Copyright ยฉ 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Using the Metric System to Express the Sizes of Microorganisms Metric units are used to express the sizes of microbes. The basic unit of length in the metric system is the meter (m); it is equivalent to 39.4 inches. The sizes of bacteria and protozoa are usually expressed in terms of micrometers (ยตm). A micrometer is one millionth of a meter. A typical spherical bacterium (coccus) is approximately 1 ยตm in diameter. A typical rod-shaped bacterium (bacillus) is approximately 1 ยตm wide by 3 ยตm long.
















