Elasticity of flagellar hooks

We have determined the magnitude of flexural rigidity of flagellar hooks of peritrichous and single polar flagellated bacteria. Several physical parameters, such as contour length and straight length, were measured from electron micrographs of curved flagellar hooks. We correlated the thermal bending motion of the flagellar hooks with their elastic properties and by employing the measured parameters we determined the elastic parameters of the flagellar hooks, such as bend persistence length and flexural rigidity. The extremely low magnitude of the flexural rigidity of the flagellar hooks clearly indicates that the flagellar hooks can flex easily in any desired direction. Interestingly, the flagellar hooks of single polar flagellated bacteria also possess an extremely low flexural rigidity. These results will help elucidate the role of flagellar hooks in the swimming process of single polar flagellated bacteria.