Biophysical characterization of changes in amounts and activity of Escherichia coli cell and compartment water and turgor pressure in response to osmotic stress Export

@article{CayGutRec00, abstract = {To obtain turgor pressure, intracellular osmolalities, and cytoplasmic water activity of Escherichia coli as a function of osmolality of growth, we have quantified and analyzed amounts of cell, cytoplasmic, and periplasmic water as functions of osmolality of growth and osmolality of plasmolysis of nongrowing cells with NaCl. The effects are large; NaCl (plasmolysis) titrations of cells grown in minimal medium at 0.03 Osm reduce cytoplasmic and cell water to approximately 20\% and approximately 50\% of their original values, and increase periplasmic water by approximately 300\%. Independent analysis of amounts of cytoplasmic and cell water demonstrate that turgor pressure decreases with increasing osmolality of growth, from approximately 3.1 atm at 0.03 Osm to approximately 1.5 at 0.1 Osm and to less than 0.5 atm above 0.5 Osm. Analysis of periplasmic membrane-derived oligosaccharide (MDO) concentrations as a function of osmolality, calculated from literature analytical data and measured periplasmic volumes, provides independent evidence that turgor pressure decreases with increasing osmolality, and verifies that cytoplasmic and periplasmic osmolalities are equal. We propose that MDO play a key role in periplasmic volume regulation at low-to-moderate osmolality. At high growth osmolalities, where only a small amount of cytoplasmic water is observed, the small turgor pressure of E. coli demonstrates that cytoplasmic water activity is only slightly less than extracellular water activity. From these findings, we deduce that the activity of cytoplasmic water exceeds its mole fraction at high osmolality, and, therefore, conclude that the activity coefficient of cytoplasmic water increases with increasing growth osmolality and exceeds unity at high osmolality, presumably as a consequence of macromolecular crowding. These novel findings are significant for thermodynamic analyses of effects of changes in growth osmolality on biopolymer processes in general and osmoregulatory processes in particular in the E. coli cytoplasm.}, author = {Cayley, D. S. and Guttman, H. J. and Record, M. T.}, citeulike-article-id = {1700472}, journal = {Biophys J}, keywords = {10733957, biological, biophysics, cell, coli, compartmentation, concentration, cytoplasm, escherichia, govt, hypertonic, hypotonic, membrane, models, oligosaccharides, osmolar, osmotic, phs, pressure, research, solutions, support, us, water}, month = {Apr}, number = {4}, pages = {1748--1764}, pdf = {CayGutRec00.pdf}, posted-at = {2007-09-27 15:19:42}, priority = {2}, title = {Biophysical characterization of changes in amounts and activity of \emph{{E}scherichia coli} cell and compartment water and turgor pressure in response to osmotic stress}, volume = {78}, year = {2000} }

TY - JOUR ID - CayGutRec00 L3 - citeulike-article-id:1700472 N2 - To obtain turgor pressure, intracellular osmolalities, and cytoplasmic water activity of Escherichia coli as a function of osmolality of growth, we have quantified and analyzed amounts of cell, cytoplasmic, and periplasmic water as functions of osmolality of growth and osmolality of plasmolysis of nongrowing cells with NaCl. The effects are large; NaCl (plasmolysis) titrations of cells grown in minimal medium at 0.03 Osm reduce cytoplasmic and cell water to approximately 20\% and approximately 50\% of their original values, and increase periplasmic water by approximately 300\%. Independent analysis of amounts of cytoplasmic and cell water demonstrate that turgor pressure decreases with increasing osmolality of growth, from approximately 3.1 atm at 0.03 Osm to approximately 1.5 at 0.1 Osm and to less than 0.5 atm above 0.5 Osm. Analysis of periplasmic membrane-derived oligosaccharide (MDO) concentrations as a function of osmolality, calculated from literature analytical data and measured periplasmic volumes, provides independent evidence that turgor pressure decreases with increasing osmolality, and verifies that cytoplasmic and periplasmic osmolalities are equal. We propose that MDO play a key role in periplasmic volume regulation at low-to-moderate osmolality. At high growth osmolalities, where only a small amount of cytoplasmic water is observed, the small turgor pressure of E. coli demonstrates that cytoplasmic water activity is only slightly less than extracellular water activity. From these findings, we deduce that the activity of cytoplasmic water exceeds its mole fraction at high osmolality, and, therefore, conclude that the activity coefficient of cytoplasmic water increases with increasing growth osmolality and exceeds unity at high osmolality, presumably as a consequence of macromolecular crowding. These novel findings are significant for thermodynamic analyses of effects of changes in growth osmolality on biopolymer processes in general and osmoregulatory processes in particular in the E. coli cytoplasm. IS - 4 JF - Biophys J EP - 1764 TI - Biophysical characterization of changes in amounts and activity of \emph{{E}scherichia coli} cell and compartment water and turgor pressure in response to osmotic stress VL - 78 SP - 1748 KW - 10733957 KW - biological KW - biophysics KW - cell KW - coli KW - compartmentation KW - concentration KW - cytoplasm KW - escherichia KW - govt KW - hypertonic KW - hypotonic KW - membrane KW - models KW - oligosaccharides KW - osmolar KW - osmotic KW - phs KW - pressure KW - research KW - solutions KW - support KW - us KW - water AU - Cayley, DS AU - Guttman, HJ AU - Record, MT PY - 2000/Apr// ER -