Nanoscale quantification of longitudinal and transverse mechanics of bacterial bodies

Abstract

Mechanical studies focused on flagella and pili of bacteria, typically estimated by evaluating bending persistence length measurements or Young's modulus, fail to consider the behavior of the whole bacterial body, which can undergo significant changes during antimicrobial resistance. In this Letter, we investigate the biophysical properties of an important plant bacterial pathogen, Xanthomonas perforans, the causal agent for bacterial spot disease of tomato and pepper. The emergence of copper-tolerant strains of X. perforans is predicted to have a devastating impact on industrial scale productions, making it essential to advance approaches to distinguish copper-tolerant from the copper-sensitive X. perforans strains. After introducing a means to measure the bending stiffness of bacteria using atomic force microscopy (AFM), we propose a comparison of the longitudinal and transverse mechanical properties by acquiring high resolution images and force curves of the bacteria. A quantification of the longitudinal and transverse Young's modulus of bacteria reveals significant differences between copper-sensitive and copper-tolerant strains of X. perforans. The present approach is expected to significantly advance the fundamental understanding of bacterial phenomena, such as by monitoring the therapeutic efficacy of newly developed materials on individual X. perforans in situ to relate them to the behavior of their colonies or biofilms.