taxis (taxic response; tactic movement) The movement of a cell (e.g. a gamete) or a microorganism in response to an external stimulus. Certain microorganisms have a light-sensitive region that enables them to move towards or away from high light intensities (positive and negative phototaxis respectively). Many bacteria move in response to chemical stimuli (chemotaxis); a specific example is aerotaxis, in which atmospheric oxygen is the stimulus. Taxic responses are restricted to cells that possess cilia, flagella, or some other means of locomotion. The term is usually not applied to the movements of higher animals. See also geotaxis. Compare kinesis; tropism.

taxis (tactic movement) A change in direction of locomotion in a motile micro-organism or cell, made in response to certain types of external stimulus, e.g. the presence of particular chemicals (chemotaxis), changes in light intensity (phototaxis), or changes in temperature (thermotaxis), etc.

taxis A change in direction of locomotion in a motile micro-organism or cell, made in response to certain types of external stimulus (e.g. the presence of particular chemicals (chemotaxis), changes in light intensity (phototaxis), or changes in temperature (thermotaxis), etc.).

taxis (tak-sis) n. (in surgery) the returning to a normal position of displaced bones, organs, or other parts by manipulation only.

taxis The movement of an animal towards or away from a source of stimulation in response to the intensity and direction of the stimulus.