The density difference between the cell body and the surrounding
medium causes sedimentation of the cell contents which results in
stretching the lower membrane and activates mechano-sensitive
ion channels in the membrane which changes the membrane potential
and finally triggers a reorientation of the flagellar movement
(Lebert et al., 1999). The impairment of graviorientation by
the addition of micromolar concentrations of specific inhibitors
of mechano-sensitive ion channels, such as gadolinium, shows that
the mechanism of mechano-sensitive ion channels is involved in
gravitaxis (Franco et al., 1991).