Intertwining of Cellular Osmotic Stress Handling Mechanisms and Heavy Metal Accumulation

Osmoregulation mechanisms are engaged in the detoxification and accumulation of heavy metals in plants, microalgae and other microorganisms. The present review paper analyzes osmotic resistance organisms and their heavy metal accumulation mechanisms closely related to osmoregulation. In prokaryotic and eukaryotic microorganisms, such as the green algae-like protist Euglena, osmotic and heavy metal stresses share similar cell responses and mechanisms. Likewise, some plants have developed specific mechanisms associated to water stress induced by salinity, flooding, or drought, which are also activated under heavy metal stress. Thus, synthesis of osmo-metabolites and strategies to maintain stable the intracellular water content under heavy metal exposure induce a state of apparent drought by blocking the water maintenance systems. Heavy metals affect the cellular redox state, triggering signaling pathways for intracellular water maintenance, which are mediated by the concentration of reactive oxygen species. Hence, cellular responses and mechanisms associated with osmotic stress, once fully elucidated, represent new opportunities to improve mechanistic strategies for bioremediation of heavy metal-polluted sites.