The human body is a highly complex, multicellular life form whose structure and function depends on the coordinated interaction of roughly 10 trillion individual cells. On a microscopic level, the average human also carries a similar number of nonhuman visitors living opportunistically on and within the body. Freshly scrubbed and brushed, therefore, your body may outwardly appear clean and wholesome, but it is anything but sterile.
Your body is the mobile, warm-blooded equivalent of an ocean's coral reef, supporting a vast and highly divergent range of life. These microbes stretch from head to toe, spread across your skin, hide in the crevices of your mouth and nose, and follow your food from start to finish. Their presence is not just normal, but helpful or even necessary.
The life-style of these microorganisms is often described as a commensal relationship, in which they are tolerated by or even offer certain benefits to their host. For example, microbes are commonly found within the human intestinal tract, where they help to digest some foods and produce essential nutrients such as vitamins B12, K, thiamin, riboflavin, and pyroxidine.
Environmental Biology for Engineers and Scientists, by David A. Vaccari, Peter F. Strom, and James E. Alleman Copyright © 2006 John Wiley & Sons, Inc.
Perhaps even more important, the skin's normal biota actually offers a protective effect known as colonization resistance, which effectively safeguards the body against a hostile takeover by pathogenic (disease-causing) microbes. This effect can readily be appreciated during those periods when broad-spectrum antibiotics are used to combat a disease. The associated stress imposed on a body's normal biota can then lead to invasion by opportunistic, abnormal microbes (e.g., excessive growths of fungi such as Candida), which may lead to secondary health problems.
The composition of the human-associated microbial community will vary to some extent from one person to the next, and to some degree may also change with time. However, Table 12.1 provides a basic overview of the common locations and examples of the makeup of this normal microbial biota.
Was this article helpful?