Nanomechanics measurements of live bacteria reveal a mechanism for bacterial cell protection: The polysaccharide capsule in Klebsiella is a responsive polymer hydrogel that adapts to osmotic stress

Abstract

A global health problem concerns the evolution of antibiotic-resistant bacteria. A characteristic of these super bug pathogens is their ability to form an exopolysaccharide matrix, the capsule, allowing them to resist antibiotic treatment and other environmental stresses. Here we apply atomic force microscopy (AFM) to interrogate living bacterial cells and provide the first in situ measurements of the biophysical behaviour of the capsule in physiologically relevant conditions. We prepared live Klebsiella pneumoniae, a common pathogen that has evolved super bug strains. We measured how capsule, cell wall and cell cytoplasm of wild type and capsule-deficient bacterial cells respond when indent..