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Phototaxis is based on the principle that flagella guide bacteria to or away from some environmental stimulus. If the stimulus in question concerns nutrients, or other chemicals, then the process is called chemotaxis. However, there are some photosynthetic bacteria. Photosynthetic bacteria are not completely responsive to chemicals. Mainly, photosynthetic bacteria move toward light. This is called phototaxis.

Pho`to*tax"is (?), Pho"to*tax`y (?) , n. [NL. phototaxis; photo- + Gr. &?; an arranging.] (Biol.)

The influence of light on the movements of low organisms, as various infusorians, the zoöspores of certain algæ, etc.; also, the tendency to follow definite directions of motion or assume definite positions under such influence. If the migration is toward the source of light, it is termed positive phototaxis; if away from the light, negative phototaxis. -- Pho`to*tac"tic (#), a. -- Pho`to*tac"tic*al*ly, adv.


© Webster 1913

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