Genetic methods of detecting microorganisms reveal that the number of bacterial species in nature exceeds previous estimates by several orders of magnitude. In human mouths, for example, it is estimated that 500-700 microbial species are normally

Question

present. Explain why previous estimates were low.

What will be an ideal response?

Answer 1

Previous estimates of microbial diversity were largely based on the ability to detect microbes in samples handled in a typical laboratory setting. In most cases, laboratory conditions represent a narrow range of growth parameters, including temperature range, oxygen and other gas levels, and spectrum of nutrients. Even in cases where attempts are made to simulate the normal conditions for microbes (e.g., providing a high-pressure environment for organisms collected from a hyperbaric environment), microorganisms must frequently tolerate fluctuations in the growth environment or even exposure to extremely adverse conditions for short periods of time. Organisms that are intolerant of significant fluctuation in their environmental requirements do not survive transport to the lab to be measured or cultured. As a consequence, only the relatively few microbes that are versatile in their nutrient requirements and can tolerate fluctuations in their growth environment have been observed or isolated in the laboratory. This, in turn, resulted in misleadingly low estimates of microbial diversity.
Bloom's Taxonomy: Analysis
Section: Growth of Microbial Populations
Learning Outcome: 6.20