Part 4

Micro chefs Who would have thought microbes could also be helpful in the kitchen? We've been using fungi and bacteria in a process called fermentation for thousands of years. This process makes food last longer and makes it more delicious. Fermentation Yeasts are a type of fungus made of one cell. They change sugars into other molecules, such as alcohol and carbon dioxide gas, through fermentation. This is why people use yeast to make drinks like wine. 1 The first step in making wine involves crushing a lot of grapes. Traditionally people did this by stamping on the grapes with their feet! 2 Grapes have natural yeast on their skins. Crushing them mixes the yeast with the sugar inside. This starts the process of fermentation. 3 The yeast dies when the amount of alcohol becomes too high for it. If the wine is bottled before the yeast dies, bubbles of carbon dioxide are trapped, making it fizzy. Favorite foods Fermentation is used in a few unexpected products. Here are some of the world's favorite fermented foods. Bread Yeast is added to bread dough to make bubbles of carbon dioxide. The gas is trapped in the dough, and that's what makes bread light and fluffy. The holes in bread are made by carbon dioxide gas. Kimchi Kimchi is a traditional Korean side dish made from cabbage and other vegetables. Bacteria ferment the cabbage to give it a sour taste. Cheese When one of the sugars in milk, called lactose, is fermented using bacteria, it makes lactic acid. Lactic acid is what gives cheese its tangy flavor. Yogurt Like cheese, yogurt is made by fermenting the sugars in milk. One of the main microbes responsible is a bacteria called Lactobacillus (lak-toh-bah-SILL-us).

微型大厨 谁能想到微生物竟然也能在厨房帮大忙呢？ 几千年来，人类一直会在发酵过程中用到真菌和细菌。 这个过程能延长食物保质期，还能让食物更美味。 发酵 酵母是一种单细胞真菌。 它们通过发酵作用，把糖分转化成酒精、二氧化碳这类其他分子。 这就是人们会用酵母制作葡萄酒这类饮品的原因。 1 酿酒的第一步，是碾碎大量葡萄。 过去人们都是光脚踩葡萄来完成这一步哦！ 2 葡萄的表皮本身就带有天然酵母。 碾碎葡萄后，酵母就会和葡萄内部的糖分混合在一起。 发酵过程也就从此开始了。 3 当酒精浓度过高，酵母无法存活，就会死去。 如果在酵母死亡前就装瓶，二氧化碳气泡会被封在瓶中，让葡萄酒变得气泡十足。 人气食物 不少你意想不到的食物都用到了发酵工艺。 一起来看看全球最受欢迎的几种发酵食物吧。 面包 往面包面团中加入酵母，就会产生二氧化碳气泡。 气泡被困在面团里，才让面包变得松软蓬松。 面包里的小孔，就是二氧化碳气体留下的。 韩式泡菜 泡菜是韩国传统小菜，用大白菜和其他蔬菜制作而成。 细菌发酵白菜，让泡菜拥有了酸酸的口感。 奶酪 牛奶中有一种糖叫做乳糖，用细菌发酵乳糖后，会产生乳酸。 正是乳酸赋予了奶酪爽口的独特风味。 酸奶 和奶酪一样，酸奶也是通过发酵牛奶中的糖分制成的。 负责发酵的主要微生物之一，是名为乳酸杆菌的细菌（发音：lak-toh-bah-SILL-us）

Zombie ants! We normally think of fungi growing on dead plants and animals. However, some can grow inside living creatures, and even change their behavior. One freaky fungus even turns ants into zombies. Mind control When the spores of a certain fungus, called Ophiocordyceps unilateralis, land on an ant, they spread through the ant's body. Before long, the fungus will completely take over the ant's mind and behavior. 1 Spores land Spores fall from a fungus and land on an ant. They use special chemicals called enzymes to break into the ant's body. 2 Fungus infects The fungus cells multiply and spread through the ant. They release more chemicals that change the ant's behavior. 3 Ant climbs The fungus forces the ant to climb up to the top of a plant and bite down hard. 4 Fungus sprouts Now anchored to the plant by its strong jaws, the ant dies. The fungus growing inside the ant bursts out in long stalks. Fungus stalks sprout from the ant's head. The balls of fungus at the end of the stalks, called sporangia, will burst, releasing lots and lots of spores. The ant stays anchored to the plant even after it dies. 5 Cycle continues The fungus releases more spores, which fall onto other unsuspecting ants below, making new zombie ants. FUNGUS FARMERS Not all fungi are bad for ants. In fact, leaf-cutting ants grow fungi like crops. They take pieces of leaves to their undergroud nests. When fungus grows on the leaves, the ants farm it and eat it.

僵尸蚂蚁！ 我们通常都认为真菌只生长在死亡的动植物身上。 但有些真菌能长在活的生物体内，甚至还能改变它们的行为。 有一种诡异的真菌甚至能把蚂蚁变成僵尸。 精神控制 有一种叫做单侧蛇形虫草（Ophiocordyceps unilateralis）的真菌，它的孢子落到蚂蚁身上后，就会扩散到蚂蚁全身。 用不了多久，真菌就会完全控制蚂蚁的思想和行为。 1 孢子落定 真菌的孢子飘落下来，落到了一只蚂蚁身上。 它们会用叫做酶的特殊化学物质破开蚂蚁身体，钻进去。 2 真菌感染 真菌细胞不断繁殖，扩散到蚂蚁全身。 它们释放更多化学物质，改变蚂蚁的行为。 3 蚂蚁攀爬 真菌会强迫蚂蚁爬到植物顶端，再狠狠咬下去固定住自己。 4 真菌长出 蚂蚁用大颚牢牢固定在植物上后，就会死去。 长在蚂蚁体内的真菌会长出长长的茎伸出来。 真菌的茎会从蚂蚁的头部钻出来。 茎末端的真菌团叫做孢子囊，孢子囊破裂后，会释放出成千上万的孢子。 哪怕蚂蚁已经死了，也会一直牢牢固定在植物上。 5 循环继续 真菌释放出更多孢子，孢子落到下方毫无防备的其他蚂蚁身上，制造出新的僵尸蚂蚁。 真菌农夫 并不是所有真菌都对蚂蚁有害。 实际上，切叶蚁还会像种庄稼一样培育真菌。 它们会把碎叶片运回地下的巢穴。 真菌在叶片上长出来后，蚂蚁会照料它们，再吃掉真菌

What are algae? Have you ever seen what looks like green slime growing on a lake or pond? That's probably algae! This microbe is known for its color—but not all algae are green. The variety of these amazing creatures may surprise you. Diatoms These are a type of algae called diatoms. Each diatom is made of only one cell. They have shells made of opal, which is a bit like glass, and they're covered in intricate ridges and holes. Some diatoms are circles, while others are triangles, squares, or stars. Diatoms are see-through, like pieces of glass. Zoochlorella and kelp Algae come in many different shapes and sizes, from single-celled microscopic creatures to giant multi-celled seaweed. Zoochlorella Each of these teeny green blobs is its own single-celled algae called zoochlorella. Zoochlorella only live inside other creatures. Kelp Kelp is a type of algae called seaweed. It is usually brown and grows underwater in giant forests. In and out The hard shell of a diatom is impermeable—nothing can flow through it. That's why it's covered in small holes. The holes let in nutrients and let out waste products.

藻类是什么？ 你有没有在湖泊或池塘里见过长得像绿黏糊一样的东西？ 那大概率就是藻类哦！ 这种微生物因颜色出名，但并不是所有藻类都是绿色的。 这种神奇生物的多样性，一定会让你大吃一惊。 硅藻 这一类藻类叫做硅藻。 每一个硅藻都只由单个细胞构成。 它们有蛋白石构成的外壳，蛋白石有点像玻璃，外壳上还布满精巧的脊纹和小孔。 有些硅藻是圆形的，还有些是三角形、方形或是星形的。 硅藻是透明的，就像一块块小玻璃。 小球藻和海带 藻类有各式各样的形状和大小，小到单细胞微生物，大到巨型多细胞海藻都有。 小球藻 每一团小小的绿色团块，都是独立的单细胞藻类，叫做小球藻。 小球藻只生活在其他生物体内。 海带 海带是海藻的一种，也属于藻类。 它通常是棕色的，会在水下长成大片的巨型海藻林。 进出通道 硅藻的硬壳是不渗透的，任何东西都没法直接穿过外壳。 所以它的外壳上才布满了小孔。 这些小孔能让营养物质进来，代谢废物排出去

Growing green All algae have the same energy source. Just like plants, algae get energy from the sun in a process called photosynthesis. During this process, they also take in carbon dioxide gas and use it to make oxygen. Algal bloom When the temperature, sunlight, and other conditions are just right, algae can take over a pond, a lake, or even a large area of the ocean. These big, green bodies are called algal blooms, and they're quite a sight. Look closer These freshwater algae are green because of special molecules inside them called chlorophyll. The chlorophyll helps with photosynthesis. Algae are like the trees and grass of our oceans, lakes, ponds, and rivers. Like plants, they take in sunlight and use it to make sugar and oxygen. About half of the oxygen we breathe is made by algae! Energy from the sun The chlorophyll molecules inside algae take in energy from the sun and store it as sugar. Algae can use the sugar to move and grow. Some animals, such as this snail, eat algae, They want to use the high-energy sugar to move and grow, too!

生长变绿 所有藻类拥有相同的能量来源。 和植物一样，藻类通过光合作用这一过程从阳光中获取能量。 在这个过程中，它们还会吸收二氧化碳，并用它制造氧气。 藻类水华 当温度、光照和其他条件都适宜时，藻类会占领整片池塘、湖泊，甚至一大片海洋。 这些大面积的绿色聚集物就是藻类水华，景象十分壮观。 凑近看看 这些淡水藻呈绿色，是因为体内含有一种叫做叶绿素的特殊分子。 叶绿素可以辅助光合作用进行。 藻类就像海洋、湖泊、池塘和河流中的树木与青草。 和植物一样，它们吸收阳光，将光能转化为糖分和氧气。 我们呼吸的氧气里，大约有一半都是藻类制造的！ 来自太阳的能量 藻类体内的叶绿素分子吸收阳光的能量，将其储存为糖分。 藻类可以利用这些糖分运动和生长。 有些动物，比如这只蜗牛，会吃藻类，它们也想利用这些高能量糖分来运动和生长！

What are protozoa? Protozoa are made of one cell each, like bacteria, but they are actually more closely related to plants and animals. They behave like animals, too, by moving around and eating other living things. Amoeba An amoeba is a type of protozoa that looks like a splotch of jelly and can change shape constantly. It moves and eats by sending out leg-like limbs. Some amoebas prey on and eat other simple organisms, such as bacteria. 1 The amoeba sends out limbs to completely surround a bacteria. 2 These little sacks of enzymes, called lysosomes, move into attack position. 3 Once the bacteria is fully captured, the lysosomes release their enzymes. They break down the bacteria into nutrients, which are taken in by the amoeba as food. The cell membrane of an amoeba is very flexible and fluid. Cytoplasm makes up most of the inside of an amoeba. The amoeba's DNA is found in a central pouch called a nucleus. AMOEBAS Amoebas can sense chemicals given off by their food. This is like our sense of smell. THAT'S HUGE! Most creatures made of one cell are tiny, but not all. This amoeba is called a xenophyophore (zen-oh-FI-oh-fore). It's the biggest single-celled organism we know. It can grow up to 8 in (20 cm) across—bigger than your hand! Protozoa pals As well as amoebas, there are two other major types of protozoa. They are the ciliates and the flagellates. Ciliates Ciliates are covered in hair-like strands called cilia. They use them to move, eat, sense, and hold on to things. Flagellates Flagellates have at least one long tail, called a flagellum, that they use to swim. Some flagellates cause diseases in humans.

什么是原生生物？ 原生生物每个个体都只由一个细胞构成，这点和细菌类似，但实际上它们和动植物的亲缘关系更近。 它们的行为也和动物很像：会四处活动，还会捕食其他生物。 变形虫 变形虫是原生生物的一种，看起来就像一团果冻，还能不断改变形状。 它依靠伸出腿状的伪足来移动和进食。 有些变形虫会捕食其他简单生物，比如细菌。 1 变形虫伸出伪足，把细菌完全包裹起来。 2 这些装满酶的小囊叫做溶酶体，它们移动到了进攻位置。 3 当细菌被完全困住后，溶酶体就会释放出自身的酶。 酶会把细菌分解成养分，被变形虫吸收当作食物。 变形虫的细胞膜非常柔韧，具有流动性。 变形虫体内大部分物质都是细胞质。 变形虫的DNA储存在中心的囊状结构中，这个结构叫做细胞核。 变形虫的能力 变形虫可以感知到食物释放的化学物质。 这就相当于我们的嗅觉。 大得惊人！ 大多数单细胞生物都很微小，但并非全部如此。 这种变形虫叫做异生核虫（发音：zen-oh-FI-oh-fore）。 它是我们已知的最大单细胞生物。 它的直径能长到8英寸（20厘米）——比你的手掌还要大！ 原生生物类群 除了变形虫，原生生物还有另外两个主要类群。 它们就是纤毛虫和鞭毛虫。 纤毛虫 纤毛虫全身都覆盖着叫做纤毛的毛发细丝。 它们用纤毛来运动、进食、感知和附着。 鞭毛虫 鞭毛虫至少长有一根叫做鞭毛的长尾巴，用来游动。 有些鞭毛虫会让人类患上疾病。

What are archaea? Archaea also look a lot like bacteria, but their cell membranes are super strong. Archaea are known for being able to live in really extreme places where other microbes couldn't survive. Hot stuff Some archaea live in temperatures around 212°F (100°C)! They are called hyperthermophiles. High temperatures cause important molecules like DNA to break, so hyperthermophiles need to be really good at fixing broken molecules. The cell membrane of a hyperthermophile is strong to help it survive extreme heat, such as near an underwater vent. What is an underwater vent? Water seeps into cracks in the ocean floor where it's heated by hot rocks and magma. It then emerges in places called hydrothermal vents, which are like underwater volcanoes. Hyperthermophiles can be found living here. Archaea can have more than one flagellum, or tail, to help them move around. Where hot water from the vent meets cold water in the ocean, dark "smoke" forms. Hot water spews out the top of an underwater vent. Extreme archaea Archaea aren't only found living in high temperatures. Some archaea have made their home in other extreme environments. Surviving salt Scientists used to think nothing could survive in really salty water. However, some archaea can live in water that is 10 times saltier than the ocean. Resisting radiation Certain types of archaea can survive 3,000 times the exposure to a kind of energy, called radiation, that would kill a human. These creatures are truly tough. There are no diseases caused by archaea. MICROBE RAINBOW Not all extreme microbes are archaea. These beautiful rainbow colors circling the Grand Prismatic Spring at Yellowstone National Park in Wyoming are actually created by heat-loving bacteria.

什么是古菌？ 古菌看起来也很像细菌，但它们的细胞膜强度非常高。 古菌因能生活在其他微生物无法存活的极端环境而闻名。 热爱高温 有些古菌能在约212°F（100°C）的温度下生存！ 这类古菌叫做超嗜热菌。 高温会破坏DNA这类重要分子，所以超嗜热菌十分擅长修复受损的分子。 超嗜热菌的细胞膜十分坚固，帮助它们在水下热喷口附近这类极端高温环境存活。 什么是水下热喷口？ 海水渗入海床的裂缝，会被热岩石和岩浆加热。 之后受热的海水会从热液喷口涌出，这些喷口就像水下火山一样。 超嗜热菌就生活在这里。 古菌可以长有多根鞭毛（也就是尾巴），帮助它们移动。 当喷口喷出的热水遇到海洋里的冷水，就会形成黑色的“烟雾”。 热水从水下喷口的顶部喷涌而出。 极端古菌 古菌不单单生活在高温环境中。 有些古菌还定居在其他极端环境里。 高盐生存 科学家曾经认为，没有生物能在高浓度盐水中存活。 但有些古菌能生活在盐度是海水10倍的水域中。 抵抗辐射 某些古菌能承受的辐射量，是人类致死辐射量的3000倍。 这些生物真的非常顽强。 目前还没有发现古菌会引发任何疾病。 微生物彩虹 并非所有极端微生物都是古菌。 怀俄明州黄石国家公园大棱镜温泉周边环绕的美丽彩虹，其实就是喜热细菌形成的。