Quantitative Mechanical Property Mapping of bacteria with PeakForce QNM I

MICAELA BIANCHI; CAROLINA DIAZ,; ALEJANDRO MIÑAN; PATRICIA L. SCHILARDI; LIA PIETRASANTA

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Since its development, AFM has proven itself to be a tool of choice to image soft biological samples, especially with the emergence of different operation modes and force spectroscopy and the fact that it is one of the few microscopy techniques that allows observation of cells under near-physiological conditions. PeakForce QNM is a new mode developed that acquires and analyzes the individual force curves from each tap that occurs during the imaging process. The curves are then analyzed to obtain the properties of the sample (adhesion, elasticity, modulus, deformation, and dissipation) and the result is images that contain maps of material properties [1]. In this study, we analyzed the effect of different treatments on the mechanical properties of the cell membrane of two types of bacteria: Pseudomona aeruginosa (Gram -) and Staphylococcus aureus (Gram +). The microorganisms were subjected to different treatments: silver ions (Ag +) and antibiotics. Single cells topographic images and spatially resolved forced maps reveal local significant variations of elasticity and nanomechanical properties across the cell surface due to complex, anisotropic composition of their walls. Acknowledgements: CONICET, ANPCyT and UBA. M. B. has a fellowship from CONICET. 1 Pittenger, B. et al., Bruker Application Note #128 (2011).