The response exhibited by motile bacteria in a gradient of attractant or repellent. Bacterial movement involves straight runs and brief tumbles during which the direction of flagellar rotation reverses and the bacterium changes direction. If the concentration of an attractant is increasing, the probability of a tumble is reduced and the bacterium will persist up-gradient. The converse is true if the concentration is decreasing, and the net effect is to bias movement towards the source of the attractant. Purists would therefore consider this a klinokinesis with adaptation.
Subjects: Medicine and Health.