PUBLIC HEALTH MICROBIOLOGY
SECTION I. INTRODUCTION
a. Microbiology. Microbiology is the study of microscopic forms of life
(microbes). It includes their identification, their occurrence in nature, their physiology
and reproduction, the role they play in nature and in industry, their relationship to one
another and to man, and the means of controlling their activities. Microorganisms are
tiny, simple forms of life that can be seen only through a light microscope or an electron
microscope. Some microbes are complete as single cells, whereas others are
multicellular. They include the following groups of organisms, each of which will be
discussed in one of the subsequent sections of this lesson:
Bacteria (plural of bacterium).
Viruses (plural of virus).
Fungi (plural of fungus).
Protozoa (plural of protozoan).
b. Importance of Microbes. The importance of microorganisms is little
appreciated by the average person in civilized society. We take for granted the many
tremendously important functions performed by microbes in both nature and industry.
The decomposition of organic matter-dead animals and plants-into simple inorganic
compounds that serve as nutrients for plant life is accomplished by microbes. The
action of microorganisms contributes to the clarification and purification of polluted
waters. In the food and beverage industries, microbes are harnessed in the production
of buttermilk, cheese, beer, wine, and other products. At the same time, they pose a
threat, in that certain type, if not controlled, have properties that lead to the destruction
of such products. Microbes also play a role in the drug, tobacco, oil, lumber, and
c. Pathogenic Organisms. Aside from the beneficial role played by microbes
in maintaining the life cycle in nature, some of them have harmful effects upon other
forms of life--plants, animals, and man. Of the billions of microorganisms existing in
nature, only a relatively few are pathogenic (that is, disease producing) to man.
However, it is with these relatively few pathogenic organisms that we are concerned in
public health microbiology.