Assembly of mechanosensitive channels can regulate whole cell volume

E.coli’s membrane embedded mechanosensitive channels (MSC) protect them from bursting when the intracellular osmotic pressure increases due to hyposmotic shock. MSC sense an increased membrane tension and respond by opening a large pore to passively let out cytoplasmic solutes. Using epifluorescence microscopy to look at single E.coli cells, we previously demonstrated that upon a hyposmotic shock cells rapidly swell due to water diffusion into the cytoplasm. Subsequently, MSC open to recover cell volume and osmotic pressure by solute efflux which lasted upto few minutes. Our phenomenological model explained the observed dynamics, however, could not capture large cell-to-cell variability. So, we propose a coarse-grained model which considers MSC dynamic aggregation and incorporate into the phenomenological model. Results suggests that MSC cluster at lower membrane tensions and disaggregate at higher membrane tensions, altering MSC’s opening probability, which also depended on tension. Additionally, we constructed a hepta-mutant (all 7 MSC genes deleted) and show that upon hyposmotic shock, the mutant swells but fails to recover cell volume; we illustrate the cells’ survivability and dynamics of death when they fail to restore internal pressure.