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Microbial Organisms

roblem-causing microbial organisms (also known as microorganisms) include bacteria, fungi, algae, and viruses. It is often necessary to have the microorgan- ism identified in order to apply the appropriate control. However, their small size complicates identification. Proper identification usually requires the expertise of a specialist. Most of these organisms are so small that scientists must use powerful microscopes to see them. They may also carry out certain chemical tests to confirm their identity. For example, they may grow an organism in the laboratory or inject it into plants or laboratory animals so they can analyze the results for a positive identification. P

Usually, specific types of microorganisms are more prevalent in particular locations or under certain environmental conditions. Therefore, the location and environmental conditions of a site may aid in identification. In addition, fungi often produce unique structures such as molds or spore-producing bodies that can help to identify them. Some types of microorganisms are highly resistant to chemicals and many tolerate adverse environmental conditions, which contributes to the difficulty in controlling them.


Bacteria are microscopic, one-celled organisms. They reproduce in two different ways: by dividing to become two identical cells, a process known as fission, or by producing a spore that later develops into a new cell. Bacteria that form spores are difficult to control because spores are extremely resistant to heat, chemicals, and drying. Some bacteria can reproduce by fission as often as once every 15 to 30 minutes. Under ideal conditions, a single bacterium could become 70 billion bacteria in only 12 hours.

Scientists usually classify bacteria by their shape and the way they absorb special stains. Bacteria assume one of three shapes: spherical, rod-shaped, or spiral-shaped. If they turn a violet color when treated with a material called the Gram stain, they are “Gram-positive” bacteria. If they do not stain this color, they are “Gram-negative” bacteria.

Bacteria cause damage in one of two ways. Some produce toxins that are poi- sonous to other living organisms. These toxins may cause illness, paralysis, or death. Other bacteria produce enzymes that dissolve living cells or cause undesirable changes in nonliving materials such as adhesives and plastics. Sometimes these enzymes contaminate food or equipment or cause a buildup of material on surfaces of objects.



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