The complex physical nature of the bacterial intracellular environment remains largely unknown, and has relevance for key biochemical and biological processes of the cell. Although recent work has addressed the role of non-equilibrium sources of activity and crowding, the consequences of mechanical perturbations are relatively less explored. Here we use a microfabricated valve system to track both fluorescently labeled chromosomal loci and cytoplasmic particles in Escherichia coli cells shortly after applying a compressive force, observing the response on time scales that are too sudden to allow for biochemical response from the cell. Cytoplasmic diffusion slows markedly on compression but the exponent governing the growth of the ensemble-averaged mean-squared displacement of cytoplasmic particles is unaffected. In contrast, the corresponding exponent for DNA loci changes significantly. These results suggest that DNA elasticity and nucleoid organization play a more important role in loci subdiffusion than cytoplasmic viscoelasticity under such short time scales.
Bibliographical noteFunding Information:
This work was supported by HFSP (RGY0070/2014). Fabrication was performed in the Minnesota Nanofabrication Center, which receives partial support from the National Science Foundation through the National Nanotechnology Infrastructure Network. We thank Dr. Estelle Crozat-Brendon for assistance with the culturing of the CJW4617 strain and and Dr. Michal Wlodarski for discussions.