|Tortora, Funke, & Case. Microbiology: An Introduction. Redwood City, CA: Benjamin Cumming, 1995: 275.||"However, a bacterium can typically move about 100 times its body length in a second (or about 50 µm/sec), whereas a large fish such as tuna can move only about 10 times its body length in this time."||50 µm/s|
|"Bacteria." The World Book Encyclopedia. Chicago: Field Enterprises, 1973: 18.||"Many bacteria can swim as fast as 50 microns per second."||50 µm/s|
|Pleczar & Chan. Microbiology. 4th edition. New York: McGraw Hill, 1977: 86.||"It has been reported that the flagella of Spirillum serpens rotate at a rate of 2,400 r/min, while the body rotates at 800 r/min and the estimated forward speed of the cell is 50 µm/s. Vibrio comma, a polar flagellate, has been reported to move at a rate of 200 µm/s."||50 µm/s
|"Bacterial motility." McGraw-Hill Encyclopedia of Science and Technology. New York: McGraw Hill, 1960: 63.||
|Guinness Book of World Records. New York: Bantam. 1991: 128.||"The rod-shaped bacillus Bellovibrio bacteriovorus, by means of a polar flagellum rotating 100 times/sec., can move 50 times its own length of 2 µm per sec."||100 µm/s|
Bacteria are the smallest self-sustaining organisms. They can be found everywhere on earth and even at altitudes up to 41,000 m (135,000 ft). In contrast to other unicellular creatures, bacteria lack a nucleus, endoplasmic reticulum, mitochondria, and other organelles. Their basic structure is comprised of DNA and ribosomes suspended in cytoplasm. This is encased in a plasm membrane, cell membrane and capsule. There may be flagella and pilli extending from the cell wall. Unlike flagella, pilli do not aid in bacterial motility.
Approximately half of all bacteria known to man are motile. Most of these bacteria move with the aid of flagella, a long helical appendage composed of a protein called flagellin. Flagella are connected to the bacterium by a basal region and their rotation propels the cell forward. In polar bacteria, the flagella are located at the poles or ends. Monotrichous bacteria have one flagellum located at one pole. Amphitrichous bacteria have one flagellum at each pole. Two or more flagella at one or both poles are found on lophotrichous bacteria. Peritrichous bacteria have flagella all over their surface.
Atrichous bacteria have no flagella. They move by means of gliding (e.g., Beggiatoa) or they don't move at all (e.g., cocci). Gliding bacteria will move only when they are in contact with a solid plane. An example of gliding bacterium is Myxococcus. It decreases surface tension at its posterior end by secreting a substance known as surfactant. The difference in surface tension between the back and front of this bacterium causes it to glide.
Bacteria can reach speeds from 2 microns per second (Beggiatoa, a gliding bacteria) to 200 microns per second (Vibrio comma, polar bacteria). Speed varies with type of bacteria, but flagellates are undoubtedly faster than gliders.
Elaine Kung -- 2000