Chances are, in your life, you’ve had the common cold before.
你们以前可能都得过普通感冒
It can cause sneezing and coughing
它会引起打喷嚏和咳嗽
and can make you feel awful
让你感觉不舒服
The worst thing about the common cold is that
对于普通感冒最糟糕的事情莫过于
you can take medications to help with the symptoms,
你可以服用药物来减轻症状
but you really can’t treat the actual cold with antibiotics
但是你绝对不能像治疗球链菌性喉炎或者发炎的牙齿一样
like you would a strep throat infection or an infected tooth.
用抗生素来治疗真正意义上的感冒
Why? Well let’s talk about what causes it:
为什么呢？ 那么我们来谈谈感冒是什么引起的
a virus
是一种病毒
The common cold is caused by a virus.
普通感冒是由病毒引起的
And while all living things are made of 1 or more cells
根据现代细胞学的理论
see the modern cell theory
虽然所有生物都是有单一或者多个细胞组成
viruses are not cells.
但病毒却不是细胞
Viruses aren’t technically classified as living things
严格说来 病毒不属于生物
since they lack many characteristics of life,
因为它们缺少很多生物的特征
but there is debate in calling them nonliving as well.
但称它们为非生物也存在争议
Medications like antibiotics attack bacteria
抗生素之类的药物会攻击
like E.coli which are living cells.
像大肠杆菌这样的活细胞细菌
Anti-fungal medications can be used on fungi
抗真菌药物可以用于真菌感染
like athlete’s foot which are made of living cells
比如导致脚气的活细胞真菌
Viruses are not bacteria or fungi.
病毒既不是细菌也不是真菌
You can’t classify a virus as a prokaryote or a eukaryote either
你不能把病毒归类为原核生物或真核生物
because it’s not a cell.
因为它不是细胞
So what is their structure like?
那么病毒的结构是怎样的呢？
First of all, viruses are much, much smaller than cells.
首先病毒要比细胞小得多
You typically are going to need an electron microscope in order to see a virus.
你通常需要一个电子显微镜才能看到病毒
Viruses come in many shapes.
病毒有各种的形状
Our favorite one to draw is the bacteriophage!
我们最喜欢画的是噬菌体病毒
It sounds very fancy, but it is a type of virus that tends to attack bacteria.
听起来很炫酷 但它是一种总是攻击细菌的病毒
Despite this being our favorite to draw,
尽管这是我们最喜欢画的一种病毒
know the shape of viruses vary greatly.
但是要知道病毒的形状千差万别
One thing all viruses have in common is
所有的病毒都有一个共同点
that they have some type of genetic material.
那就是它们有某种遗传物质
This genetic material can be in the form of DNA or RNA.
这种遗传物质可能是以DNA或RNA的形式呈现出来
Viruses usually have some kind protein coat, also known as a capsid.
病毒通常有某种蛋白质外壳 也称为衣壳
The capsid can protect that DNA or RNA genetic material.
衣壳可以保护遗传物质DNA或RNA
Viruses can also can have other structures.
病毒也有其他结构
Some viruses package special enzymes with them.
一些病毒含有特殊的酶
Some viruses have an outer envelope.
一些病毒有外膜
These additions can be useful to the virus in virus replication.
这些添加物有助于病毒的繁殖
One thing that makes virus replication, or reproduction,
病毒复制或繁殖的独特之处
unique is that they can’t replicate without a host.
在于没有宿主 它们就无法复制
And it’s their reproducing that tends to be a problem for its host:
正是它们的繁殖给宿主带来了问题
whether the host is you ,in the case of a common cold,
无论是得了普通感冒的人
or an insect, plant, or this bacterium.
还是昆虫 植物 亦或是这种细菌
Viruses tend to be very specific for the host that they’re going to go infect,
病毒往往对要去感染的宿主非常情有独钟
but anything that is alive can be a host,
但任何生物都可能成为宿主
because cells have the machinery viruses need in order to replicate.
因为细胞有病毒复制所需要的机制
We’re going to talk about two types of viral replication cycles.
我们要讨论的是两种病毒复制循环
The first one is the lytic cycle.
第一个是裂解循环
In the lytic cycle, the virus, remember very selective, attaches to a host cell.
在裂解循环中 病毒非常有选择性地 附着在宿主细胞上
It often binds to a receptor that this cell has
它经常与细胞的受体结合
which gives it access to attach
使它可以附着在那里
The virus can inject either its DNA or RNA,
然后 根据病毒携带的遗传物质
depending on what kind of genetic material it has, into the cell.
病毒会向细胞注入DNA或者RNA
Some types of viruses are actually taken inside the cell themselves.
有些类型的病毒实际上是被细胞整个吸收进去的
Now you would think the cell would notice
那么你肯定会认为细胞会察觉到
viral DNA or RNA or an entire virus that has been taken in,
病毒的DNA或RNA或整个被吸收的病毒
but in many cases it does not.
但在多数情况下细胞无法察觉
It takes the genetic material from the virus
它吸收了病毒的遗传物质
and it starts following the instructions,
然后开始遵循指令
which in this case is very bad,
这样情况就变得非常糟糕了
because the instructions tell it to make copies of the virus.
因为指令告诉它去复制病毒
The cell uses its own resources to start building.
细胞用自己的资源开始工作
It starts making so many copies of the virus that
它开始大批量地复制病毒
it can cause the cell membrane of the host to rupture, explode, lyse!
以至于造成宿主细胞膜破裂 爆裂和溶解！
So what happens is now these new viral copies get out of the cell,
接着这些复制的新病毒会脱离原来的细胞
and they go and infect other cells.
去感染其它的细胞
This is known as the lytic cycle.
这被称为裂解循环
By the way,
顺便说一下
the lysing of the cell membrane is a very bad thing for the cell.
细胞膜的溶解对细胞是非常有害的
The cell cannot survive without its cell membrane.
没有细胞膜 细胞就不能存活
The other cycle is called the lysogenic cycle,
另一个循环称为溶原化循环
and I like to remember this is the longer word
我想记住这个更长的词
so I like to think of this as the longer, sneaky cycle.
所以我把它看作是个潜伏周期更长更隐蔽的循环
Viruses that go through this cycle
经历这个循环的病毒
tend to do the same thing at the beginning.
在开始的时候总是做同样的事情
They inject their genetic material,
它们注入它们的遗传物质
but this time, the genetic material stays hidden in the host’s genetic material.
但这一次 遗传物质隐藏在宿主的基因遗传物质中
What happens is that when the host makes new cells,
当宿主产生新的细胞时
it replicates its own genetic material and the viral genetic material.
它复制自己的遗传物质和病毒遗传物质
Then those daughter cells make new cells,
然后这些子细胞产生新的细胞
and they also replicate their own genetic material and the viral genetic material.
它们也复制自己的遗传物质和病毒遗传物质
And so on.
如此重复下去
That is the lysogenic cycle.
这就是溶原化循环
That may not seem like a problem,
这似乎没什么大问题
but it really becomes one if the virus gets triggered to
但如果它在某个点被触发
go into the lytic cycle from that point,
进入裂解循环 它就会变成大问题
because then all those cells that had
这是因为 所有那些拥有病毒遗传物质的细胞
the viral geneticmaterial can start assembling viruses.
都可有能开始复制病毒
As far as what triggers it to go into the lytic cycle，
至于什么会触发它进入裂解循环
it can vary.
原因各有不同
It could be a chemical trigger for example
例如 它可能是一种化学物质的触发
or a lack of food for the host.
或者是宿主缺乏营养
Going back to the common cold,.
话题再回到普通感冒上
a lot of times it has to run its course
多数情况下它只能顺其自然
Your immune system will typically take care of it
你的免疫系统通常会解决这个问题
and medications can help the symptoms
而药物可以缓解症状
so that they don’t feel not as bad.
让他们感觉没有那么糟糕
But, unfortunately,
但不幸的是
some viruses are extremely complicated,
有些病毒极其复杂
like HIV,
比如HIV病毒
a virus that can lead to AIDS.
它是一种会导致艾滋病的病毒
Like most viruses, it is very specific.
像大多数病毒一样 它也非常专一
It binds to a CD4 glycoprotein that
它与特定细胞表面的
is found on the surface of specific cells
CD4糖蛋白结合
such as Helper T cells.
比如 Helper T细胞
The problem about this particular target is
关于这个特殊目标的问题在于
that Helper T cells play an important role
helper T细胞在免疫系统中
in protecting the body in the immune system.
起着保护身体的免疫系统的重要作用
Since HIV goes after these immune cells,
因为HIV病毒会攻击这些免疫细胞
it can make a person that is infected with HIV
这就使一个感染HIV病毒的人
vulnerable to other infections.
容易受到其它感染
There are medications that have been developed
目前已经研发出一些药物
to help keep HIV from replicating as quickly,
来帮助延缓HIV病毒的复制
and there continues to be research looking into ways
目前仍然在继续研究
to keep the virus from attaching
寻找阻止病毒附着的办法
because if the virus can’t attach
因为如果病毒不能附着
it can’t insert its genetic material.
它就不能注入它的遗传物质
A problem that continues to be a challenge is that
还有一个具有挑战性的问题是
many viruses, including HIV, can mutate.
许多病毒 包括艾滋病毒 是会变异的
So a treatment developed against a certain virus type
因此 针对某种病毒类型研发的疗法
may not work on a mutated form.
可能对变异的病毒不起作用
So with our talk about viruses, you might wonder,
在我们谈论病毒的时候 你可能会寻思
“Is there anything positive about viruses?”
“病毒难道没有好的一面吗？”
Well, some viruses can play a useful role in gene therapy.
额 病毒可以在基因疗法中发挥有益的作用
Definitely something to explore more.
而且肯定还有更多值得探索的东西
Also, remember how we mentioned that
另外 记住我们之前提到过的
viruses can go after other organisms like insects for example
病毒可以攻击其它生物 比如昆虫
A virus that targets pest insects .
一种针对害虫的病毒
could be an alternative to a chemical pesticide
可能成为化学杀虫剂的替代品
One such example virus that you may want to explore
那你可能想要探索的病毒
is the Nuclear Polyhedrosis Virus.
是像核多角体病毒这样的病毒
Still, it’s important to consider that whenever talking about any kind of pesticides,
尽管如此 重要的是 每当谈到任何一种杀虫剂时
chemical or viral,
无论是化学杀虫剂还是病毒杀虫剂
there could be consequences in the ecosystem.
都要考虑到可能会对生态系统造成的影响
Well, that’s it for the Amoeba Sisters
好了 这就是本期阿米巴姐妹的内容
and we remind you to stay curious!
我们希望你能保持好奇心
[Music]
[音乐]