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One fifth of all mammal species today are bats. And that's awesome, because they help us out in all sorts of ways.
如今在所有哺乳动物种类中，有五分之一是蝙蝠。这很棒，因为它们以各种方式帮助我们。
Like, they pollinate a lot of plants, help regrow forests and control pests, and their poop is pretty excellent fertilizer. Plus, they're just really cool.
比如，它们给很多植物授粉，帮助森林再生，控制害虫，它们的粪便是很好的肥料。另外，它们真的很酷。
Some of them can sense magnetic fields, or use sound to find their food—and, of course, there's the one thing they all have in common: they can truly fly.
一些蝙蝠可以感应磁场或是利用声音定位它们的食物——当然，它们都有一点共性：它们是真的会飞。
They're the only mammals around capable of powered flight without the help of machines.
它们是唯一之中不借助机械力量就能动力飞行的哺乳动物。
But they're also somewhat notorious for something else: being flying sacks of germs.
但它们也因为某些原因而臭名昭著：它们是飞行的病菌袋。
You might have noticed that part, what with all the talk about zoonotic diseases that's been happening lately.
你可能已经注意到了关于最近发生的人畜共患病的讨论。
Those are diseases that are passed to humans from other animals. And while bats aren't to blame for everything,
那些疾病通过其他动物传染给人类。虽然这一切不能都怪蝙蝠，
they have played a role in the transmission of at least 11 viruses —probably 12, counting SARS-CoV-2.
但它们在至少11种病毒的传播中发挥了作用——算上SARS-CoV-2的话，就是12种。
These diseases aren't the bats' fault, of course. If anything, they're ours.
当然这些疾病并不都是蝙蝠的错。如果有错，也是人类的错。
Research shows that disturbing animal habitats is usually what causes the transfer of a zoonotic disease to humans.
研究表明，干扰动物栖息地通常是导致人畜共患病传染给人类的原因。
Still, bats in particular do carry a lot of viruses. And that's because they have unique immune systems.
但蝙蝠携带的病毒尤其的多。这是因为它们拥有独特的免疫系统。
Which means we can learn a lot about these pathogens and their effects by studying bats.
这意味着我们可以通过研究蝙蝠来更多地了解这些病原体以及它们的影响。
In fact, bat immune systems are so special that what we learn from them could someday help us treat a wide variety of conditions, from cancer to diabetes.
实际上，蝙蝠的免疫系统非常特别，我们从中所了解到的知识或许可以在未来可以帮助我们治愈各种疾病，如癌症和糖尿病。
And the kicker is: bats probably have weird immune systems because they fly! Unlike gliding, flapping flight requires a huge amount of energy.
问题是：蝙蝠有奇怪的免疫系统可能是因为它们会飞！和滑行不同，扑翼飞行需要大量的能量。
So, bats have evolved ways to kick their cellular fuel production into high gear—mainly, by putting their mitochondria into overdrive.
所以，蝙蝠已经进化出一种方法来提高细胞的燃料生产效率——主要是通过让它们的线粒体超负荷运转。
Those are special compartments within cells that turn food into fuel. But there's a catch!
那些都是位于细胞内部的特别区室，这些细胞可以将食物转化成燃料。但这是一个陷阱！
When mitochondria convert nutrients into energy, they also create byproducts called reactive oxygen species.
当线粒体将营养转换成能量时，它们还会创造出一种被称为活性氧的副产品。
So basically, mitochondrial exhaust fumes, in the form of really reactive molecules which contain oxygen. Now, these aren't all bad.
所以基本上，线粒体废气，以含有氧气的活性分子的形式存在。这些都不是坏事。
The immune system uses them to rouse immune cells to action and kill bacterial invaders. But, they can also cause a lot of damage.
免疫系统利用它们唤醒免疫细胞行动起来，杀死入侵的细菌。但是它们也会造成大量伤害。
They can weaken cell membranes, mess with proteins, and even break DNA, and because of that, they play an important role in diseases like cancer and arthritis.
它们会破坏细胞膜，扰乱蛋白质，甚至破坏DNA，因此，它们在癌症和关节炎等疾病中起到关键作用。
Cells can try to keep them in check with antioxidants — compounds that essentially neutralize these overeager molecules.
细胞可以尝试用抗氧化剂来控制它们——这种化合物基本上可以中和这些过度活跃的分子。
But those can only do so much, and when the balance gets out of whack, cells experience a condition called oxidative stress.
但它们能做的也只有这些，但平衡失衡时，细胞就会经历一种叫做氧化应激的状态。
This is when most of the DNA damage happens.
大多数DNA损伤就发生在此时。
So, bats' supercharged mitochondria mean extremely high levels of oxidative stress—which, in turn, means constantly high levels of DNA damage.
所以蝙蝠的超动力线粒体意味着极高水平的氧化应激——这反过来意味着持续高水平的DNA损伤。
But since bats don't immediately get super-cancer after their maiden flight,
但是因为蝙蝠不会在首次飞行后立刻患上超级癌症，
researchers have long suspected they've evolved ways to protect themselves from all this flight-related damage.
研究人员一直怀疑它们已经进化出了保护自己免受飞行相关伤害的方法。
And a few years ago, genetics studies found mutations which boost their ability to detect and repair damaged DNA.
几年前，基因研究发现突变增强了它们检测和修复受损DNA的能力。
Essentially, they've also turbocharged the mechanisms that prevent genetically damaged cells from replicating.
从本质上讲，它们还增强了阻止基因受损细胞复制的机制。
Which may also explain why they don't seem to get cancers very often.
这或许也能够解释为什么它们似乎不经常得癌症。
So, bats produce tons of energy without damaging their cells. Sounds pretty awesome, really. There's just one small problem.
所以蝙蝠能在不伤害细胞的同时生产大量能量。听起来还挺棒的，只是有一个小问题。
DNA damage can also be a sign of a viral infection, because viruses need to hijack the cell's genetic machinery to reproduce,
DNA损伤也可以是一种病毒性感染的迹象，因为病毒需要劫持细胞的遗传机制来繁殖，
and that process usually involves some strategic snipping. So, naturally, DNA damage triggers an immune response: inflammation.
并且这一过程通常涉及一些战略性削减。因此，DNA损伤自然会引发免疫反应：炎症。
Essentially, when cells detect DNA damage or other signs of infection, they chemically call in white blood cells.
从本质上讲，当细胞检测大DNA损伤或其他感染迹象时，它们会用化学的方法召集白细胞。
These cells kill and destroy pathogens using a variety of genetic and chemical tools.
这些细胞会利用各种基因和化学工具杀死并摧毁病原体。
And they also help control how the inflammation unfolds—like, by bringing in additional white blood cells
它们还有助于控制炎症的展开方式，比如带来更多的白血球，
or switching some of them from germ-killing to tissue repair once the invasion is over.
或者在入侵结束后将一些白血球从杀灭细菌转为修复组织。
This immediate or acute inflammatory response helps to get rid of the invaders and promotes healing.
这种即刻的或急性的炎症反应帮助于清除入侵者，促进愈合。
But remember, thanks to their supercharged mitochondria, bat cells experience constant DNA damage.
但要记住，由于它们的超动力线粒体，蝙蝠细胞会经历持续的DNA损伤。
They can repair this damage thanks to those advanced DNA-repair tools.
由于这些先进的DNA修复工具，它们可以修复这些损伤。
But the damaged DNA should still light an immune flare before it's fixed.
但是在修复之前，受损的DNA仍然会触发免疫系统。
So bats would experience super-inflammation all the time! And prolonged, chronic, and systemic inflammation isn't so great.
所以蝙蝠会一直经历超级炎症！并且长期的、慢性的、全身性的炎症就不那么好了。
White blood cells and the processes they set in motion can be really destructive to the body's own tissues.
白细胞及其启动的过程可能会对人体自身组织造成破坏。
In short, too much inflammation can lead to organ failure and even death. So flight should be a death sentence.
总之，过多的炎症可以导致器官衰竭甚至死亡。所以逃走就是等死。
Except, bats have evolved some neat ways to knock down inflammation, too. For one thing, they dampen the activity of STING proteins.
除了，蝙蝠还进化出了一些简单的方法来消除炎症。首先，它们抑制了STING蛋白的活性。
These proteins are one of the ways mammalian cells trigger an inflammatory response when a virus is detected.
当检测到病毒时，这些蛋白质是哺乳动物细胞触发炎症反应的方式之一。
Also, a genetic analysis of multiple bat genomes showed that they're the only mammals that completely lack genes for PYHIN proteins—
同样，对多种蝙蝠基因组的基因分析表明它们是唯一一种完全缺乏PYHIN蛋白基因的哺乳动物——
another set of inflammation-triggering sensors activated by damaged DNA. And those are just part of the story.
这是另一组由受损DNA激活的炎症触发传感器。这些只是故事的一部分。
It will still be a while before we completely understand how bats prevent or dampen inflammation in their bodies,
我们还需要一段时间才能完全了解蝙蝠如何预防或抑制体内的炎症，
because it seems like every time they look, researchers keep finding more of these adaptations.
因为似乎每次研究人员研究的时候，他们都在不断地发现更多的这种适应性。
So to recap: we know that to make sustained flight possible, bats have ramped up fuel production
总结一下：我们知道，为了使持续飞行成为可能，蝙蝠已经提高了燃料产量
and DNA damage detection while dialing inflammation down to a 1.
和DNA损伤检测，同时把炎症降低到1。
But we know that inflammation is one of the big ways the immune system fends off intruders.
但是我们知道，炎症是免疫系统抵御入侵者的主要方式之一。
So, doesn't that leave them open to all kinds of actual pathogens?! And... The answer is yes!
所以这难道不会让它们接触到各种真正的病原体吗？！答案是肯定的！
Around the turn of the 21st century, scientists discovered that bats act as a reservoir for a lot of viruses that are extremely dangerous to humans.
在21世纪之交，科学家们发现蝙蝠是许多对人类极其危险的病毒的蓄水池。
This includes filoviruses, which cause hemorrhagic fevers, like Marburg or Ebola.
其中包括会引起出血热，如马尔堡或埃博拉等的线状病毒。
Also, henipaviruses like Hendra and Nipah, both of which can cause fatal brain infections and, of course, coronaviruses, like SARS, MERS,
同样，像亨德拉病毒和尼帕病毒这样的亨尼病毒属，它们会导致致命脑感染，当然还有冠状病毒，如非典、中东呼吸综合征
and (most likely) the notorious new coronavirus that started the COVID-19 epidemic.
（很有可能）还包括现在引发了COVID-19大流行的臭名昭著的新型冠状病毒。
And there's mounting evidence that bats were involved in transmitting these diseases to humans, either directly or indirectly, like by infecting farm animals.
有越来越多的证据表明，蝙蝠直接或间接地将这些疾病传播给人类，比如感染农场动物。
Bats are also suspected of having given us other diseases in the past, like mumps, measles, and hepatitis B! But here comes another magic thing about bats:
蝙蝠还被怀疑在过去给我们带来了其他疾病，如腮腺炎、麻疹和乙型肝炎！但蝙蝠还有另一个神奇之处：
