Poster . . 6 th Int. Workshop − Scanning Probe Microscopy in Life Sciences − 9 October 2007 in Berlin 1/3 www.spm-workshop.jpk.com P17 − Mechanical Properties of Single Microorganisms Investigated by AFM Force Spectroscopy and Microcompression in Liquid Environment J. Arfsten, I. Kampen, A. Kwade Institut für Partikeltechnik Technische Universität Braunschweig, Germany In industrial biotechnology microorganisms (bacteria, fungi and algae) are utilized to produce diverse substances (e.g. enzymes, food and animal feed additives, pharmaceutical agents). The optimization and intensification of biotechnological processes require an overall understanding of the biological system. Whereas relationships on molecular levels are extensively investigated the mechanical properties of microbial cells and their dependencies on potential influencing parameters are still a field of research with numerous unsolved questions. Furthermore, effects of the cell mechanical properties on applied issues (e.g. the cell disruption behavior) have not been studied comprehensively. In the past mechanical properties of microorganisms were mainly investigated by local or global methods. Whereas the AFM force spectroscopy was used to probe local mechanical properties of cells 1 the microcompression technique stresses the entire cell in a compressive manner 2 . Up to now both techniques were applied independently of each other. This work aims to improve the fundamental understanding of the mechanical behavior of microorganisms by employing local as well as global characterization techniques. The results of both methods are to be compared and correlated. Later on, the gained knowledge shall be transferred to an applied research issue, namely cell disruption. Industrially relevant model organisms which have been chosen for the investigations are Escherichia coli and the baker’s yeast Saccharomyces cerevisiae (Figure 1). Local mechanical measurements are carried out using AFM force spectroscopy. Recorded force curves on single immobilized cells are analyzed by a physical model of two springs in series, namely the cantilever and the microbial cell. Thus, a microbial force constant can be determined. Global loading of single cells is realized using a commercially available Figure 1: (A) Yeast cell trapped in a membrane pore, (B) E. coli cells immobilized on a Poly-L-Lysine modified glass slide A B