Intracellular Water Exchange for Measuring the Dry Mass, Water Mass and Changes in Chemical Composition of Living Cells
a) In an H2O or D2O based fluid (1 or 3), the cell sinks as a result of the dry content’s density being higher than the surrounding fluid. In a dense impermeable fluid (2), the buoyancy of the cell’s water content dominates and the cell floats. b) The pairing of the different buoyant mass measurements allows the determination of different biophysical parameters of the cell as shown in the plot (not to scale). c) Kernel density estimates of probability densities for dry mass, water mass and total mass of a sample of fixed stationary-phase E. coli. Functions were rescaled so that their maxima were one. Solid bars represent sample medians.