfilled,” said Mike Manson , a professor emeritus of biophysics at Texas A&M University who started studying the flagellar motor in the 1970s.

“我一生的追求现在已经实现了，”德克萨斯 A&M 大学生物物理学名誉教授迈克·曼森 (Mike Manson) 说，他从 20 世纪 70 年代开始研究鞭毛马达。

“I finally understand how this thing I’ve been studying for 50 years actually works.

“我终于明白了我研究了 50 年的这个东西到底是如何运作的。

That’s about as satisfying as can be.”

这已经是最令人满意的了。”

The workings of the flagellar motor are ingenious indeed.

鞭毛马达的工作原理确实很巧妙。

But when I began interviewing these scientists about what they’ve figured out, I didn’t anticipate that the explanation of the motor would clarify all of biology for someone like me, who seeks mechanistic, physical explanations.

但当我开始采访这些科学家了解他们的发现时，我并没有预料到对电机的解释能为像我这样寻求机械、物理解释的人澄清所有生物学问题。

The machine, I learned, exploits a driving force I had not known about (though biophysicists have) — the physical “life force” that powers processes in cells.

我了解到，这台机器利用了一种我不知道的驱动力（尽管生物物理学家知道）——为细胞中的过程提供动力的物理“生命力”。

This “proton motive force” doesn’t just turn the cogs of the flagellar motor; it’s the juice we all run on.

这种“质子动力”不仅转动鞭毛马达的齿轮，而且还转动鞭毛马达的齿轮。这是我们赖以生存的果汁。

The flagellar motor was discovered by the late Howard Berg, an ingenious experimenter who spent most of his career at Harvard.

鞭毛马达是由已故的霍华德·伯格发现的，他是一位聪明的实验家，他的大部分职业生涯都在哈佛大学度过。

Berg set out in the early 1970s to apply his training in physics to understanding how bacteria move.

Berg 于 20 世纪 70 年代初开始运用他在物理学方面的训练来了解细菌如何移动。

The problem was that, under a microscope, Escherichia coli , Salmonella , and other motile bacteria almost instantly swam out of frame.

问题是，在显微镜下，大肠杆菌、沙门氏菌和其他运动细菌几乎立即游出镜框。

So Berg invented and built an automatic tracking microscope that could keep a bacterium in view as it moved around.

因此，伯格发明并制造了一种自动跟踪显微镜，可以在细菌移动时对其进行观察。

“What it recorded were all the corrections that had to be made to the microscope stage in order to keep the bacterium in place, and that of course gives you a readout of what the path of the swimming bacterium was,” said Manson, who joined Berg’s project as a postdoc in 1975.

曼森于 1975 年以博士后身份加入伯格的项目，他说：“它记录的是为了使细菌保持在适当的位置而必须对显微镜载物台进行的所有修正，这当然可以让你读出游动细菌的路径。”

The data revealed that bacteria “run and tumble” — that is, they switch back and forth between swimming straight and rolling around chaotically.

数据显示，细菌会“奔跑和翻滚”——也就是说，它们会在直线游动和混乱滚动之间来回切换。

Berg theorized that bacteria change their swimming state based on the chemical gradients sensed as they swim.

伯格的理论是，细菌根据游泳时感知到的化学梯度来改变其游泳状态。

Their default behavior is to swim straight.

它们的默认行为是笔直游动。

If the concentration of sugars and other nutrients is increasing, the cell keeps going forward.

如果糖和其他营养物质的浓度增加，细胞就会继续前进。

If the concentration drops, it tumbles; reoriented in a new direction, the bacterium then resumes swimming straight.

如果浓度下降，它就会翻滚；重新定向到新的方向后，细菌就会恢复直线游动。

This process keeps the bacterium in the vicinity of harvestable molecules, which it absorbs through channels in its cell wall and membrane.

这个过程使细菌保持在可收获分子附近，并通过细胞壁和细胞膜上的通道吸收这些分子。

A transmission electron microscopy image reveals the cluster of flagella that a Pseudomonas fluorescens bacteria uses to move around water in soil.

透射电子显微镜图像显示荧光假单胞菌细菌用来在土壤中的水周围移动的鞭毛簇。

Dr Tony Brain/Science Photo Library

托尼·布莱恩博士/科学图片库

Berg guessed that the flagellar motor was a rotor that turned the flagellum like a screw.

伯格猜测鞭毛马达是一个像螺丝一样转动鞭毛的转子。

“He did it by sticking two cells together by their flagella and seeing them spinning in opposite directions from each other,” Manson said.

曼森说：“他通过将两个细胞的鞭毛粘在一起并观察它们以相反的方向旋转来做到这一点。”

“From that, with no knowledge, he hypothesized that the bacterial flagellum rotates.

“据此，他在不知情的情况下推测细菌鞭毛会旋转。

Way ahead of his time.

远远领先于他的时代。

That was 50 years before understanding how this motor works.”

那是 50 年前我们才了解这种电机的工作原理。”

Further experiments indicated that the flagellar motor also switches direction.

进一步的实验表明鞭毛马达也会改变方向。

When its flagella — bacteria typically have several protruding from their surfaces — are all spinning counterclockwise, they form a bundle that trails behind the swimming cell like a braid in the wind, steering it straight.

当它的鞭毛（细菌通常有几个从其表面突出）全部逆时针旋转时，它们会形成一束，像风中的辫子一样拖在游泳细胞后面，引导它笔直前进。

But as soon as one flagellar motor reverses direction and starts rotating clockwise, the bundle falls apart; the reverse-twirling filament unravels the braid and puts the cell’s flagellar motors at cross-purposes, kicking the cell around.

但一旦一个鞭毛马达反转方向并开始顺时针旋转，鞭毛束就会散开；反向旋转的细丝会解开辫子，并使细胞的鞭毛马达处于相反的目的，从而踢动细胞。

Before Berg’s work, “the idea of a molecular motor was bonkers — no way anything rotates,” said Samuel, Berg’s former student who now runs a Harvard lab of his own.

在伯格的工作之前，“分子马达的想法是疯狂的——任何东西都不可能旋转，”伯格以前的学生塞缪尔说，他现在经营着自己的哈佛实验室。

It could wiggle, sure, but rotate?

当然，它可以摆动，但是可以旋转吗？

“It requires a certain geometry that people didn’t think was accessible to biology.”

“它需要某种人们认为生物学无法理解的几何形状。”

Au contraire.

相反。

“Biology can build wheels,” Samuel said.

“生物学可以制造轮子，”塞缪尔说。

“Now we know.”

“现在我们知道了。”

Improvements over the last 15 years in an imaging technique called cryo-EM (cryogenic electron microscopy) have enabled researchers to see the flagellar motor’s component parts.

过去 15 年，冷冻电子显微镜（cryo-EM）成像技术的进步使研究人员能够看到鞭毛马达的组成部分。

That has clarified how it works.

这已经阐明了它是如何工作的。

At the base of the motor is the “C ring” (or “cytoplasmic ring”), a ring of 34 identical proteins floating in the cytoplasm within the cell membrane.

马达的底部是“C 环”（或“细胞质环”），这是一个由 34 个相同蛋白质组成的环，漂浮在细胞膜内的细胞质中。

Scientists in the 1980s and ’90s figured out that when the C ring rotates, the flagellum does too.

20 世纪 80 年代和 90 年代的科学家发现，当 C 环旋转时，鞭毛也会旋转。

But why and how it rotates wasn’t obvious.

但其旋转的原因和方式尚不清楚。

David S.

大卫·S。

Goodsell/PDB101.rcsb.ord/Modified by Quanta Magazine

Goodsell/PDB101.rcsb.ord/由 Quanta 杂志修改

The stars of the show, recent research showed, are the motor’s “stators,” smaller protein complexes that anchor themselves above and outside the C ring.

最近的研究表明，这场秀的明星是电机的“定子”，这是一种较小的蛋白质复合物，固定在 C 环的上方和外侧。

The number of stators varies by bacterial species ( E.

定子的数量因细菌种类而异（E.

coli has 10 or 12 available per flagellum), and how many lock into the C ring at a given time depends on the weight of the cell or the viscosity of the surrounding fluid.

大肠杆菌的每个鞭毛有 10 或 12 个可用的鞭毛，并且在给定时间有多少锁入 C 环取决于细胞的重量或周围液体的粘度。

Each stator consists of two central proteins that dangle from the cell wall and five proteins of a different kind that form a pentagonal ring around the pair.

每个定子由两个悬挂在细胞壁上的中心蛋白质和五个不同种类的蛋白质组成，这些蛋白质在这对蛋白质周围形成五边形环。

This pentagonal structure is the part that rubs up against the C ring.

这个五边形结构就是与C环摩擦的部分。

The 5:2 geometry of the stators was revealed in 2020 in a pair of cryo-EM studies , one by Susan Lea and a team at the University of Oxford, and one from a group led by Nicholas Taylor of the University of Copenhagen and Marc Erhardt of Humboldt University of Berlin.

定子的 5:2 几何形状在 2020 年的两项冷冻电镜研究中得到揭示，其中一项由 Susan Lea 和牛津大学的团队进行，另一项由哥本哈根大学的 Nicholas Taylor 和柏林洪堡大学的 Marc Erhardt 领导的小组进行。

The finding pointed to a hypothesis about how the whole motor works: The stators’ pentagonal rings rotate, which then turns the larger C ring, and with it the whole flagellum.

这一发现提出了关于整个电机如何工作的假设：定子的五边形环旋转，然后旋转较大的 C 环，以及整个鞭毛。

Each pentagonal ring turns like a turnstile, one-tenth of a revolution at a time.

每个五边形环都像十字转门一样旋转，每次旋转十分之一圈。

What pushes through the turnstile is a stream of protons — the same positively charged particles found in atoms.

穿过十字转门的是质子流——与原子中发现的带正电粒子相同。

Protons flow into cells of their own accord, for reasons I’ll get to.

质子会自行流入细胞，原因我稍后会讲到。

This is the proton motive force.

这就是质子动力。

The asymmetric positioning of two proteins inside a pentagonal ring allows a proton from outside the cell to weakly bond to one of them.

五边形环内两种蛋白质的不对称定位允许来自细胞外的质子与其中之一弱结合。

As the proteins jostle, the proton unbinds, exerting torque on the ring as it goes.

当蛋白质相互碰撞时，质子就会解开，在环移动时对环施加扭矩。

That creates an opportunity for the same process to take place with the other central protein.

这为其他中心蛋白质发生相同的过程创造了机会。

In this way, protons effectively pedal the engine of the flagellar motor.

通过这种方式，质子有效地推动鞭毛马达的引擎。

Every second, more than 2,000 of them pass through the pentagonal turnstiles.

每秒都有超过2000人通过五角转门。

In December 2025, Samuel published the results of an experiment that verified this.

2025 年 12 月，Samuel 发表了验证这一点的实验结果。

Protons always want to flow into cells, never out.

质子总是想流入细胞，而不是流出。

In passing that way, they always push the pentagonal rings clockwise.

通过这种方式时，他们总是顺时针推动五边形环。

Normally, this turns the C ring counterclockwise (like the opposite turning of interlocking gears), which propels the swimming cell forward.

通常，这会使 C 环逆时针转动（就像互锁齿轮的相反转动一样），从而推动游泳细胞前进。

How, though, can the flagellar motor switch directions?

然而，鞭毛马达如何改变方向呢？

In 2024, another pair of cryo-EM studies , from Lea, then with a team at the National Institutes of Health, and a group led by Tina Iverson at Vanderbilt University, revealed the answer.

2024 年，Lea 与美国国立卫生研究院的一个团队以及范德比尔特大学蒂娜·艾弗森 (Tina Iverson) 领导的团队进行的另一项冷冻电镜研究揭示了答案。

Recall that a flagellar motor switches directions, causing the bacterium to tumble, when environmental conditions seem to be getting worse.

回想一下，当环境条件似乎变得更糟时，鞭毛马达会改变方向，导致细菌翻滚。

When fewer nutritious molecules drift in, the bacterium “phosphorylates” proteins called CheY, tagging them with phosphorus atoms.

当较少的营养分子漂入时，细菌会“磷酸化”名为 CheY 的蛋白质，并用磷原子标记它们。

Within milliseconds, phosphorylated CheY molecules diffuse around the cell, and one of them binds to one of the C-ring proteins.

在几毫秒内，磷酸化的 CheY 分子在细胞周围扩散，其中一个分子与 C 环蛋白之一结合。

This small change triggers a transformation: The protein flips into a different structural configuration, which flips the next protein, and then the next.

这个微小的变化引发了转变：蛋白质翻转成不同的结构配置，从而翻转下一个蛋白质，然后是下一个。

Almost instantly the whole C ring reshapes itself, like a hair clip snapping into the other of its two stable forms.

整个 C 环几乎立即重塑自身形状，就像一个发夹卡入其两个稳定形状中的另一个。

Samuel’s team confirmed that the system is sensitive to a single signaling molecule in a study published in March 2026.

Samuel 的团队在 2026 年 3 月发表的一项研究中证实，该系统对单个信号分子敏感。

While the C ring is in its altered shape, the stators — the little clockwise-revolving motors — rotate against the inner edge of the C ring, rather than its outer edge.

当 C 环的形状发生变化时，定子（顺时针旋转的小型电机）沿着 C 环的内边缘而不是外边缘旋转。

As a result, the C ring turns clockwise too.

结果，C环也顺时针转动。

The flagellar bundle falls apart, and the cell tumbles.

鞭毛束分崩离析，细胞翻滚。

Soon enough, the unstable phosphorus atom falls off the CheY protein, causing the proteins of the C ring to flip back to their original stable formation and turn counterclockwise again.

很快，不稳定的磷原子从 CheY 蛋白上脱落，导致 C 环蛋白翻转回原来的稳定结构，并再次逆时针旋转。

The bacterium returns to forward movement, in a new direction, is search of more food.

细菌又回到前进的方向，朝着一个新的方向，寻找更多的食物。

“It’s a really elegant way of turning a unidirectional power into bidirectional rotation of the large object,” said Lea, who is now at St. Jude Children’s Research Hospital.

“这是一种非常优雅的方式，可以将单向动力转化为大型物体的双向旋转，”现在在圣裘德儿童研究医院工作的 Lea 说。

The proton motive force that drives the flagellar motor was proposed in 1961 by Peter Mitchell, a biochemist who worked out of his own private lab at a country estate in Cornwall, England.

驱动鞭毛马达的质子动力是由生物化学家彼得·米切尔 (Peter Mitchell) 于 1961 年提出的，他在英国康沃尔郡一处乡村庄园的私人实验室中工作。

Though initially dismissed and even ridiculed, Mitchell went on to win the 1978 Nobel Prize in Chemistry for his idea that a current of protons constantly flows into the cell as the cell vigorously pumps them back out, and that this is the driving force behind key cellular processes.

尽管最初遭到驳斥甚至嘲笑，米切尔还是凭借他的观点获得了 1978 年诺贝尔化学奖，即质子流不断流入细胞，同时细胞将质子有力地泵出，这是关键细胞过程背后的驱动力。

Protons flow in because they’re diffusing from an area of high concentration (outside the cell) to an area of low concentration (inside).

质子流入是因为它们从高浓度区域（细胞外部）扩散到低浓度区域（细胞内部）。

There are fewer than 100 free protons inside a bacterium at a time, while a similar volume of the surrounding water has tens of thousands.

细菌内部的自由质子数量少于 100 个，而周围同等体积的水中则有数万个。

The cell maintains this state with machines called electron transport chains that pump out thousands of protons per second.

细胞通过称为电子传输链的机器来维持这种状态，该机器每秒泵出数千个质子。

As protons are pumped out, thousands more flow in, drawn by the net negative electric charge and the general tendency for entropy to rise as particles (in this case, protons) spread out in space ever more evenly.

当质子被抽出时，更多的质子被净负电荷和随着粒子（在本例中为质子）在空间中更加均匀地分布而熵增加的总体趋势吸引而流入。

Cells have rigged up all kinds of molecular machines that, like water mills on rivers, take advantage of proton currents coming into the cell.

细胞装配了各种分子机器，就像河流上的水磨机一样，利用进入细胞的质子流。

“It boggles the normal human understanding of how things work,” Manson said.

“这让人类对事物运作方式的正常理解感到困惑，”曼森说。

“How can you have thousands and thousands of protons coming into the cell every second and still have only a few dozen inside the cell?

“为什么每秒都有成千上万的质子进入细胞，而细胞内却只有几十个质子？

Because they bind to something, they get pumped out again.

因为它们与某物结合，所以它们会再次被抽出。

The equilibria are so incredibly fast.”

平衡速度快得令人难以置信。”

So what makes the cell go, what breathes life into the atomic arrangements, is the efficient removal of protons so that more protons will flow.

因此，使细胞运转、为原子排列注入生命的因素是有效去除质子，以便更多的质子流动。

“If you were to open up a channel to protons, they would come pouring into the cell, and the proton motive force would be gone instantly,” Manson said.

曼森说：“如果你打开质子的通道，它们就会涌入细胞，质子的动力就会立即消失。”

He’s seen this happen, when cells starve and can’t pump enough protons out.

当细胞挨饿并且无法泵出足够的质子时，他就亲眼目睹了这种情况的发生。

The voltage drops to nothing, and the cell’s machinery shuts down.

电压降至零，电池的机械装置关闭。

If you’re a bacterium, your flagellar motor stops.

如果你是细菌，你的鞭毛马达就会停止。

You’re stuck.

你被困住了。

Rarely have I loved biology more than when marveling at the flagellar motor and the influx of protons that turns its gears.

当我对鞭毛马达和驱动其齿轮的质子涌入感到惊叹时，我对生物学的热爱很少有过。

“The entropic energy of the proton motive force gets converted into the kinetic energy of the rotation,” Manson said.

“质子动力的熵能转化为旋转的动能，”曼森说。

“That’s all it is.

“仅此而已。

All of it is just that.

一切仅此而已。

If you understand that, you basically understand the underpinnings of all that happens in biology.”

如果你理解了这一点，你基本上就理解了生物学中发生的所有事情的基础。”

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《Quanta》杂志对评论进行审核，以促进知情、实质性、文明的对话。

Abusive, profane, self-promotional, misleading, incoherent or off-topic comments will be rejected.

辱骂、亵渎、自我推销、误导、语无伦次或偏离主题的评论将被拒绝。

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版主在正常工作时间（纽约时间）有工作人员，并且只能接受英文评论。