title: Superresolution imaging of dynamic MreB filaments in B. subtilis--a multiple-motor-driven transport?
abstract: The cytoskeletal protein MreB is an essential component of the bacterial cell-shape generation system. Using a superresolution variant of total internal reflection microscopy with structured illumination, as well as three-dimensional stacks of deconvolved epifluorescence microscopy, we found that inside living Bacillus subtilis cells, MreB forms filamentous structures of variable lengths, typically not longer than 1 μm. These filaments move along their orientation and mainly perpendicular to the long bacterial axis, revealing a maximal velocity at an intermediate length and a decreasing velocity with increasing filament length. Filaments move along straight trajectories but can reverse or alter their direction of propagation. Based on our measurements, we provide a mechanistic model that is consistent with all observations. In this model, MreB filaments mechanically couple several motors that putatively synthesize the cell wall, whereas the filaments' traces mirror the trajectories of the motors. On the basis of our mechanistic model, we developed a mathematical model that can explain the nonlinear velocity length dependence. We deduce that the coupling of cell wall synthesis motors determines the MreB filament transport velocity, and the filament mechanically controls a concerted synthesis of parallel peptidoglycan strands to improve cell wall stability.
authors.affiliation: Laboratory for Bio- and Nano-Photonics, Department of Microsystems Engineering-IMTEK, University of Freiburg, Freiburg, Germany.
authors.forename: Philipp V
authors.initials: PV
authors.lastname: Olshausen
authors.forename: Hervé Joël
authors.initials: HJ
authors.lastname: Defeu Soufo
authors.forename: Kai
authors.initials: K
authors.lastname: Wicker
authors.forename: Rainer
authors.initials: R
authors.lastname: Heintzmann
authors.forename: Peter L
authors.initials: PL
authors.lastname: Graumann
authors.forename: Alexander
authors.initials: A
authors.lastname: Rohrbach
mesh_terms: D001412:Bacillus subtilis / Q000166:cytology / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D057054:Molecular Imaging; D020409:Molecular Motor Proteins / Q000378:metabolism*; D021381:Protein Transport
chemical_list: D001426:Bacterial Proteins; D020409:Molecular Motor Proteins