Table 1.

Glossary

TermDefinition
ChaotropeCosolvents that decrease water structure are called chaotropes. Urea and other protein denaturants are chaotropes.
ChemosensorChemosensors are molecules that detect specific ligands. Many chemosensors act by binding a specific ligand at a structure-specific receptor site.
Compatible soluteA compatible solute is a cytoplasmic cosolvent whose level can be modulated over a broad range without disrupting cellular functions.
CosolventA cosolvent is a solute that significantly affects the properties of water as a solvent, rendering the resulting solution nonideal.
DehydrationDehydration is water loss. (Desiccation is complete water removal.)
Hofmeister effectThe Hofmeister effect is the systematic effect of a series of inorganic salts on the solubility of proteins and was first reported by Franz Hofmeister in 1888. Many other solute effects have since been correlated with the Hofmeister effect, and it has been generalized to include both ionic and nonionic solutes. Solutes (or cosolvents) are categorized, according to the Hofmeister effect, as chaotropes or kosmotropes.
KosmotropeCosolvents that increase water structure are called kosmotropes. Glycerol, glycine betaine, and other protein stabilizers are kosmotropes.
OsmolalityOsmolality is the osmotic pressure of a solution at a particular temperature, expressed as moles of solute per kilogram of solvent (osmolal) (see appendix). Osmolality can be measured but not calculated.
OsmolarityOsmolarity is an approximation for osmolality, expressed as moles of solute per liter of solution (osmolar) (see appendix). Osmolarity is calculated as the sum of the concentrations of osmotically active solutes in a solution.
OsmoprotectantOsmoprotectants are compounds that stimulate bacterial growth in high-osmolality media.
Osmoregulatory response  An osmoregulatory response is a physiological process that mitigates passive adjustments in cell structure caused by changes in the extracellular osmolality.
OsmosensorAn osmosensor is a device that detects changes in extracellular water activity (direct osmosensing) or resulting changes in cell structure or composition (indirect osmosensing).
OsmotoleranceThe osmolality range for the media that support bacterial growth.
Osmotic downshiftAn osmotic downshift is a decrease (over time) in the osmolality of the extracellular environment.
Osmotic upshiftAn osmotic upshift is an increase (over time) in the osmolality of the extracellular environment.
Turgor pressureTurgor pressure (ΔP) is the hydrostatic pressure difference which balances the osmotic pressure (or osmolality) difference between cell interior and exterior. Turgor pressure renders the chemical potentials of intracellular and extracellular water equal at equilibrium.