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Encompasses the Biological World

Microbes in the Environment

Microorganisms exist virtually everywhere in the biosphere (the thin envelope around the earth in which life exist). They are in our food, in water we use for drinking and bathing, on our utensils, on our clothing and bed sheets, and on our bodies. The air we breathe carries a wide variety of microbes. Their varied nature allows some types to survive in even the most unlikely environments. Microbes have been found in the thin cold air miles above the earth. Other microbes thrive in natural hot springs at a temperature of 90°C, and at least one type grows well at 105oC. Some bacteria can grow in sulfuric acid concentrated enough to kill virtually all type of other organisms. Other microbes proliferate in distilled or deionized water, using minute amounts of nutrients dissolved from the air.
Microorganisms inhabit the surfaces of living human and animal bodies and grow abundantly in the mouth and intestinal tract. There are ten times as many bacterial cells residing in your colon as there are human cells in your body. In fact one –third of the dry weight of human feces is bacteria. Yet mist persons are unaware of the presence of the trillions of microorganisms that inhabit their bodies because the microbes ordinarily stimulate no apparent physiological response and cause no disease. Such harmless microorganisms comprise the normal flora, those microorganisms that normally live on the human body in a harmonious relationship with their host.

It is far easier to identify the types of environments that are devoid of microorganisms because only a few such places naturally exist on earth. In the event of an erupting volcano, for example, all microbes would be incinerated. The interior of a healthy human body usually contains no microbes. (In the humans and other animals, interior does not include the digestive tract or outermost regions of the respiratory tract or outer most regions of the respiratory tract, which are extensions of the external environment). Your cerebrospinal fluid normally harbors no microorganisms. Similarly the blood and tissue fluids of a healthy person are microbe free, except for transient microorganisms introduced by trauma such as cutting the skin or accidentally biting the tongue. Urine in the bladder is also sterile, although it becomes contaminated with normal flora organisms during voiding. All the internal organs of a healthy person are free of microbial growth, thanks to a very effective complex of protective mechanisms that restrict microbes to the surface of the body and normally eliminated any cells that breach the surface. Because these protective mechanisms are internal to understand the relationship between microorganisms and humans, they are generally considered a part of the microbiology curriculum
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Microbes in the Environment

Microorganisms exist virtually everywhere in the biosphere (the thin envelope around the earth in which life exist). They are in our food,...