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蓝藻如何占领世界 – 译学馆
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蓝藻如何占领世界

How Cyanobacteria Took Over The World

journey to the microcosmos
《微观旅途》
Cyanobacteria have a deceiving sense of the understated about them.
蓝藻的低调似乎带有一丝欺骗
Compared to some of the complex organisms
同我们在《微观旅途》栏目中
we’ve featured on Journey to the Microcosmos,
介绍的一些复杂生物相比
these blue-green bacteria seem almost
这些蓝绿色细菌的形态
basic in their morphology and habits.
生活习性似乎最简单
They glide, divide,
它们会滑动 分裂
and photosynthesize.
还会进行光合作用
Oh, and they get eaten a bunch too.
对了 它们也会被成群的吃掉
But you do not need to be complicated to be important.
但生物的重要性并非因其复杂的结构
Ecosystems are built on primary producers like cyanobacteria.
初级生产者 如蓝藻 是生态系统的基础
The energy they translate from the sun into chemical stores
它们把太阳能转化为化学能
gets passed up the food chain,
使能量流入食物链
sustaining life of all sizes.
供养着各种类型的生物
And long ago, some eukaryotes gained their own
很久以前 一些真核生物通过吞噬蓝藻
photosynthetic abilities by absorbing cyanobacteria
使自身获得光合作用的能力
and endorsymbiotic event had set the stage for the evolution of plants.
“内共生”为植物进化提供了舞台
And plants are a pretty big deal.
植物也十分重要
Cyanobacteria, however, are more than just a prologue for the story of complex lifeforms.
然而 蓝藻不仅仅是复杂生命体进化故事的序章
You might say they are the creative forces behind that tale.
你可以说 它们驱动了生命进化进程
Billions of years ago, these tiny, seemingly innocuous organisms
数十亿年前 这些微小 似乎无害的生物
brought something new to the planet,
给地球带来了一些新的东西:
an innovation that would create massive changes in their environment
给它们的生活环境带来翻天覆地的变化
and set the stage for eons of remarkable life to come.
为即将到来的 万物繁荣的时期搭建舞台
This is the story of the Great Oxidation Event,
这就是大氧化事件
and how in the process of destroying the world as it existed,
以及世界在涅槃重生的过程中
cyanobacteria created the Earth as we know it now.
蓝藻是如何重塑了我们现在所知的地球
The bulk of this tale takes place about 2.5
故事的爆发点大概发生在25亿年前
billion years ago, at the end of the Archean Eon
也就是太古宙末期(新太古代)
that had started about 1.5 billion years before.
此前 太古宙已存在了15亿年
This vast stretch of time
在这段漫长的时间中
included huge milestones for our planet
地球发生了许多重大的里程碑事件
including the early days of the microcosmos.
早期的微观世界亦如此
But the Archean Earth looked very different from ours.
太古宙时期的地球与现在大不相同
The planet’s crust was stabilizing,
那时 地球地壳稳定
and the oceans were filled with dissolved iron.
溶解铁填满了海洋
Most importantly though,
最重要的是
the world was anoxic,
世界处于厌氧环境
meaning it had almost no oxygen.
意味着 地球上几乎没有氧气
And because life reflects the environment it fills,
况且 因为生命体是其生活环境的反映
the earliest creatures on our planet were anaerobic microorganisms,
所以地球最早的生物都是厌氧微生物
built to withstand and thrive in an oxygen-less environment.
它们适应了低氧环境 并在其中不断繁衍生息
Some of these organisms may have been phototrophic,
其中也有一些光养性微生物
but their photosynthetic machinery relied on
但它们的光合作用机制
iron and sulfide in place of water,
依赖于水中的铁和硫化物
similar to bacteria like thiospirillum that thrive in anoxic conditions today.
就像今天在厌氧环境中生存的硫螺菌属
But for all the dramatic changes in Earth and in life
但在太古宙时期
that took place during the Archean Eon,
地球及生物体发生的所有巨变
the real transformation was only just beginning.
仅仅只是真正转变的开端
We don’t know quite when cyanobacteria emerged,
我们不知道蓝藻出现的时期
just that it’s some time before 2.5 billion years ago.
可能在25亿年前的某个时间吧
And when they did, cyanobacteria brought something new to the photosynthetic mix:
当蓝藻出现时 它们为光养混合模式带来了新变化:
they used light to split water into its chemical components: hydrogen,
它们利用光来分离水 将其转化为氢
which could then be used to make other energy-storing compounds,
用以生成储能化合物
and oxygen, which was released into the environment as a waste product.
另一产物——氧气 作为废气释放到环境中
This simple chemical reaction is the source of the Great Oxidation Event,
这个简单的化学反应就是大氧化事件的起因
which you might also hear called the Great Oxygenation Event:
你也许听过另一个名字 大氧合事件
an accumulation of oxygen in a previously anoxic world.
也就是在先前的无氧环境中 积累大量氧气
That reaction would go on to become one of the most important ones to life,
后来 这个反应成为生物体最重要的反应之一
the source of the very oxygen you are breathing now.
你此刻呼吸的每一口氧气都来源于此
And remarkably, cyanobacteria were not just the first organisms
值得注意的是 蓝藻并不是第一种
to evolve oxygenic photosynthesis.
进化成进行含氧光合作用的生物
As far as we know, on our planet anyway,
据我们目前所知 至少在地球上是这样
they are the only organisms that do so.
蓝藻是唯一进行含氧光合作用的微生物
Other photosynthetic bacteria don’t produce oxygen.
其他的光养性细菌并不产生氧气
And the eukaryotic organisms that gained the capacity for photosynthesis
真核微生物通过与蓝藻内共生
did so by co-opting the talents and machinery of endosymbiotic cyanobacteria.
借助蓝藻 获得了光合作用的能力
And as wonderful as that is now,
和现在一样神奇的是
back at the end of the Archean eon,
在太古宙末期(新太古代)
oxygenic photosynthesis didn’t just make cyanobacteria unique,
含氧光合反应不仅使蓝藻变得特别
it made them catastrophic.
也使它们极具毁灭性
Oxygen is great–if you are evolved
如果进化成适应氧气 且利用氧气
to tolerate it and to use it.
那氧气就是个好东西
But for the anaerobic microorganisms
但对于厌氧微生物
specifically evolved for a world without oxygen,
尤其是进化为极其厌氧的微生物
this newfangled molecule was toxic.
这种新生成的分子是有毒的
The species that survived the Great Oxidation Event likely did so
在大氧化事件中 某些物种可能
by finding oxygen-less sanctuaries.
通过寻找低氧避难所 才得以存活
And meanwhile, cyanobacteria continued pumping out oxygen.
与此同时 蓝藻仍在不断地释放出氧气
Yes, they are tiny,
是的 它们很微小
and the amount of gas they produce is even tinier.
释放出的气体可能更少
But with hundreds of millions of years
但历经几百万年的时间
and many many organisms,
以及大量的微生物进行反应
all of those reactions added up,
它们产生的氧气加起来
affecting not only the lives of their fellow microbes
不仅危及了其他微生物生存
but also the chemistry and climate of the entire planet.
还影响了整个地球及其气候变化
For one, cyanobacteria might be responsible for setting off a series of ice ages.
首先 蓝藻可能是冰河时代开启的原因
As they consumed carbon dioxide and produced oxygen
因为它们消耗了二氧化碳 产生了氧气
that reacted with methane,
氧气又与甲烷反应
they cut down on the planet’s stock of greenhouse gases
使地球上的温室气体含量下降
and dropped temperatures to glacial levels.
地球气温降至冰河时期水平
As you might imagine, these early ice ages were not particularly hospitable for life,
你可以想象 早期的冰川时代并不适合生物生存
including for cyanobacteria,
其中也包括蓝藻
coupled with the anaerobic microbes
以及厌氧细菌
that died due to all of that oxygen in the atmosphere,
后来它们又因大气中积累的氧气灭绝
the Great Oxidation Event is responsible for an extinction
大氧化事件导致了这次灭绝
so ancient that we don’t have the tools
因其年代久远 我们没有任何工具
or physical evidence to even fully describe it.
或是实物证据来完整描述这次灭绝
But life still managed to endure.
但是生命体仍在努力适应着
And as it did, the oxygen produced by cyanobacteria
在此过程中 蓝藻细菌产生的氧气
would go on to form our planet’s ozone layer,
继续积累 形成地球臭氧层
shielding the survivors from dangerous ultraviolet wavelengths of light.
保护了幸存者 使其免受紫外线的伤害
Moreover, the availability of oxygen in the water and air
此外 空气和水中的可利用的氧气
would go on to make aerobic metabolism possible,
使生物的有氧代谢成为可能
providing organisms more energy than anaerobic metabolism ever could
比起无氧代谢 为微生物提供更多的能量
and thus the capacity for more complex life.
甚至有可能进化出更复杂的生命体
This intertwined story of destruction and evolution
这个错综复杂的毁灭 进化 演变的故事
is built on evidence scientists have gathered from geological and biological sources.
以科学家收集的地质及生物证据为基础
Some parts are etched in rocks,
一些证据被刻蚀在岩石上
like the banded iron formations formed by oxygen reacting with iron in the ocean.
比如氧气和铁 在海洋中反应形成带状铁层
And other parts are encoded in the genes of modern day cyanobacteria,
其他证据被编码在现代蓝藻的基因中
whose sequences and machinery elucidate
蓝藻的基因序列和生命机理
what their ancient counterparts may have looked like.
说明了它们祖先可能的样子
But characterizing the lives of microbes that existed billions
但要对数十亿年前的生存的微生物分类
and billions of years ago is really, really hard,
是十分艰难的
especially because we haven’t uncovered many Archean fossils.
尤其是因为 我们并未发现许多太古宙时期的化石
One recent paper begins with the following confession:
最近有一篇论文 是以这样的自白开头的:
“Writing about early microbial evolution is a daunting task,
“研究早期微生物的进化是一项艰难任务
so it was possibly unwise to agree to do it.”
所以 支持这个研究或许是不明智的”
And as you dig through the research on the subject,
当你深入研究这个课题时
that honest evaluation rings true.
这一真实评价也是正确的
There are many gaps in our understanding of the Great Oxidation Event,
我们对大氧化事件的理解还有许多空白
gaps built on unanswered fundamental questions like,
我们对一些基本问题仍没有答案
“how did photosynthesis even evolve?”
比如“光合作用是如何进化的?”
We alluded to one of the most important gaps earlier.
我们之前也提到了最重要的问题之一:
It’s the question of when cyanobacteria first appeared,
蓝藻在什么时候首次出现呢
and that question is key to understanding
这个问题的答案是
how they caused the Great Oxidation Event.
理解它们如何造成大氧化事件的关键
If that event began shortly after the evolution
如果在蓝藻进化 含氧光合作用出现不久后
of cyanobacteria and oxygenic photosynthesis,
就发生了大氧化事件
then it all seems relatively straightforward:
那么一切都简单明了:
the cyanobacteria produced oxygen,
蓝藻产生了氧气
the oxygen accumulated, and catastrophe ensued,
氧气不断积累 灾难也随之而来
but some evidence suggests
但有一些证据显示
that cyanobacteria emerged well before the accumulation of oxygen on Earth,
在地球积累氧气之前 蓝藻就已经出现
and if that’s the case, then we have to ask:
如果是这样 那我们就得问:
“What took so long for the Great Oxidation Event to begin?”
“为何大氧化事件 经过这么长时间后才开始?”
Maybe there was a geological delay of some sort.
也许是某种地质上的延迟
or maybe oxygenic photosynthesis wasn’t the only cyanobacterial innovation:
或许含氧光合作用 并不只是蓝藻的创新:
maybe after their first appearances on the planet,
或许它们首次在地球出现后
they developed some other trait
发展出一些其他特征
that bumped their oxygen production up even more.
使它们释放更多的氧气
One group of scientists investigated that very possibility
一组科学家研究了这种可能性
and came to a possible explanation
且得出了一种可能的解释
that we don’t often associate with bacteria:
这种解释通常不会与细菌联系起来:
multicellularity.
多细胞结构
Some modern cyanobacteria species form filaments of individual cells,
一些现代蓝藻物种 形成了单细胞的细胞丝
a few of which even take on specialized functions
其中一些细丝甚至有专门的功能
like nitrogen fixation.
比如固氮作用
These scientists traced the origins of that trait too
科学家也追踪了在大氧化事件前
before the Great Oxidation Event.
这些特征的起源
So maybe multicellularity allowed cyanobacteria
因此 也许多细胞结构
to not only better contend with the challenges of their environment,
不仅让蓝藻更好地应对环境挑战
but to produce more oxygen than before.
同时还能产生更多的氧气
And perhaps this was the added trait needed to,
也许就是这种新特性
say, allow a new kind of bacteria to take over an entire world..
使得新型细菌接管整个世界
a claim over our planet that they have, in many ways, never given up.
从多个方面来说 它们从未放弃统治地球的宏图
Of course, that idea is scientific conjecture built on the available evidence,
当然了 这个想法是以现存证据为基础的科学推测
which means it is still subject to debate.
也就意味着 这个问题仍存在争议
But the seemingly simple question underlying it,
但它背后还有一个看似简单的问题
the question of when cyanobacteria evolved,
蓝藻从何时开始进化的问题
reflects what’s so important about the Great Oxidation Event in general:
反映了大氧化事件的重要之处:
that questions of biology and geology and climate
这个问题有关生物学 地质学和气候
are so intertwined
是如此错综复杂
that to understand the history of this planet,
若是要了解这个星球的历史
we have to piece together the history of the microcosmos.
就得先拼凑出微观世界的历史
And if something as small as cyanobacteria
如果像蓝藻这样小的生物
can set off a catastrophe of extinction and ice,
都能引发灭绝的灾难 开启冰川时代
well, then what will the planet look like
那么 当人类统治地球的时候
when we’re through with it?
地球又会是什么样子呢
Thank you for coming on this journey with us
感谢你们与我们一起
as we explore the unseen world that surrounds us.
踏上探索周围未知世界的旅程
The Stentor coeruleus pins have been restocked.
东湖天蓝喇叭虫的视频已上传
There’s a link in the description so you can check that out.
你可以点击简介中的链接
Thanks to everybody who’s sporting one of their favorite
感谢每个在背包或是夹克上
microorganisms on their backpack or jacket now.
展示他们最喜欢的微生物的爱好者们
And thank you, also, to all of these people
同时也感谢所有这些人
who make this show possible.
是他们让本节目成功创办
So, if you like what we do, you can thank them for that.
如果你喜欢我们的节目 那就谢谢他们吧
What a wonderful group of people,
他们真的特别棒
that allow us to explore these big
是他们让我们得以探索
weird mysteries of life on this planet.
这个星球上生命的神秘之处
If you want to see more from our Master of Microscopes James,
如果想要了解更多《显微镜大师:James》
you can check out Jam and Germs on Instagram,
可在Ins上搜索Jam & Germs
and if you want to see more from us
如果您想收看更多本节目
I bet you can figure out how to subscribe.
肯定知道如何订阅吧

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视频概述

小小的蓝藻为何给地球带来灭顶之灾?

听录译者

收集自网络

翻译译者

刘小贵

审核员

审核员 V

视频来源

https://www.youtube.com/watch?v=ps2GlGs8oso

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