They cover us in an invisible body armor that keeps environmental insults out so that we stay healthy. 它们是我们身上的无形盔甲，阻断来之环境的伤，保持我们的健康。

　　They digest our food, they make our vitamins, they actually educate your immune system to keep bad microbes out. 它们消化食物，制造维他命，它们还指导你的免疫系统将有害微生物阻挡在体外。

　　So they do all these amazing things that help us and are vital for keeping us alive, and they never get any press for that. 它们尽心尽职干活，帮助我们，维护我们的生命，却从没有因此得到过报道。

　　But they get a lot of press because they do a lot of terrible things as well. 反而却因为它们同时做的许多坏事而时常见报。

　　So, there's all kinds of bacteria on the Earth that have no business being in you or on you at any time, 地球上有无数种细菌，有些在任何时候都绝对不应该出现在你的体内体表，

　　and if they are, they make you incredibly sick. 然而假如你不幸遇到了，那你一定会病得很厉害。

　　And so, the question for my lab is whether you want to think about all the good things that bacteria do, or all the bad things that bacteria do. 所以, 我们实验室研究的问题是，正是你想知道的，细菌做的所有好事或者细菌做的所有坏事。

　　The question we had is how could they do anything at all? 我们曾经提出一个疑问: 它们究竟是怎么做到的?

　　I mean they're incredibly small, you have to have a microscope to see one. 我指的是，它们是那么细微，用显微镜才能看到一个。

　　They live this sort of boring life where they grow and divide, and they've always been considered to be these asocial reclusive organisms. 它们的生活好像只是单调乏味的成长与分裂，而且长久以来被认为是不善社交的隐居生命体。

　　And so it seemed to us that they are just too small to have an impact on the environment if they simply act as individuals. 所以在我们看来，它们实在是太渺小，如果单枪匹马，根本到无法对环境产生任何影响。

　　And so we wanted to think if there couldn't be a different way that bacteria live. 所以我们正在探讨细菌是不是有着特殊的生存方式。

　　And the clue to this came from another marine bacterium, and it's a bacterium called Vibrio fischeri. 解答这个问题的线索，来自一种叫做费氏弧菌的海洋细菌。

　　And what you're looking at on this slide is just a person from my lab holding a flask of a liquid culture of a bacterium, 你们在这张幻灯看到的，是我实验室的一个工作人员握着一瓶装满这种细菌的培养液，

　　a harmless beautiful bacterium that comes from the ocean, named Vibrio fischeri. 这是一种来自海洋的、美丽而且无害的细菌，叫做费氏弧菌。

　　And this bacterium has the special property that it makes light, so it makes bioluminescence, like fireflies make light. 这种细菌的特性是会发光，产生生物荧光，像萤火虫一样。

　　So we're not doing anything to the cells here. 我们没有对这些细胞做任何处理。

　　We just took the picture by turning the lights off in the room, and this is what we see. 我们只是把房间灯关了，然后照了这张照片，这是我们所见到的情形。