Dresden 2011 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 22: Physics of Cells I

BP 22.9: Vortrag

Mittwoch, 16. März 2011, 17:30–17:45, ZEU 250

(contribution withdrawn) Mechanical energetics of helical bacteria trapped in a light tube — Matthias Koch and •Alexander Rohrbach — University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

The wall-less, helical bacterium spiroplasma melliferum has an extreme structural simplicity and is 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. It has been hypothesized only recently that spiroplasms are responsible for mad cow disease and Creutzfeldt-Jakob-disease. 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 machines work 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 its 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.