The Physics
Factbook
An encyclopedia of scientific essays

# Diameter of a Bacterium

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Microbiology, An Introduction. California: Tortura, Funke, Case, 1998. "Most bacteria range from 0.2–2.0 µm (micrometers) in diameter." 0.2–2.0 µm
Encarta Encyclopedia. Microsoft Corporation, 2000. "Less than 1 micron (0.001 mm/0.00004 inch) in length. Hundreds of thousands of bacteria can fit into a space the size of the period at the end of a sentence." > 1 µm
Alcamo, Edward. The Microbiology Coloring Book. New York: Addison Wesley, 1995. "Bacilli vary in size, and may be as long as 20 µm or as short as 0.5 µm.
Coccus = 0.5 µm, Spiral = 15 µm"
0.5–20 µm
Decelles, Paul. Cell size and geometry. Dr. Paul's Virtually Biology Show! "If you think about it for a bit you'll release [sic] that most cells are small: in fact too small to be seen by the unaided eye. The average cell in our body is about 50 micrometers(0.05 mm) in diameter. Indeed, if you were to average the diameter of all the cells on the planet, the average would certainly be far less than that because most of the cells on this planet are bacteria and the average bacterial cell is 3-5 micrometers in diameter." 3–5 µm

The word "bacterium"was probably used for the first time in the 1850s by Casimir Davaine who used the term to mean "rod"or "staff". There are three different basic forms of bacteria. Their role is normally related to diseases. There are the bacillus; which are rectangular with sharply rounded ends, which varies in diameter between 20 µm and 0.5 µm. The second type is a coccus; which resembles two tiny beans lying face to face. This type of bacteria is about 0.5 µm in diameter. The third kind is the spiral, which is about 15 µm in length.

Bacteria are both useful and harmful to humans. Some are used for soil enrichment with plants, in alcohol and cheese fermentation, to decompose organic wastes and clean up toxic waste sites, and in genetic engineering. Others, called pathogens, cause a number of plant and animal diseases including cholera, syphilis, typhoid fever and tetanus. Bacteria are so tiny that hundreds of thousands of them are able to fit into a space the size of the period at the end of a sentence.

The thousands of species of bacteria are differentiated by many factors, which includes morphology (the shape), chemical composition (usually detected by staining reactions), nutritional requirements, biochemical activities, and source of energy (sunlight or chemicals.)

Throughout all the sources I have found different average diameters, but it seems to be between 0.2 µm and 20 µm.

Joyce Wong -- 2001

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Faggart, Star. Biology: The Unity and Diversity of Life. 5th ed. California: 1989. "Prokaryote; no nucleus; 1–10 µm in size" 1–10 µm
"Bacteria." World Book Encyclopedia. Chicago: World Book, 1988: 19. "Most bacteria measure from 0.2–0.3 microns in diameter and can be seen only through a microscope (1 micron equals 0.001 millimeters)" 0.2–0.3 µm
"Bacteria." World Book Encyclopedia. Chicago: World Book, 1966: 17. "A single bacterium of a common type measures only 1/25,400 of an inch across." 0.965 µm
Todare, Kenneth. Major Groups of Prokaryotes. University of Wisconsin-Madison Department of Bacteriology (25 March 1998). "Mycoplasmas include the smallest known cells, usually about 0.2–0.3 micrometers in diameter." 0.2–0.3 µm
McGraw Hill Encyclopedia of Science and Technology, 8th ed. New York: McGraw Hill, 1997. "Extremely small usually 0.3–2.0 micrometers in diameter and relatively simple microorganisms passing the prokaryotic type of cell construction." 0.3–2.0 µm

Anthony Leto -- 1999

Bibliographic Entry Result
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Standardized
Result
Scientists Discover Biggest Bacteria Ever. CNN. (15 April 1999). "A team of German scientists studying sediment samples collected off the coast of Namibia say they have discovered the largest bacteria cell ever observed. The organism can grow to as large as 3/4 of a millimeter across, which means it is visible to the naked eye as a speck -- about the size of the period at the end of this sentence." 750 µm

Editor's Supplement -- 2006