MicrobiOLogy > Ask a Scientist About Microbes

ASK A SCIENTIST: Microbes – What Are Microbes?

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On screen text: What are microbes? —Isabel, age 8 

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SUSAN PERKINS: Microbes are organisms that are too small to be seen without using a microscope. So, they include things like bacteria; archaea; single-celled eukaryotes, which are cells that have a nucleus, like an amoeba or paramecium; and sometimes we call viruses microbes too.

ASK A SCIENTIST: Microbes – What Do Microbes Look Like?

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On screen text: What do microbes look like? Do they all have the same size, shape, and color? —Troy, age 8

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SUSAN PERKINS: Microbes come in a huge variety of shapes; everything from rods, to spheres, even corkscrew shapes. They're all about the same size, with some a little bigger than others and smaller than others. In terms of their color, they don't really have much of a color unless we apply a stain to them, which we sometimes do so we can see them under the microscope.

ASK A SCIENTIST: Microbes – Where Do Microbes Live?

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On screen text: Where do microbes live? —Alexander, age 7

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SUSAN PERKINS: Microbes live everywhere. There are microbes at the bottom of the ocean, way up in the atmosphere, microbes under the ice at the polar caps, and about a trillion of them live in and on your body-- like your skin, in your gut, on your teeth. Everywhere in your body you have microbes.

ASK A SCIENTIST: Microbes – Are Microbes Good or Bad?

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On screen text: Are microbes good or bad? —Arison, age 8

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SUSAN PERKINS: So, yes, there are some microbes that we would call bad. Those are the ones that can make us sick, and we sometimes call them pathogens or germs. But more often than not, it's just a matter of the microbes being in the wrong place. And most of the microorganisms that are in and on our body are actually good for us. We need them to help us digest our food, keep out the bad microorganisms, and help make our immune systems and our whole bodies healthy.

ASK A SCIENTIST: Microbes – Are Viruses Microbes?

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On screen text: Are viruses microbes? —Jojo, age 7

Scene change to woman sitting in front of a bookcase, with stuffed animals and plants, begins to speak.

SUSAN PERKINS: So, scientists don't really agree on whether or not viruses are microbes, and that's because technically, they're not living. Viruses are just little packages of genetic material. DNA or RNA that need to get inside another cell in order to make copies of themselves.

So, if you just have a virus off by itself, it can't do anything. So, if we say that they are microbes, yes, they're too small to be seen without a microscope, but they may not really be living things.

ASK A SCIENTIST: Microbes – How Many Microbes Are In a Body?

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On screen text: How many microbes are in a body? How many on earth? —Anastasia, Age 11

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SUSAN PERKINS: Our best estimate is that we have a trillion microbes in our body. That's more microbes in our bodies than there are stars in the entire Milky Way galaxy. As far as how many microbes are on the earth, we really don't have any idea. But one scientist has estimated that if we take all of the microbes that are on the entire planet and put them on one side of a giant scale, and put all the plants and animals on the other side, the microbes would weigh more.

ASK A SCIENTIST: Microbes – Do Cats and Dogs Have the Same Microbes As People?

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On screen text: Do cats and dogs have the same microbes as people? —Russell, age 9

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SUSAN PERKINS: Sometimes cats and dogs have their own microbes, especially if they're going outside and interacting with other animals. But one thing that we've learned recently is that dogs are especially good at transferring microbes around people that live in the same house. Cats don't do it, presumably because dogs are more snugly and spend more time with everybody in the family.

ASK A SCIENTIST: Microbes – Why Do You Have Microbes In Your Stomach?

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On screen text: Why do you have microbes in your stomach? What do they do? —Joshua, age 10

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SUSAN PERKINS: You actually don't have very many microbes in your stomach because of the acid that's there digesting your food. It's a really harsh place, so we don't see many microbes there. When you move into the small intestine, we get a few more microbes, but your large intestine is where all the microbial action takes place. There is where you have millions to trillions of microorganisms helping you digest foods, especially fibers, and getting the most out of the nutrients out of it.

ASK A SCIENTIST: Microbes – What Kind of Scientists Studies Microbes?

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On screen text: What kind of scientist studies microbes? —Olivia, age 10

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SUSAN PERKINS: A microbiologist is someone who studies organisms that you need a microscope to see them with. They are too small to be seen without a microscope. What I work on in my lab are malarial parasites, which are single-celled organisms that can infect the blood cells of other creatures.

ASK A SCIENTIST: Microbes – How Long Have Microbes Been On Earth?

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On screen text: How long have microbes been on Earth? —Lina, Age 12

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SUSAN PERKINS: The estimate is that we've had microbes on planet Earth for four billion years. And in fact, for three of the four billion years that there's been life on Earth it was entirely just microbes.