title: Dynamics of Escherichia coli's passive response to a sudden decrease in external osmolarity.
abstract: For most cells, a sudden decrease in external osmolarity results in fast water influx that can burst the cell. To survive, cells rely on the passive response of mechanosensitive channels, which open under increased membrane tension and allow the release of cytoplasmic solutes and water. Although the gating and the molecular structure of mechanosensitive channels found in Escherichia coli have been extensively studied, the overall dynamics of the whole cellular response remain poorly understood. Here, we characterize E. coli's passive response to a sudden hypoosmotic shock (downshock) on a single-cell level. We show that initial fast volume expansion is followed by a slow volume recovery that can end below the initial value. Similar response patterns were observed at downshocks of a wide range of magnitudes. Although wild-type cells adapted to osmotic downshocks and resumed growing, cells of a double-mutant ([Formula: see text]) strain expanded, but failed to fully recover, often lysing or not resuming growth at high osmotic downshocks. We propose a theoretical model to explain our observations by simulating mechanosensitive channels opening, and subsequent solute efflux and water flux. The model illustrates how solute efflux, driven by mechanical pressure and solute chemical potential, competes with water influx to reduce cellular osmotic pressure and allow volume recovery. Our work highlights the vital role of mechanosensation in bacterial survival.
authors.affiliation: Centre for Synthetic and Systems Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FF, United Kingdom.
authors.forename: Renata
authors.initials: R
authors.lastname: Buda
authors.affiliation: Biodynamic Optical Imaging Centre (BIOPIC), School of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Yunxiao
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Biodynamic Optical Imaging Centre (BIOPIC), School of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Yang
authors.affiliation: Centre for Synthetic and Systems Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FF, United Kingdom.
authors.forename: Smitha
authors.initials: S
authors.lastname: Hegde
authors.affiliation: Centre for Synthetic and Systems Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FF, United Kingdom.
authors.forename: Keiran
authors.initials: K
authors.lastname: Stevenson
authors.affiliation: Biodynamic Optical Imaging Centre (BIOPIC), School of Life Sciences, Peking University, Beijing 100871, China teuta.pilizota@ed.ac.uk fbai@pku.edu.cn.
authors.forename: Fan
authors.initials: F
authors.lastname: Bai
authors.affiliation: Centre for Synthetic and Systems Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FF, United Kingdom; teuta.pilizota@ed.ac.uk fbai@pku.edu.cn.
authors.forename: Teuta
authors.initials: T
authors.lastname: Pilizota
mesh_terms: D002463:Cell Membrane Permeability; D004926:Escherichia coli / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D008954:Models, Biological; D009994:Osmolar Concentration; D013997:Time Factors; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water
keywords: bacterial mechanosensing; osmotic downshock; single-cell imaging