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United States Department of Agriculture

Agricultural Research Service

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Tummy Trouble

Protozoa are tiny, one-celled creatures that can make a comfortable home out of any place with some moisture in it—the soil, ponds, air vents or even the insides of animals. Although they can only be seen by using microscopes, these little critters share a couple of characteristics with much larger mammals: They move about, and they breathe oxygen.

It's true that some of the many types of protozoa in the world can be harmful all by themselves. Photo: Microbiologists Mark Rasmussen and Sharon Franklin examine a culture of protozoa. But many others are helpful. Inside animals, one of the most important things protozoa do is gobble up bacteria that can cause disease.

So imagine the surprise of ARS scientists when they discovered that some protozoa inside cows can actually strengthen bacteria that cause nasty diseases. What's more, the protozoa help the bacteria fight off medicines designed to defeat the bacteria!

That's what researchers Mark Rasmussen and Steven Carlson found at the ARS National Animal Disease Center (NADC) in Ames, Iowa, when they studied protozoa that live in the first stomach—the rumen —of cows.

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Last Modified: 4/7/2008
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