Mechanosensing refers to the ability of an organism to respond to changes in mechanical force on them or their environment. The mechanical stress can be in a variety of forms:
- Hydrostatic pressure, as in the case of deep ocean environments
- Fluid shear stress, as in the case of blood flowing through veins
- Direct force, as in the case of body weight on a bone
- Osmotic pressure, resulting from a difference in solute concentrations across a semi-permeable membrane
High hydrostatic pressure (HHP) can cause dissociation of multimeric proteins, shifts in reaction equilibria, decreased membrane fluidity, and even unfolding of monomeric proteins in extreme cases (reviewed in . In some cases, changes in mechanical stress result in differential gene expression driven by mechanosensitive promoters or repressors. Genes that have increased expression might include cold- and heat-shock and other stress response proteins, barostable synthases [vezzi ref?], or membrane proteins [add reference]. Down-regulated genes might include nutrient transporters [Mal operan ref]. In other cases, porin proteins which provide ion diffusion pathways are opened in response to osmotic stress across the membrane.
The first pressure-responsive gene was found in 1989  in a deep-ocean bacterium, Photobacterium profundum strain SS9. The gene encodes for OmpH, a large transmembrane protein which is involved in nutrient uptake. Later work found that the operon also contained two outer membrane proteins, OmpL [include ref] (induced at lower pressures ~1atm) and OmpI [include ref] (induced at much higher pressures ~400atm). These pressure inducible genes were found to be essential for survival under HHP growth conditions[include a ref].
- Morozkina EV, Slutskaia ES, Fedorova TV, Tugaĭ TI, Golubeva LI, and Koroleva OV. [Extremophilic microorganisms: biochemical adaptation and biotechnological application (review)]. Prikl Biokhim Mikrobiol. 2010 Jan-Feb;46(1):5-20.
- Bartlett D, Wright M, Yayanos AA, and Silverman M. Isolation of a gene regulated by hydrostatic pressure in a deep-sea bacterium. Nature. 1989 Nov 30;342(6249):572-4. DOI:10.1038/342572a0 |
First discovery of pressure-regulated gene