Part 2

Where in the world? Where can you find bacteria? The short answer is… everywhere! Wherever you look, you'll find them doing amazing things. Here are just a few places you can go hunting for bacteria. Ocean Bacteria are found at all depths of the ocean. At the surface, they take in energy from the sun. On the ocean floor, they get energy from chemicals. Air and sky There are bacteria floating in the air around you, as well as in the atmosphere up above your head. Some bacteria even live inside clouds! Rocks Some bacteria can survive inside rocks. There isn't much there to eat, so they grow slowly and reproduce only every 100 years or so. Soil Soil is jam-packed with bacteria. The bacteria that live in soil can turn nitrogen in the air into useful nutrients for plants. This is part of a process called the nitrogen cycle. Nitrogen cycle Nitrogen is a gas that's in the air, in a form plants can't use. Bacteria in the soil turn nitrogen into fertilizer. Plants use the fertilizer to grow. Animals eat plants. Animals pee, poop, and die, and plants die, too. Decomposers, such as worms and fungi, break down the pee, poop, and dead matter back into fertilizer. Other kinds of bacteria can change fertilizer back into nitrogen. At home Your home is full of bacteria, but don't worry—most of them are completely harmless. You might find some dangerous ones on surfaces that aren't properly cleaned. In you! Bacteria play a big role in your body and on your skin. In fact, there are more bacteria cells in your body than human cells! A person carries about 4.4 lb (2 kg) of bacteria in and on their body.

细菌究竟藏在哪里？ 你能在哪里找到细菌呢？ 答案很简单……到处都有！ 不管你往哪看，都能发现细菌在做神奇的事儿。 这就告诉你几个可以搜寻细菌的地方哦。 海洋 海洋所有深度都存在细菌。 在海面，它们从阳光中获取能量。 在海床，它们从化学物质中获取能量。 空气和天空 你周围的空气里，还有头顶上方的大气层里，都飘浮着细菌。 有些细菌甚至住在云朵里！ 岩石 有些细菌能在岩石内部存活。 岩石里没什么食物可吃，所以它们长得很慢，大概每100年才繁殖一次。 土壤 土壤里挤满了细菌。 住在土壤里的细菌能把空气中的氮气，变成植物可以用的养分。 这就是氮循环过程的一部分哦。 氮循环 氮气是空气中的一种气体，原本的形态植物没法利用。 土壤里的细菌把氮气变成了肥料。 植物吸收肥料长大。 动物吃下植物。 动物会排尿、排便、死亡，植物最终也会死亡。 蚯蚓、真菌这类分解者，会把尿液、粪便和遗体分解，重新变回肥料。 还有一些细菌能把肥料变回氮气。 家里 你的家里到处都是细菌，但别担心——它们大部分完全无害。 没清洁干净的物体表面，才可能藏着一些危险的细菌。 就在你身体里！ 细菌对你的身体和皮肤都起到很大作用。 实际上，你身体里的细菌细胞比人体细胞还要多！ 一个人的身体内外一共携带了大约2公斤（4.4磅）细菌呢。

Can a squid glow? The bobtail squid is an amazing animal. It lives in the shallow waters of the Pacific and Indian oceans. At first glance, it appears to be glowing! Can you guess what is really making it shine? Look inside Bobtail squid have special bacteria living in them. Chemicals inside the bacteria make them light up. This is called bioluminescence. Bacteria help the squid hide from animals below by matching the brightness of the waters above. Bobtail squid grow to about 1.2 in (30 mm) long. That's seven times smaller than the average squid. LIGHT IT UP Bobtail squid aren't the only living creatures that glow in the dark. Check out these other super shiners. Mushrooms When fungi like mushrooms make light, we call it fox fire. They use their green glow to ward off hungry predators. Anglerfish Female anglerfish have a body part full of glowing bacteria on their heads. It helps them lure in prey and find mates. Plankton These waves crashing on to a beach in the Maldives, South Asia, are full of tiny bioluminescent plankton. The light confuses their predators.

乌贼会发光吗？ 短尾乌贼是一种超神奇的动物。 它生活在太平洋和印度洋的浅水区。 乍一看，它好像在发光呢！ 你能猜到真正让它发光的是什么吗？ 往体内看看 短尾乌贼身体里住着特殊的细菌。 细菌体内的化学物质让它们发了光。 这就叫作生物发光。 细菌帮短尾乌贼匹配上方海水的亮度，躲开下方的天敌。 短尾乌贼长大后大约只有30毫米（1.2英寸）长。 比普通乌贼小了整整7倍。 发光大集合 会在黑暗里发光的生物可不只有短尾乌贼哦。 来认识一下其他超级发光小能手吧。 蘑菇 当蘑菇这类真菌发光时，我们称它为狐火。 它们靠绿色的亮光吓跑饥饿的捕食者。 安康鱼 雌性安康鱼的头上长了一个塞满发光细菌的器官。 它能帮安康鱼引诱猎物，还能寻找配偶。 浮游生物 南亚马尔代夫拍打到沙滩的浪花里，满是微小的生物发光浮游生物。 亮光能迷惑它们的天敌。

In your body Humans are born without bacteria, but our bodies are quickly inhabited by hundreds of species. Although we often think of bacteria as evil critters that make us sick, most are harmless— and some are even helpful. What's that smell? Most of the bacteria in your body can be found in your gut, where they help you to digest, or break down, your food. But they also have an embarrassing side effect—one you may notice if you eat too many beans… 1 Mouth The first step is chewing! Food must be broken down into smaller parts before it can be used by your body. Muscles in your throat push the food into your stomach. 2 Stomach Food is broken down further by acid in your stomach. The resulting goop is then passed to your small intestine. 3 Small intestine Special snippers called enzymes cut up long food molecules that your body can't use into shorter ones that it can. But the enzymes don't work on big molecules called oligosaccharides found in some foods, such as beans. 4 Large intestine The oligosaccharides pass to your large intestine. Bacteria there can break them down. As they do, the bacteria produce hydrogen and methane gas, which builds up until you fart it out.

你的身体里 人类刚出生时身体里没有细菌，但很快就有几百种细菌住进了我们体内。 虽然我们总觉得细菌是让人生病的坏家伙，但大部分细菌都无害——有些甚至还对我们有益哦。 这怪怪的味道是什么？ 你体内的细菌大部分都住在肠道里，它们帮你消化，也就是分解食物。 不过它们也会带来一个尴尬的副作用——如果你吃太多豆子就会感受到哦…… 1 口腔 第一步就是咀嚼！ 食物必须分解成更小的碎块，才能被你的身体利用。 喉咙的肌肉把食物推进了胃里。 2 胃 胃里的胃酸会进一步分解食物。 分解后的糊状物会被送入小肠。 3 小肠 叫作酶的“小剪刀”，会把身体没法用的长食物分子，切成能利用的短分子。 但酶没法分解某些食物里叫低聚糖的大分子，比如豆子里就有这种物质。 4 大肠 低聚糖会被运到大肠里。 这里的细菌可以分解它们。 细菌分解的时候会产生氢气和甲烷气体，气体越积越多，最后就会变成屁被排出体外啦。

The bad guys Most bacteria are harmless. Some are even helpful. But some can cause us to feel unwell. These harmful bacteria have clever ways of getting from one human host to the next. Cholera Cholera is a terrible illness that spreads easily in places where the drinking water is not clean. In 1855, scientist John Snow discovered that a cholera outbreak in London, England, was caused by something in the water. 1 Bacteria multiply Cholera bacteria multiply inside the warm, moist digestive system of its victim. They attach themselves to the lining of the small intestine and release dangerous chemicals called toxins. 2 Diarrhea The toxins cause the person's body to pump water into the small intestine, making their poop very runny. About half the weight of your poop is bacteria. 3 Cesspool In the 1800s in London, the toilets emptied into underground cesspools. Watery diarrhea helped the cholera bacteria flow easily through any cracks in the cesspool wall. 4 Infected water supply Cholera bacteria seeped through cracks into an underground well. Before people had tap water, they would pump water from wells for drinking. 5 Contaminated water When people drank well water contaminated with cholera bacteria, they became infected. Once John Snow realized what was making people ill, the water pump was shut off. 6 Symptoms pass on This new victim now has diarrhea, too! She will add more cholera bacteria to the cesspool. 7 Cycle continues Cholera infected more drinking water and spread the disease to new victims. Whooping cough Whooping cough bacteria causes a sticky substance called mucus to build up in the lungs. The victim must cough to clear it. This sprays bacteria into the air, and other people breathe it in. Acne Acne bacteria live harmlessly inside little holes in your skin called follicles. When a follicle gets blocked, the bacteria feed on oils that build up, and multiply. Your body fights back with red swelling called inflammation—a pimple!

坏细菌 大多数细菌都是无害的 有些细菌甚至对我们有益 但有些细菌会让我们身体不舒服 这些有害细菌有巧妙的方法，从一个人身上传到另一个人身上 霍乱 霍乱是一种可怕的疾病，在饮用水不干净的地方很容易传播 1855年，科学家约翰·斯诺发现，英国伦敦的霍乱爆发，是水中的某种物质引起的 1 细菌繁殖 霍乱细菌会在感染者温暖湿润的消化系统里繁殖 它们附着在小肠内壁，释放出叫做毒素的危险化学物质 2 腹泻 毒素会促使人体往小肠输送大量水分，让粪便变得非常稀 人的粪便中大约一半重量都是细菌 3 污水池 19世纪的伦敦，厕所污水都排入地下污水池 水样腹泻会让霍乱细菌轻易从污水池壁的裂缝流出去 4 污染水源 霍乱细菌渗过裂缝，进入了地下井水 在有自来水之前，人们都是从井里抽水饮用 5 受污染的水 人们喝了混有霍乱细菌的井水后，就会被感染 约翰·斯诺弄清致病原因后，抽水机就被关闭了 6 传播症状 这个新感染者现在也患上腹泻了！ 她会把更多霍乱细菌带到污水池里 7 循环持续 霍乱污染更多饮用水，把疾病传播给新的感染者 百日咳 百日咳杆菌会让一种叫黏液的黏稠物质在肺部堆积 患者必须咳嗽才能把它清理出去 这会把细菌喷到空气中，其他人就会吸入这些细菌 痤疮 痤疮细菌原本无害地生活在皮肤的毛囊小孔里 当毛囊被堵住，细菌就会以堆积的油脂为食，不断繁殖 你的身体会发起反击，形成红肿的炎症——也就是痘痘！

Your body's defenses Your body has all sorts of ways to defend itself against harmful microbes, or germs. Together, these defenses make up your immune system. Your immune system's first line of defense is your skin. Cut Your skin is your biggest organ. It's a tough layer of armor around your body. When it's cut, the tissue underneath is exposed to germs, which can cause infection. The blood in your body flows through a system of tubes called arteries. Inside your blood are different types of white blood cells, all with different ways of fighting germs. Dangerous bacteria and germs can't get through your skin. When you get a cut, your immune system sends more bacteria-fighting blood to the area, causing your skin to become red and swollen. Bacteria can produce toxins that hurt your body. This type of white blood cell releases chemicals to fight those toxins. This kind of white blood cell releases chemicals called antibodies that kill or stun invading germs. Then the macrophages can easily gobble them up. ALLERGIES When your immune system attacks something that isn't harmful, such as pollen, it's called an allergy. Having an allergy to pollen is called hay fever. OTHER DEFENSES Your immune system has a few other tricks that help to stop an infection in its tracks. Fever When you have a fever, your body temperature is higher than normal. Fevers fight germs and help white blood cells work better. Sneezing Microbes in your nose can make you sneeze. Sneezing helps to expel the germs, keeping you healthy. Tears Germs can irritate your eyes. The tears they cause try to flush them out.

身体的防御系统 你的身体有很多种方法对抗有害微生物，也就是病菌 这些防御方式共同组成了你的免疫系统 免疫系统的第一道防线就是你的皮肤 伤口 皮肤是你身体最大的器官 它是包裹你身体的一层坚硬铠甲 当皮肤被划破，皮下组织就会暴露在病菌面前，可能引发感染 体内的血液通过叫做动脉的血管系统流动 血液里有不同种类的白细胞，各自有不同的方法对抗病菌 危险的细菌和病菌没法穿透完好的皮肤 当你划破皮肤，免疫系统会运送更多杀菌血液到伤口，让皮肤变得红肿 细菌会产生伤害身体的毒素 这类白细胞会释放化学物质对抗这些毒素 这类白细胞会释放叫做抗体的化学物质，杀死或击晕入侵的病菌 之后巨噬细胞就能轻松把它们吃掉了 过敏 当免疫系统攻击花粉这类原本无害的物质时，就叫做过敏 对花粉过敏被称为花粉热 其他防御方式 免疫系统还有其他妙招，能及时阻止感染 发烧 发烧的时候，你的体温会比正常水平高 发烧能对抗病菌，还能帮助白细胞更好地工作 打喷嚏 鼻子里的微生物会让你打喷嚏 打喷嚏能帮你排出病菌，让你保持健康 眼泪 病菌会刺激你的眼睛 刺激产生的眼泪会把病菌冲洗出去

The story of antibiotics There are ways to avoid getting infected by bacteria, such as washing your hands and not touching your eyes and mouth. If you already have an infection, however, your doctor might give you medicine. Medicines that fight bacteria are called antibiotics. Amazing discovery There used to be no treatment for deadly bacterial infections such as pneumonia. Then, bacteriologist Alexander Fleming accidentally discovered something amazing. In 1928, before leaving for a trip, Alexander Fleming set up bacteria samples to grow in petri dishes while he was away. When he returned, one sample looked very strange… Fleming had left his lab a little messy. Different substances had gotten into the petri dishes. One of them had some mold in it. Mold is a type of fungus, and it had a surprising effect on the bacteria. Fleming figured out what had happened. The hungry mold, called penicillium, had killed nearby bacteria competing for nutrients by releasing a molecule we now call penicillin. The penicillin had made the bacteria cells pop. Over time, scientists figured out how to separate the penicillin from its mold. Penicillin is now used to treat bacteria infections all over the world. But then... BACTERIA FIGHT BACK! Bacteria don't give up easily. They can get used to an antibiotic, causing it to stop working. This is why scientists are always on the hunt for new antibiotics. Antibiotic mostly works An antibiotic can kill bacteria, but some cells that are slightly different, or mutated, survive. Antibiotic stops working The mutated bacteria grow and multiply. The old antibiotic doesn't work too well on these bacteria. New antibiotic works New antibiotics are found that kill the mutated bacteria. But new mutations continue to form...

抗生素的故事 有很多方法可以避免细菌感染，比如洗手、不要触碰眼睛和嘴巴。 不过如果你已经感染了，医生可能会给你开药物治疗。 对抗细菌的药物就叫做抗生素。 神奇的发现 过去像肺炎这样致命的细菌感染是没有治疗方法的。 后来细菌学家亚历山大·弗莱明意外有了惊人发现。 1928年，亚历山大·弗莱明出门旅行前，把细菌样本放在培养皿里培养后就离开了。 他回来后，发现一个样本看起来非常奇怪……弗莱明的实验室原本有点乱。 不同的杂质掉进了这些培养皿里。 其中一个培养皿里长出了一些霉菌。 霉菌是真菌的一种，它对细菌产生了出人意料的影响。 弗莱明弄清楚了事情的经过。 这种饥饿的霉菌叫青霉菌，它会释放一种我们现在称之为青霉素的分子，杀死和它争夺营养的周边细菌。 青霉素让细菌细胞破裂死亡。 久而久之，科学家研究出了从霉菌中分离青霉素的方法。 如今全世界都在用青霉素治疗细菌感染。 但后来……细菌开始反击了！ 细菌可不会轻易认输。 它们能适应抗生素，让抗生素失去效果。 这就是为什么科学家一直在寻找新型抗生素。 抗生素通常有效 抗生素可以杀死细菌，但有一些略有不同，也就是发生突变的细菌存活了下来。 抗生素失效 突变细菌生长并大量繁殖。 旧抗生素对这些细菌已经没什么效果了。 新抗生素起效 人们找到了能杀死突变细菌的新型抗生素。 但新的突变还在不断产生……