Gene

Physics

Cell wall

Biophysics

Salinity

Osmotic concentration

Cell

Osmosis

Osmotic shock

Chemistry

Ecology

Cytoplasm

Hydrostatic pressure

Membrane

Biochemistry

Osmoregulation

Cellular compartment

Biology

Turgor pressure

Cell biology

Osmotic pressure

Thermodynamics

Annual Review of Microbiology

The cytoplasm of bacterial cells is a highly crowded cellular compartment that possesses considerable osmotic potential. As a result, and owing to the semipermeable nature of the cytoplasmic membrane and the semielastic properties of the cell wall, osmotically driven water influx will generate turgor, a hydrostatic pressure considered critical for growth and viability. Both increases and decreases in the external osmolarity inevitably trigger water fluxes across the cytoplasmic membrane, thus impinging on the degree of cellular hydration, molecular crowding, magnitude of turgor, and cellular integrity. Here, we assess mechanisms that permit the perception of osmotic stress by bacterial cells and provide an overview of the systems that allow them to genetically and physiologically cope with this ubiquitous environmental cue. We highlight recent developments implicating the secondary messenger c-di-AMP in cellular adjustment to osmotic stress and the role of osmotic forces in the life of bacteria-assembled in biofilms.

Responses of Microorganisms to Osmotic Stress