Regensburg 2010 – scientific programme

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BP: Fachverband Biologische Physik

BP 32: Posters: Physics of Cells

BP 32.2: Poster

Thursday, March 25, 2010, 17:15–20:00, Poster B1

High-speed dynamics of helical bacteria trapped in a light tube. — •Matthias Koch and Alexander Rohrbach — University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

The helical bacterium spiroplasma melliferum is a wall-less bacterium, where genome reduction has left these bacteria with a minimal set of genes - sufficient for independent life and self-reproduction. As a consequence they have an extreme structural simplicity and are among the smallest cells in size (~200nm thin, 3-5μm long). However, they infect various plants and insects and thereby do tremendous harm to agriculture industry. Their motility, defined by helicity changes, kinking and propelling is very complex, and enables propagation in complex environments. However, it is unclear how this ~500 gene machine works. Which molecular motors and which filament proteins cooperate at which forces on which time scales? What are the energetic of this apparatus and how do they change during external disturbances. We try to answer these questions by optically trapping the whole bacterium in a light tube, which consists of a high speed scanning line optical trap. Although propelling and kinking, the bacterium remains in the focal plane and can thereby be observed with video microscopy. In addition, trapping light scattered at the slopes of the helix gives precise 3D information about its dynamics, which is analyzed and modelled with Fourier-techniques. We show experimental results, including energies and forces involved in motility, and compare them to simulation data. Further, we present a first model of how this minimal machine could work and which amount of power it needs for self-propulsion.