They've been here for billions of years,

它們已經存在數十億年了，

and what they are are single-celled microscopic organisms.

它們是單細胞微生物。

So they are one cell and they have this special property

它們只有一個細胞，而且還有個特徵

that they only have one piece of DNA.

就是只有一份 DNA。

They have very few genes,

擁有極少的基因

and genetic information to encode all of the traits that they carry out.

及遺傳資訊，來儲存所有它們表現的特徵。

And the way bacteria make a living

細菌賴以生存的方法是

is that they consume nutrients from the environment,

從環境中吸取養分，

they grow to twice their size, they cut themselves down in the middle,

成長兩倍後，從中分開，

and one cell becomes two, and so on and so on.

一分為二，二分為四，如此一直下去。

They just grow and divide, and grow and divide -- so a kind of boring life,

它們不停生長、分裂，然後再生長、分裂 — 有點無趣的生活，

except that what I would argue is that you have

但是我會說你與這些生物

an amazing interaction with these critters.

擁有驚人的互動關係。

I know you guys think of yourself as humans, and this is sort of how I think of you.

我知道你們自認是人類，而這大概是我如何看待你們的。

This man is supposed to represent

這個人是代表

a generic human being,

一般的人類，

and all of the circles in that man are all of the cells that make up your body.

那些人體內的圈圈，代表組成人體的細胞。

There is about a trillion human cells that make each one of us

每個人大約是由一兆個人體細胞所組成，

who we are and able to do all the things that we do,

讓我們能完成各式各樣的事

but you have 10 trillion bacterial cells

但是你一生中任何時刻

in you or on you at any moment in your life.

都有大約十兆個細菌細胞在你身上或體內。

So, 10 times more bacterial cells

所以，在一個人身上

than human cells on a human being.

有人體細胞數十倍的細菌細胞。

And of course it's the DNA that counts,

當然，DNA 組成比細胞數重要，

so here's all the A, T, Gs and Cs

所以這裡是組成你遺傳密碼的

that make up your genetic code, and give you all your charming characteristics.

所有 A, T, G, C，它們產生了你專屬的迷人特徵。

You have about 30,000 genes.

你有大約三萬個基因。

Well it turns out you have 100 times more bacterial genes

但事實上，你身上的細菌基因是你本身基因的一百多倍!

playing a role in you or on you all of your life.

在你的身上或體內扮演著某些腳色。

At the best, you're 10 percent human,

最多最多，你只是 10% 的人類，

but more likely about one percent human,

其實更有可能只是 1% 的人類，

depending on which of these metrics you like.

端看你喜歡哪一種度量方法。

I know you think of yourself as human beings,

我知道你認為你自己是人類，

but I think of you as 90 or 99 percent bacterial.

但在我眼中你是 90% 或 99% 的細菌。

(Laughter)

（笑聲）

These bacteria are not passive riders,

這些細菌不只是被動的乘客而已，

these are incredibly important, they keep us alive.

它們非常地重要，它們維持我們的生命。

They cover us in an invisible body armor

它們將我們保護在一層看不見的鎧甲中，

that keeps environmental insults out

隔絕環境刺激，

so that we stay healthy.

因此我們能保持健康。

They digest our food, they make our vitamins,

它們消化我們的食物，製造我們所需的維他命，

they actually educate your immune system

它們還教育你的免疫系統

to keep bad microbes out.

將惡性微生物阻擋於體外。

So they do all these amazing things

它們做了這些了不起的事，

that help us and are vital for keeping us alive,

幫助我們，是我們賴以為生的關鍵，

and they never get any press for that.

但細菌從來沒有因為這些好事上過媒體

But they get a lot of press because they do a lot of

倒是常常因為它們也能導致許多可怕的後果

terrible things as well.

而登上各大版面

So, there's all kinds of bacteria on the Earth

地球上有各式各樣的細菌

that have no business being in you or on you at any time,

有些絕不應該出現在你身上或體內

and if they are, they make you incredibly sick.

如果有，它們會讓你極端難受。

And so, the question for my lab is whether you want to think about all the

因此，我實驗室的研究主題是，所有你想得到細菌做的好事

good things that bacteria do, or all the bad things that bacteria do.

或是所有細菌做的壞事。

The question we had is how could they do anything at all?

並且探討，它們是如何辦到的？

I mean they're incredibly small,

畢竟它們十分的小，

you have to have a microscope to see one.

你必須在顯微鏡底下才能觀察到它們。

They live this sort of boring life where they grow and divide,

它們的生活如此無趣，只是成長與分裂，

and they've always been considered to be these asocial reclusive organisms.

而且它們總被認為是無社會行為的獨行俠

And so it seemed to us that they are just too small to have an impact

所以對我們來說，它們實在是

on the environment

微小到無法對環境產生任何影響

if they simply act as individuals.

尤其它們只是單獨行動的話。

And so we wanted to think if there couldn't be a different

所以我們想探討，

way that bacteria live.

細菌是不是其實用別種方式生存？

The clue to this came from another marine bacterium,

這個問題的線索，來自一種海洋細菌，

and it's a bacterium called Vibrio fischeri.

叫做費氏弧菌 (Vibrio fischeri) 。

What you're looking at on this slide is just a person from my lab

你們在這張投影片看到的，是我實驗室的一個人

holding a flask of a liquid culture of a bacterium,

握著一瓶裝滿這種細菌的培養液

a harmless beautiful bacterium that comes from the ocean,

一種來自海洋，美麗且無害的細菌，

named Vibrio fischeri.

名為費氏弧菌 (Vibrio fischeri)。

This bacterium has the special property that it makes light,

這種細菌的特性是會發光，

so it makes bioluminescence,

它會發出生物螢光，

like fireflies make light.

就如同螢火蟲發出的光。

We're not doing anything to the cells here.

我們沒有對這些細胞做任何事。

We just took the picture by turning the lights off in the room,

我們只是把房間燈關了，然後照了這張照片，

and this is what we see.

這是我們所見到的情形。

What was actually interesting to us

我們尤其感興趣的

was not that the bacteria made light,

不是細菌會發光這件事，

but when the bacteria made light.

而是細菌何時發光。

What we noticed is when the bacteria were alone,

我們注意到當細菌處於單獨環境中，

so when they were in dilute suspension, they made no light.

也就是當它們被稀釋，且懸浮在培養液中時，它們不會發光。

But when they grew to a certain cell number

但是當它們成長至一定數量後，

all the bacteria turned on light simultaneously.

所有細菌會同時開始發光。

The question that we had is how can bacteria, these primitive organisms,

我們疑惑的是，像細菌這麼原始的生物，

tell the difference from times when they're alone,

如何能夠分辨它們現在是單獨

and times when they're in a community,

還是處於群體中

and then all do something together.

然後能夠一起開始從事某種行為。

What we've figured out is that the way that they do that is that they talk to each other,

我們已經發現，這是因為細菌能夠彼此「對談」

and they talk with a chemical language.

它們說的是化學語言

This is now supposed to be my bacterial cell.

假設這個是我的細菌。

When it's alone it doesn't make any light.

當它獨處時，不會發出任何光線。

But what it does do is to make and secrete small molecules

但是它會製造與分泌化學小分子，

that you can think of like hormones,

你可以將它想成荷爾蒙，

and these are the red triangles, and when the bacteria is alone

這邊以紅色三角形代表，當細菌獨處的時候，

the molecules just float away and so no light.

這些分子都擴散開來，因此沒有發光。

But when the bacteria grow and double

但是當這些細菌成長倍增後，

and they're all participating in making these molecules,

它們全都一起製造這些分子，

the molecule -- the extracellular amount of that molecule

這些細胞外分子的含量，

increases in proportion to cell number.

隨著細胞數的增加而增加。

And when the molecule hits a certain amount

等這個分子累積到一定的量之後，

that tells the bacteria how many neighbors there are,

它告訴了細菌，它周圍有多少鄰居，

they recognize that molecule

它們都認識這個分子，

and all of the bacteria turn on light in synchrony.

然後所有細菌，協同一致地開始發光。

That's how bioluminescence works --

這就是它們如何一起發光—

they're talking with these chemical words.

它們藉由這些化學語言交談著。

The reason that Vibrio fischeri is doing that comes from the biology.

費式弧菌的發光現象有它生物學上的原因

Again, another plug for the animals in the ocean,

再一次地，又連結到海洋裡的生物，

Vibrio fischeri lives in this squid.

費式弧菌住在這種烏賊體內

What you are looking at is the Hawaiian Bobtail Squid,

你們現在看到的是，夏威夷截尾烏賊，

and it's been turned on its back,

這是牠的腹側，

and what I hope you can see are these two glowing lobes

我希望你們看得到，那兩個發著光的葉狀突起，

and these house the Vibrio fischeri cells,

它們內部儲藏著這些費式弧菌

they live in there, at high cell number

它們就以非常高的數量，居住在那裡面，

that molecule is there, and they're making light.

這個分子也在那，所以它們發著光。

The reason the squid is willing to put up with these shenanigans

這烏賊之所以願意忍受這些胡鬧行為的原因是，

is because it wants that light.

牠想要這些光線。

The way that this symbiosis works

這個共生行為建立的基礎是

is that this little squid lives just off the coast of Hawaii,

因為這個小烏賊居住在夏威夷的海岸邊，

just in sort of shallow knee-deep water.

牠們生活的海域，大概只有膝蓋一般的深度。

The squid is nocturnal, so during the day

這烏賊是夜行性的，因此白天

it buries itself in the sand and sleeps,

牠把牠自己埋藏在沙中睡覺，

but then at night it has to come out to hunt.

但是到了晚上，牠必須出來獵食。

On bright nights when there is lots of starlight or moonlight

在有許多星光與月光點綴的明亮夜晚，

that light can penetrate the depth of the water

這些光線可以穿透烏賊所住的地方

the squid lives in, since it's just in those couple feet of water.

因為這裡的海水只有數呎深而已。

What the squid has developed is a shutter

這烏賊發展出了一種活葉遮板，

that can open and close over this specialized light organ housing the bacteria.

可以打開或遮蔽由特化發光器官裡的細菌所發出的光線

Then it has detectors on its back

加上這烏賊背上有一些感光裝置，

so it can sense how much starlight or moonlight is hitting its back.

可以用來偵測有多少月光或星光照在牠背上。

And it opens and closes the shutter

然後牠隨之調節遮板的開關，

so the amount of light coming out of the bottom --

因此從牠腹部所放出的光 —

which is made by the bacterium --

是由細菌產生的

exactly matches how much light hits the squid's back,

完全符合照射在這烏賊背部上的光強度，

so the squid doesn't make a shadow.

因此這烏賊不會產生任何影子。

It actually uses the light from the bacteria

牠使用來自細菌的光，

to counter-illuminate itself in an anti-predation device

當成是牠匿蹤裝置中，模擬背景光線的來源，

so predators can't see its shadow,

因此獵食者無法看見牠的陰影，

calculate its trajectory, and eat it.

計算牠的動向，然後吃了牠。

This is like the stealth bomber of the ocean.

就像是大海中的隱形轟炸機一般。

(Laughter)

（笑聲）

But then if you think about it, the squid has this terrible problem

但是如果你深入去思考，這烏賊會有一個可怕的問題，

because it's got this dying, thick culture of bacteria

因為在牠體內，這些黏稠的細菌液正在逐漸死亡，

and it can't sustain that.

牠無法維持這些細菌的生長。

And so what happens is every morning when the sun comes up

因此每天早上當太陽升起後，

the squid goes back to sleep, it buries itself in the sand,

牠將自己埋藏在沙中，進入睡眠，

and it's got a pump that's attached to its circadian rhythm,

而且牠有一個與日夜週期同步的幫浦，

and when the sun comes up it pumps out like 95 percent of the bacteria.

當太陽升起時，它將大約 95% 的細菌排出體外。

Now the bacteria are dilute, that little hormone molecule is gone,

既然細菌被稀釋了，這些小荷爾蒙分子也隨之消失，

so they're not making light --

因此牠們不發光了，

but of course the squid doesn't care. It's asleep in the sand.

但烏賊當然不在意。牠正在沙中睡覺呢。

And as the day goes by the bacteria double,

當一天過去，這些細菌持續分裂生長，

they release the molecule, and then light comes on

牠們釋放出這些分子，然後又開始在晚上發光，

at night, exactly when the squid wants it.

剛好就是烏賊需要光線的時候。

First we figured out how this bacterium does this,

我們先瞭解這些細菌為什麼會有這種現象，

but then we brought the tools of molecular biology to this

然後我們使用分子生物學的方法來研究

to figure out really what's the mechanism.

這個現象下，真正的分子機制為何？

And what we found -- so this is now supposed to be, again, my bacterial cell --

我們發現了 — 再一次，想像這是我的細菌 —

is that Vibrio fischeri has a protein --

費氏弧菌有一種蛋白質

that's the red box -- it's an enzyme that makes

這個紅色的方塊 — 它是製造這

that little hormone molecule, the red triangle.

小荷爾蒙分子（紅三角形）的酵素。

And then as the cells grow, they're all releasing that molecule

當細胞生長時，他們全都釋放這個分子

into the environment, so there's lots of molecule there.

到環境中，因此環境裡有一堆這種分子。

And the bacteria also have a receptor on their cell surface

這些細菌的細胞表面，同時還有一種受器，

that fits like a lock and key with that molecule.

與此分子的構造就如同鑰匙與鎖一般的吻合。

These are just like the receptors on the surfaces of your cells.

它們就如同你身體細胞表面上的受器一般。

When the molecule increases to a certain amount --

當這些分子增加到一定的量時 —

which says something about the number of cells --

它也意味著這些細胞數量的增加 —

it locks down into that receptor

荷爾蒙與受器相結合，

and information comes into the cells

訊息開始向細胞內部傳遞，

that tells the cells to turn on

這個訊息告訴這些細胞開始

this collective behavior of making light.

表現此集體行為，並開始發光。

Why this is interesting is because in the past decade

這個發現之所以有趣，是因為在過去十年間，

we have found that this is not just some anomaly

我們發現這個現象，不只侷限在這些住在大海中，

of this ridiculous, glow-in-the-dark bacterium that lives in the ocean --

滑稽的、會在黑暗中發光的細菌，

all bacteria have systems like this.

所以的細菌都有類似的系統。

So now what we understand is that all bacteria can talk to each other.

所以現在，我們了解所有細菌都可以彼此交談。

They make chemical words, they recognize those words,

它們製造化學文字，也能夠辨認這些文字，

and they turn on group behaviors

然後表現集體行為，

that are only successful when all of the cells participate in unison.

只有當所有細胞一起同心協力才能成功。

We have a fancy name for this: we call it quorum sensing.

我們為這種行為取了一個新潮的名字，稱作：聚量感應。

They vote with these chemical votes,

取決於這些化學物質的數量

the vote gets counted, and then everybody responds to the vote.

加以統計後，所有細胞都要服從最後的結果。

What's important for today's talk

今天演講最重要的一點是

is that we know that there are hundreds of behaviors

我們已經知道有數百種以上的

that bacteria carry out in these collective fashions.

這種細菌的集體行為。

But the one that's probably the most important to you is virulence.

但對你們來說，最關心的應該還是致病性的問題。

It's not like a couple bacteria get in you

並不是說一些細菌進入你體內後

and they start secreting some toxins --

就馬上開始分泌致病毒素，

you're enormous, that would have no effect on you. You're huge.

相對它們來說非常巨大，這點量對你不會有太大的影響。

What they do, we now understand,

我們現在了解，它們是

is they get in you, they wait, they start growing,

先進入你的身體，等待，開始複製成長，

they count themselves with these little molecules,

它們藉由計算這些小分子的數目來估計自身的數量，

and they recognize when they have the right cell number

直到確定有足夠的細胞數為止，

that if all of the bacteria launch their virulence attack together,

一旦這些細菌一起發動致病攻擊，

they are going to be successful at overcoming an enormous host.

它們就能成功攻陷巨大的宿主。

Bacteria always control pathogenicity with quorum sensing.

細菌一向是以「聚量感應」來控制其致病性。

That's how it works.

這就是它們運作的原理。

We also then went to look at what are these molecules --

我們同時也研究了這些分子，

these were the red triangles on my slides before.

這些就是我之前投影片上的小紅三角形。

This is the Vibrio fischeri molecule.

這個是費氏弧菌的分子。

This is the word that it talks with.

這就是它們用以交談的文字。

So then we started to look at other bacteria,

我們開始研究其他細菌，

and these are just a smattering of the molecules that we've discovered.

這些是我們已發現分子中的一小部份。

What I hope you can see

我希望你們看得出來

is that the molecules are related.

這些分子之間是有關聯性的。

The left-hand part of the molecule is identical

就算是不同的菌種

in every single species of bacteria.

它們分子的左半部都是相同的

But the right-hand part of the molecule is a little bit different in every single species.

但是右半部則因不同的菌種而有些許的不同。

What that does is to confer

這個發現證實了

exquisite species specificities to these languages.

細菌的語言有高度的專一性。

Each molecule fits into its partner receptor and no other.

每一種分子只能與其相對受器結合，非常專一。

So these are private, secret conversations.

所以這些交談是私下的、秘密的

These conversations are for intraspecies communication.

只給同種族內溝通交流。

Each bacteria uses a particular molecule that's its language

每一種細菌使用一種特殊分子代表它的語言，

that allows it to count its own siblings.

讓它能夠計算同類的數量。

Once we got that far we thought

一旦我們了解這些，

we were starting to understand that bacteria have these social behaviors.

我們也開始了解細菌有所謂的社交行為。

But what we were really thinking about is that most of the time

但我們真正思考的問題是，多數時間裡，

bacteria don't live by themselves, they live in incredible mixtures,

細菌並不是單獨生活的，它們居住的地方龍蛇雜處，

with hundreds or thousands of other species of bacteria.

跟其它千百種以上的細菌同處一室。