On the `Listeria' propulsion mechanism

Three aspects of the investigation into the propulsion mechanism of the bacterium, listeria, are presented: mechanical properties of the comet of the native bacterium; the polymerization/crosslinking process of actin gels in a spherical geometry; and a theoretical analysis of the mesoscopic aspects of the propulsion. It is shown experimentally that the physical connection between the comet and the bacterium plus the existence of a well-defined gel modulus imply the build up of stresses which propel the bacterium. Studying the effect of topology on the polymerization dynamics provides experimental evidence for and evaluation of the stresses. A model which takes into account the observed phenotypes is presented.