Biology and You

You, Bacteria, and Viruses

Do good bacteria exist?

Yes, plenty of good bacteria are in and on the human body. For example, one type of bacteria helps you digest your food in the digestive tract and even helps you synthesize certain vitamins; another type barricades your skin from disease-causing bacteria; there are even bacteria on your tongue that help you protect the inside of your mouth. In fact, it’s estimated that one hundred trillion good bacteria live in or on the human body at one time. And these small creatures are prolific—it’s thought that we are actually only 10 percent human because every human cell that is necessary for our body comes with about ten “resident” microbes. These are called commensals, or generally harmless “freeloaders,” on and in our bodies; the mutualists, or doing us a favor as long as we don’t eliminate them; and in small numbers, pathogens that can harm us.


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