Abstract
Deformation of rotating flagellum of single-flagellated bacteria is analysed. The force exerted on the moving flagellum in viscous fluid is estimated applying the resistive force theory based on Stokes flow. The torsional as well as the bending moments are obtained according to the Kirchhoff elastic rod model. The curvature and the torsion of the deformed flagellum are determined assuming isotropic elastic relation for the flagellum. The deformation of the flagellum is obtained calculating an extended type of the Frenet-Serret equation.