Osmoregulation in Bacteria: Compatible Solute Accumulation and Osmosensing

Abstract

Environmental Context.Bacteria and Archaea have developed two basic mechanisms to cope with osmotic stress. The ‘salt-in-cytoplasm mechanism’ involves adjusting the salt concentration in the cytoplasm according to the environmental osmolarity and the ‘organic-osmolyte mechanism’ involves accumulating uncharged, highly water-soluble organic compounds in order to maintain an osmotic equilibrium with the surrounding medium. This highlight gives an overview of the osmoadaptation of prokaryotes employing the organic-osmolyte strategy and introduces a model explaining the fine-tuning of osmoregulatory osmolyte synthesis. Abstract.Bacteria and Archaea have developed two basic mechanisms to cope with osmotic stress, the salt-in-cytoplasm mechanism, and the organic-osmolyte mechanism. Organic osmolytes or so-called compatible solutes can be accumulated in molar concentration in the cytoplasm and allow for the adaptation of bacterial cells to varying salt concentrations. The biosynthetic pathways of compatible solutes and different compatible solute transport systems are described. A model for osmoregulatory compatible solute accumulation is introduced.