The Microbe World

What are Microbes?             |              Where Do Microbes Live?

Microbes are everywhere - a largely unseen world of living things that support life processes. "The Microbe World" provides a comprehensive directory of micro-organisms and their activities.
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The word protozoa means "little animal." They are so named because many species behave like tiny animals, they hunt other microbes as food.

Protozoa mainly feed on bacteria, but they also eat other protozoa,and sometimes fungi. Some protozoa absorb food through their cell tissues. Others,surround food and engulf it. Others have openings called mouth pores into which they sweep food. All protozoa digest their food in stomach-like compartments. As they digest, they make and give off nitrogen, which is an element that plants and other higher creatures can use.

Protozoa vary in size from 1/5,000 to 1/50 of an inch in diameter. They can be classified into three general groups based on their shape. One group is the Ciliates, which are generally the largest protozoa. They have hair-like projections called cilia and they eat the other two types of protozoa as well as bacteria. The second group is the Amoebae. The third group is the Flagellates, which are usually the smallest of the protozoa and have one or several long, whip-like projections called flagella extending from their cells.

To hunt, protozoa have to be able to move about. Amoebas ooze about by extending parts of their cells. Amoebae have fluid cell membranes or coverings that they can stretch out, bend and curve. As the membrane moves outward, the fluid and other parts inside the cell follow, flowing into the new bulge created by the moving membrane. Many Ciliates swim along by beating their cilia in a rhythmic pattern, like so many tiny oars. Flagellates swim by waving their flagella, using them much like a fish uses its tail to push itself through water.

Most protozoa do us no harm. But there are a few that cause diseases. One type of amoeba can live in human intestines. It feeds on red blood cells and causes a disease known as dysentery. Another species of protozoa can sicken hundreds of thousands of people when it gets into the tap water. Perhaps the best-known deadly protozoa causes malaria, a terrible disease that leads to about 800,000 deaths each year worldwide.

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