Machemer H, Nagel U, Bräucker R (1996) Gravitaxis in swimming cells: cell orientation distinguished from track orientation


Current understanding of the cellular graviresponses, gravitaxis as well as gravikinesis, implies a polar distribution of mechanically sensitive channels in the surface membrane of cells. A consequence of this organization is that both cell orientation and swimming speed are closely coupled to each other. These parameters are not easily measured, however, because the gravity-induced sedimentation rate generates an angular offset of the observed and digitally recorded swimming tracks from the orientation and velocity of the cells. We have developed a method, which identifies cell orientation from track orientation data using experimental determinations of the sedimentation rate. The isolation of the true cell orientation is most important in those cases, where cellular swimming was recorded under hypergravity conditions, and g-dependence of gravitaxis is being used as a tool for identification of the mechanisms of graviresponses.