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BP: Fachverband Biologische Physik

BP 24: Physics of Cells II

BP 24.3: Talk

Thursday, March 17, 2011, 10:45–11:00, ZEU 250

High resolution imaging of the surface of single bacterial cells — •Dominik Greif, Daniel Wesner, Jan Regtmeier, and Dario Anselmetti — Experimental Biophysics & Applied Nanoscience, Bielefeld University, Universitaetsstr. 25, 33615 Bielefeld, Germany

Native surface structures of living bacteria are difficult to analyse by imaging with traditional scanning electron microscopy (SEM) because of possible artefacts that stem from the often necessary sample preparation procedures.

We systematically investigated the origin of surface morphology observed on Sinorhizobium meliloti bacterial cells by comparing results of the complementary techniques atomic force microscopy (AFM) and SEM. Those were applied from living bacteria in physiological environment to fixed bacteria in high vacuum. Stepwise, we applied different sample modifications (fixation, drying, metal coating, etc.) and characterized observed surface patterns. A detailed analysis revealed that the surface structure that is dominated by wrinkled protrusions in SEM images were not generated de novo but evolved from native structures on the surface of living bacteria [1]. In addition we evaluated the influence of osmotic stress to the surface morphology of living cells and also the contribution of exopolysaccharide and lipopolysaccharide (LPS) by imaging two mutant strains of the bacterium under native conditions [1]. Lastly, we could demonstrate that AFM images of living bacteria in culture medium allowed identification of surface features of the size of single proteins emphasizing the usefulness of AFM for high resolution cell imaging. [1] D. Greif et al., Ultramicroscopy 110 (2010) 1290-6