Viruses and Bacteria Made Simple

Our world contains many organisms and things on-the-edge of life. They range in sizes so small that a light microscope cannot see them to organisms larger than an elephant. Bacteria and viruses are two examples of these very small earth inhabitants. Both are related in that both can cause sickness, and they both have genetic material. These two things differ in a few important ways.

Viruses are much smaller than bacteria. Bacteria can be seen under a light microscope when stained with special stains. Until the electron microscope was invented, viruses could not be seen at all. An electron microscope can magnify objects up to 10,000,000 times, which enables scientists to see objects that are beyond tiny.

Bacteria are a living organism, while viruses are not. Last week, we reviewed the characteristics needed for something to be considered alive. These characteristics include cells, reproduction, and metabolism. Bacteria are single-celled organisms that reproduce through a process called binary fission--the bacteria cell splits into two identical cells. Viruses are not made of cells, but consist of a core of genetic material surrounded by a protein shell.

Unlike most bacteria, viruses are not complete cells that can function on their own. A single virus particle in itself is essentially inert. It lacks the general components needed to reproduce. It must first infect a host cell, and then the host cell reproduces with the virus inside. Viruses cannot convert carbohydrates to energy, the way other living cells do. Viruses depend on other organisms for energy.

There are thousands of different viruses, and they can cause a wide range of disease. In humans, for instance, rhinoviruses cause colds, influenza viruses cause the flu, and herpes viruses cause cold sores and chicken pox among other things. Viruses can cause a range of conditions--from colds to measles to AIDS.

Most viruses do not cause serious disease and are killed by the body’s immune system. In many cases, you may never even know you had a virus. Unlike bacteria, which can be killed by antibiotics (how will be seen next week), most viruses are not effected by existing medicines. On a good note, scientists have been able to develop vaccines to combat against certain viruses. Many medicines can help alleviate the symptoms of a viral infection. Cough syrup is one example.

There are many differences between viruses and bacteria. Many of these differences stem from the fact that viruses are not a living thing, while bacteria are. Both cause sickness. Viruses cannot usually be treated, but the symptoms can. Bacteria can be treated with antibiotics. Next week, we will look at how antibiotics work.