Brad Parker, age 13, of Asbury Park, N.J., for his question:
WHAT IS BACTERIOLOGY?
Bacteriology is the study of single celled organisms called bacteria. Some kinds of bacteria cause serious diseases but other kinds are helpful.
A bacteriologist studies harmful bacteria to determine the exact way they cause disease so that better vaccines can be developed. They also study helpful bacteria to learn how to use and control them.
To establish that a certain type of bacterium causes a particular disease, a bacteriologist will follow four basic steps. These steps are called Koch's postulates, after the German physician, Robert Koch, who formulated them in the late 1800s.
Here are the steps: Pathologenic or disease causing bacteria are taken from diseased animals; the pathogenic bacteria are isolated and grown in a laboratory; the lab grown bacteria are injected into experimental animals; bacteria are isolated from the diseased experimental animals and shown to be the same kind as the original bacteria.
After a particular strain of bacteria has been isolated and grown, the bacteriologist places some of the bacteria on a glass slide and studies them under a microscope. He may also apply certain stains to the bacteria on the slide so they can be more easily seen.
If the bacteriologist wants to study the interior of a single bacterium, he may prepare a sample from a culture to study under an electron microscope.
Certain bacteria cause serious diseases because they produce powerful poisons. Vaccines to prevent some of these diseases can be prepared by growing the bacteria in a lab, isolating the toxins they produce and inactivating the toxins with heat or chemicals.
Most Americans are vaccinated against diptheria and tetanus with vaccines made by inactive toxins.
Bacteria were first seen by a Dutch merchant named Anton van Leeuwenhoek in 1676.
Bacteriology developed as a science during the late 1800s. The most famous bacteriologists of that time were Robert Koch and Louis Pasteur.
Pasteur, a French chemist, showed that bacteria caused fermentations or chemical changes, such as the souring of milk or the changing of wine into vinegar. He also identified the specific bacteria that cause certain kinds of fermentations.
Koch became the first scientist to show that specific bacteria cause certain diseases. He discovered that a rod shaped bacterium, Bacillus anthracis, causes anthrax in cattle and man. He also found that another rod shaped bacterium, Mycobacterium tuberculosis, causes tuberculosis.
The development of the electron microscope in the 1930s allowed bacteriologists to study the interior of bacterial cells.
Today, bacteriologists are still trying to learn more about how bacteria causes disease. They are also studying ways of using bacteria to help control water pollution and to treat sewage and industrial wastes.