lab_08_motility - Miramar College Biology 205 Microbiology...

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Lab Exercise 8: Microbial Motility Page 1 of 3 Miramar College Biology 205 Microbiology Lab Exercise 8: Microbial Motility Background Many prokaryotes, single-celled eukaryotes and differentiated specialized cells of multicellular organisms ( e.g ., sperm cells) are capable of independent movement due to a special structure, the flagellum (plural: flagella ). Bacterial flagella are long, thin (~20 nm) structures that are usually not visible with the light microscope, except after staining with special flagellar stains which increase their diameter. The number and arrangement of flagella on a cell will vary among species and within a species when environmental conditions change. For instance, members of the genus Rhodospirillum will have a single polar or monotrichous flagellum in a liquid environment ( i.e . when grown in broth) but will increase the number of flagella on solid media to cover the entire body surface in a peritrichous arrangement . Additional flagellar arrangements include amphitrichous, where single flagella are located on opposite sides of the cell, and lophotrichous , where a tuft of flagella exists on one side of the cell. Although the physiological response to an environment that allows the bacterial cell to produce different flagellar arrangements is interesting, it will not be covered in this laboratory activity. Flagella allow cells to move toward (positive) or away from (negative) a stimulus in the environment, through a process known as taxis (plural: taxes ). If the stimulus is chemical, the process is referred to as chemotaxis . If the chemical is noxious, the bacterium will move away from it in a process called negative chemotaxis . Likewise if the chemical is beneficial the bacterium will move toward it in a process called positive chemotaxis . Similarly, bacteria are capable of
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This note was uploaded on 12/23/2009 for the course BIO 205 taught by Professor Murphy during the Fall '09 term at Miramar College.

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lab_08_motility - Miramar College Biology 205 Microbiology...

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