Katie Fullam, age 10, of Kezar Falls, Me., for her question:

WHAT ARE GERMS?

Any micro organism that can cause disease is commonly called a germ. The rather nonspecific term can actually apply to a number of disease producing creatures.

We often say that a person has picked up a germ, but the presence of these micro organisms wasn't known in early days. The modern basis of medical study, because of new knowledge in this important field, is sometimes referred to as the germ theory.

Included when we say ''germ'' are many types of  bacteria and viruses.

At least 500 different types of viruses have been discovered. They have been linked to a number of diseases including cancer. They are neither plant nor animal, but are forms of life that do not have a nucleus or a distinct cellular membrane as is true of all cells and other micro organisms.

Some scientists say that viruses were the first form of life on earth, and that they were formed out of the available organic chemicals. Just exactly how they came about and how other forms may have sprung from them may never be known, but scientific research certainly continues.

We know that today's viruses cannot live alone. They seek hosts to aid in their nutrition and reproduction. They spread by contamination. viruses may be sneezed or coughed into the air and can float about until breathed in or swallowed with food.

Bacteria are tiny, single celled plants which can reproduce by fission  that is, each cell can split in half to form two completely new organisms. They can be round or rod shaped and grow in clumps, chains, pairs or singly.

There are many kinds of'bacteria but only a few are dangerous to humans. The bad ones are known as pathogens, and they are responsible for such serious infections as tuberrculosis, diphtheria, typhoid fever, pneumonia and tetanus as well as leprosy, boils and scarlet fever.

,"he cocci type of bacteria causes over 90 percent of all skin infections. They are subdividing according to the arrangement and grouping of the bacterial cells. Those which form rows of cells resembling a chain are known as streptococci. When the cells stay in pairs after splitting, they are called diplococci; and  hen the cells remain in irregular masses resembling clusters of grapes, we call it staphylococcus.

The specialists in the field of biology who study microscopic life forms called bacteria are bacteriologists. Some may have Ph.D. degrees while others hold letters in medicine. In the ap lied bacteriology field, the doctor may work with disease prevention as a sanitary bacteriologist, or he may work as a pathological bacteriologist with bacteria that cause disease in man and animals.