Laboratoire de Physique Théorique
Toulouse - UMR 5152

By coupling the elastic properties of a rotative semi-flexible nanorod and hydrodynamic interactions, which are the source of propulsion in Stokes flows, a member of the Laboratory, in collaboration with German researchers, has shown theoretically that bacterial propulsion can be reproduced in a biomimetic way. Moreover, this work sheds light on the major role played by elasticity in flagellar motion of bacteria as E. coli.

Bacterial flagella of are helical stiff polymers set in motion at their base by a rotary motor. Using Brownian dynamics simulations with full hydrodynamic interactions which take into account momentum diffusion in Stokes flow, we show that a simple straight elastic nanorod which rotates around a point undergoes at a critical torque a strongly discontinuous shape bifurcation to a helical state. It thus gives rise to a substantial forward thrust regardless of its sense of rotation. Hence, in a biomimetic context, it makes usage of helical polymer unnecessary, allowing a selection from the much wider class of straight stiff polymers. Moreover, these elastic effects could explain some observations made on E. coli, such as the polymorphic transformations of their flagella.

The corresponding paper, Propulsion with a Rotating Elastic Nanorod has been published in Physical Review Letters, 96 068101 (2006). The corresponding author in the laboratory is Manoel Manghi.