In 1991, I became a professor of microbiology at the University of Texas Health Science Center in San Antonio. A microbiologist studies both good and bad germs. These germs can only be seen by a microscope, which makes little things appear bigger than they really are. Good germs are all around us, and many help us become healthier. Helpful germs make yogurt from milk, sauerkraut from cabbage, and wine from grapes.
Good germs can also help clean up our environment, like in oil spills.
Unfortunately, bad germs are also all around us, and make us sick. When you get scratched, you see that the skin turns red, and sometimes pus oozes out. This redness and pus are full of armies of cells and soldiers that have come to help you. The armies of cells, called platelets, come to destroy the germs and stop any bleeding. The soldiers belong to another army of cells and are called antibodies, which also come to kill the germs.