Nanomechanical Properties of Dead or Alive Single-Patterned Bacteria

Abstract

The main goal of this paper is to probe mechanical properties of living and dead bacteria via atomic force microscopy (AFM) indentation experimentations. Nevertheless, the prerequisite for bioAFM study is the adhesion of the biological sample on a surface. Although AFM has now been used in microbiology for 20 years, the immobilization of micro-organisms is still challenging. Immobilizing a single cell, without the need for chemical fixation has therefore constituted our second purpose. Highly ordered arrays of single living bacteria were generated over the millimeter scale by selective adsorption of bacteria onto micrometric chemical patterns. The chemically engineered template surfaces were prepared with a microcontact printing process, and different functionalizations of the patterns by incubation were investigated. Thanks to this original immobilization strategy, the Young moduli of the same cell were measured using force spectroscopy before and after heating (45 degrees C, 20 min). The cells with a damaged membrane (after heating) present a Young modulus twice as high as that of healthy bacteria.

Impact of nano titanium dioxide exposure on cellular structure of Anabaena variabilis and evidence of internalization

“…These values are in the range (0.01-0.5 N/m) of those reported in the existing literature and related to bacterial cells [31]. One possible explanation for the increase in cellular turgor pressure as a result of exposure to nTiO 2 can be inferred from a previous study by Cerf [33] based on heat-treated Gram-negative bacteria. Briefly, structural membrane changes may be explained by the mediation of ROS, which have the potential to modify protein structure [17], protein folding configuration, and periplasmic layer thickness at the cellular membrane level, which results in the collapse of membranes' layers.…”

Antibiotic-induced modifications of the stiffness of bacterial membranes

“…to indent it). The shape of each indentation curve is then used to calculate the mechanical properties of the sample (specifically the stiffness) (Cerf et al, 2009;Polyakov et al, 2011;Rossetto et al, 2007). The data analysis was performed in a fully automated fashion by using OpenFovea, a free data processing software that uses the Hertz model to reconstruct stiffness maps of the entire image .…”

Reduction of the Peptidoglycan Crosslinking Causes a Decrease in Stiffness of the Staphylococcus aureus Cell Envelope

“…AFM can be used not only to obtain topological information on the cell surface and the organization of the peptidoglycan (20,22,(24)(25)(26), but it is also a powerful tool for quantitative studies of physical properties of the surface, such as the elasticity of the bacterial cell wall (27)(28)(29)(30)(31)(32)(33)(34). To characterize the mechanical properties of the bacterial cell wall, either purified peptidoglycan or live, intact bacteria can be employed.…”