Lesson 2: Public Health Microbiology

Section II: Bacteria

2-6

[Previous] [Next]

Section II. BACTERIA

2-6. GENERAL

Bacteria are microscopic, unicellular organisms of the Kingdom Monera. They are widely distributed in nature, occurring nearly everywhere. They are found on and in our bodies, in the air we breathe, in the food we eat, and in the water we drink. They are part of the natural flora of the skin, naso-pharyngeal mucosa, and alimentary tract. They are particularly plentiful in the upper layers of the soil, playing an important part in the

decomposition of organic matter and in nitrogen fixation. There are several thousand known species of

bacteria; however, of this number, only about 100 species are pathogenic to man. Some also produce disease in the lower animals. The vast majority of bacteria, however, do not attack man or beast. They are not only harmless, but they are quite beneficial; without their help, all plant and animal life would cease. In this section, however, we are concerned with those bacteria that cause disease in man. Bacteria produce disease in man by invading the body and reproducing (colonizing), thereby causing damage to the host cells. Reproduction is by binary fission (paragraph 2-3e). Under favorable conditions, bacteria reproduce very rapidly. Some newly formed bacteria can mature and divide to form two new bacteria every 20 to 30 minutes. Most bacteria have independent metabolism, enabling them to live and multiply in a favorable medium outside of a host cell.

[Previous] [Next]