Regensburg 2013 – scientific programme

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BP: Fachverband Biologische Physik

BP 13: Imaging

BP 13.4: Talk

Tuesday, March 12, 2013, 10:30–10:45, H44

Object-adapted optical trapping and shape-tracking of helical bacteria — •Matthias Koch and 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. Therefore, advanced photonic measurement techniques are needed which are also capable of extracting forces and energetics on a broad temporal bandwidth.

We show how the trapping potential of an optical tweezers setup can be adapted to the shape of a tiny elongated helical bacterium (Spiroplasma melliferum - SM) in order to hold and orient it in the focal plane of a microscope [1]. Further, the coherently scattered laser light is used to analyse its fast and complex cellular shape changes with nm precision at rates up to 1 kHz. By localizing each slope of the only 200nm thin bacterium we generate high contrast, super-resolution movies in three dimensions - without any object staining.

To demonstrate this method, we analysed SM bacteria and show how temporal changes in the transition between different energetic modes during external disturbances can be identified and imaged in 3D. As a response to an external perturbation, the minute long death of the bacterium is recorded and analysed by decaying energy fluctuations, which represents a novel approach in bacteriology.

[1] Koch, M. and A. Rohrbach (2012). "Object-adapted optical trapping and shape-tracking of energy-switching helical bacteria." Nature Photonics 6(10): 680-686.