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BP: Fachverband Biologische Physik

BP 32: Physics of Cells III

BP 32.13: Talk

Friday, March 30, 2012, 12:45–13:00, H 1028

(contribution withdrawn) Energy switching of helical bacteria trapped in a light tube — Matthias Koch and •Alexander Rohrbach — University of Freiburg, Georges-Koehler-Allee 102,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

A bacterium can undergo continuous transitions between ground states and excited states of mechanical energy. In the case of the wall-less - and therefore flexible - helical bacterium spiroplasma melliferum (SM), the deformations encode a state of mechanical energy storage, which can express a health state of the bacterium. SM has an extreme structural simplicity and is among the smallest cells in size (~500 genes, ~200nm thin, 3-5μm long). It infects various plants and insects and thereby has done 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 which molecular mechanisms work at which forces on which time scales?

We address these questions by optically caging the whole bacterium in an object adapted optical trap, which consists of a high speed scanning line optical trap: the light tube. Tiny phase changes from scattered laser light are recorded at several Kilohertz and allow imaging the whole bacterium at about 1000 Hz with 3D super-resolution. The measured dynamics is analysed and modelled with Fourier-techniques. We show experimental and simulation results, including energies and forces involved in its motility, as well as first models describing the switching of mechanical energy of the bacterium.