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BP: Fachverband Biologische Physik

BP 34: Imaging

BP 34.5: Vortrag

Donnerstag, 3. April 2014, 10:45–11:00, ZEU 250

Optical tweezers based coherent sub-diffraction 3D imaging of helical bacteria and sensing of deformation forces — •Matthias Koch, Julian Roth und Alexander Rohrbach — Lab for Bio- and Nano-Photonics, University of Freiburg, Georges-Koehler- Allee 102, 79110 Freiburg, Germany

Simple living cells such as bacteria are often regarded as model systems in order to analyse basic cellular reactions. The size of a bacterial cell or of small protrusions is often in the range of only a few tens to hundreds of nanometres and their shape may change rapidly. Therefore, advanced photonic measurement techniques are needed which are also capable of extracting forces and energetics on a broad temporal bandwidth. We show how an optical tweezers setup can be used to generate high contrast, 3D super-resolution movies of an only 200nm thin helical bacterium at rates up to 1kHz without any object staining [1]. Images are generated by analysing the interference pattern of the incident and the coherently scattered laser light in the back focal plane of a detection lens. Our system allows the simultaneous measurement and manipulation of fast shape changes and deformation forces generated by the cell. The bacterium itself uses a unique linear motor composed of cytoskeletal protein ribbons for propulsion/swimming. The subunits of these ribbons undergo subsequent conformational changes associated with force generation of the cell body. We show how this technique can be used to analyse the force an torque generation of the motor under different environmental situations.

[1] Koch, M. & A. Rohrbach (2012). Nature Photonics 6(10): 680-686