Thanks to Taro Gomi, we all know that everybody poops. Poop contains a lot of interesting stuff including tons of microbes, like bacteria. Depending on our own health, our poop can harbor both helpful and harmful microbes. And as a result, poop can spread disease.

So where do microbes in poop come from? Poop is a waste product formed in our intestines during digestion. Lots of different species of bacteria and other microscopic organisms like fungi and yeast live in our gut and they help our bodies break down food, make vitamins (like vitamin B and K), and fend off harmful bacteria. Some of  these microbes living in our gut actually get passed in our poop.

If we’re sick, our poop can also contain bacteria, viruses, and parasites that cause illnesses. In fact there are a lot of diseases that are spread in poop. For example, in the United States every now and then you may hear of E.coli outbreaks. E.coli is a type of bacteria that has lots of different varieties. Most are harmless and live in the gut of healthy people and animals and are passed in our poop. However, there are a couple of types of E.coli that can make people sick and cause diarrhea and vomiting if you ingest them. In the U.S. people sometimes get E.coli by eating undercooked beef that’s been contaminated by E.coli from the gut of cows, or from raw fruits or veggies contaminated by cattle poop from runoff from cattle fields. If you get E.coli you could pass it to another person if you don’t properly wash your hands after going to the bathroom.

You can also get sick if poop contaminates drinking water. In the U.S. and other developed countries this doesn’t happen often because we have sewage treatment plants and water treatment processes set up to make sure our drinking water is clean and free of harmful microbes. However, many places throughout the world, particularly developing countries, don’t have sewage and water treatment so it’s really easy for bacteria and other microbes from poop to contaminate drinking water. Some common diseases spread this way include cholera, typhoid fever, giardiasis, and rotavirus.

But poop isn’t all bad. In fact, doctors are starting to use healthy poop to treat some types of intestinal diseases, such as a condition known as C.diff colitis.  Check out this Gross Science video by our friends at NOVA that explains all about this.

This Science Spotlight video is part of our Engineering Is: Cleaning Poop from Drinking Water e-book. The e-book explores the science and engineering principles behind a device designed by scientists and engineers at Stanford University that purifies drinking water in Dhaka, Bangladesh. The e-book includes videos, interactives and media making opportunities. You can find all of our e-books at

Science Spotlight: The Good, the Bad and the Ugly of Poop 9 October,2015Lauren Farrar


Lauren Farrar

Lauren has a background in biology, education, and filmmaking. She has had the privilege to work on a diverse array of educational endeavors and is currently a producer for KQED Learning's YouTube series Above the Noise. Lauren's career has taken her to the deepest parts of the ocean to film deep sea hydrothermal vents for classroom webcasts, into the pool to film synchronized swimmers to teach about the pH scale, and on roller coasters to create a video about activation energy. And, she’s done it all for the sake of education. Lauren loves communicating science! Follow her on twitter @LFarrarAtWork

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