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Bacteria vs. Viruses: How Are They Different?


There are fundamental differences between viruses and bacteria. Both of them, we call “microbes” or “germs,” but they look almost nothing alike.

Bacteria are alive in the same way that the cells that make up our own body are. Antibiotics are drugs that can kill bacteria, but not viruses.

Viruses, on the other hand, can barely be called alive at all. Viruses are simply small pieces of genetic material wrapped in a shell of fat and proteins. Most viruses are tiny compared to bacteria. A single particle of SARS-CoV-2, the virus that causes COVID-19, has a diameter of about 125 nanometers. Bacterium particles are much bigger, ranging between 400 and 3000 nanometers.

Bacteria can survive and grow on their own in most places on earth. Viruses are parasites that can’t do anything on their own outside of a living host. They are like tiny machines with no energy to run or replicate.

Viruses are inanimate “code” until they come alive inside a host. That host could be a human, animal, or even a bacteria. In fact, viruses that can infect bacteria have driven the evolution of both bacterial and human life.

SARS-CoV-2, a tiny virus with barely 10 genes (compared to the 20,000 genes found in human DNA), has transformed our world. It has laid bare the strengths and weaknesses of our science and brought into sharp focus many shortcomings of our social systems.

How could something so small do that?
Our bodies are brimming with bacteria that have adapted to viruses that infect bacteria. Many of these adaptations have helped us. For example, viruses help our guts maintain a diverse community of bacteria. We actually can’t live healthy lives without them!

Other virus-bacteria interactions in our bodies may harm us by allowing bad bacteria to go undetected by our immune systems.

Special thanks to Dr. Gary King in LSU’s Department of Biological Sciences. Dr. King’s work studies the distribution, diversity and activity of microbes that interact with trace gases in the Earth’s atmosphere with a focus on bacterial colonies in volcanic systems.