The Movement of Listeria Monocytogenes
Although not the most important type of research I have come across, V. B. Shenoy*, D. T. Tambe*, A. Prasad, and J. A. Theriot has conducted work on the kinematics description of the trajectories of Listeria monocytogenes propelled by actin comet tails. In other words, which way does listeria monocytogenes spin around?
Yes that’s right, these researchers from the Division of Engineering, Brown University, Providence, RI 02912; Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; and Department of Biochemistry, Stanford University, Stanford, CA 94305 have made some ground breaking discovery. That Listeria monocytogenes move in a number of fascinating geometrical trajectories. Now if only I had some spare time I might do the same for salmonella.
Anyhow, here’s the abstract:
“The bacterial pathogen Listeria monocytogenes propels itself in the cytoplasm of the infected cells by forming a filamentous comet tail assembled by the polymerization of the cytoskeletal protein actin. Although a great deal is known about the molecular processes that lead to actin-based movement, most macro scale aspects of motion, including the nature of the trajectories traced out by the motile bacteria, are not well understood. Here, we present 2D trajectories of Listeria moving between a glass-slide and cover slip in a Xenopus frog egg extract motility assay. We observe that the bacteria move in a number of fascinating geometrical trajectories, including winding S curves, translating figure eights, small- and large-amplitude sine curves, serpentine shapes, circles, and a variety of spirals. We then develop a dynamic model that provides a unified description of these seemingly unrelated trajectories. A key ingredient of the model is a torque (not included in any microscopic models of which we are aware) that arises from the rotation of the propulsive force about the body axis of the bacterium. We show that a large variety of trajectories with a rich mathematical structure are obtained by varying the rate at which the propulsive force moves about the long axis. The trajectories of bacteria executing both steady and saltatory motion are found to be in excellent agreement with the predictions of our dynamic model. When the constraints that lead to planar motion are removed, our model predicts motion along regular helical trajectories, observed in recent experiments.”
