On twitching motility and its mechanism.

Previously published reports have established a correlation between twitching motility and the possession of polar fimbriae in all cases examined. Twitching motility was shown to be highly dependent on the availability of liquid at the agar surface. In the present paper experiments are reported that establish: 1) the dependence of twitching on the existence of a layer of liquid of a particular thickness, 2) the production of such a liquid layer surrounding areas of growing organisms, and 3) the affinity of twitching bacteria for the air-water interface. Reasoning from these facts, it is postulated that the demonstrated affinity for the air-water interface is conferred upon the cells by the polar fimbriae. It is also suggested how the movements might be generated.