Ectoine is one of the most widely occurring of the 'compatible solute' organic osmolytes, used by many microorganisms to actively counteract the detrimental effects of water efflux across the semi-permeable cytoplasmic membrane on cell physiology. These compounds are fully congruous with metabolism and other cellular functions and so can be amassed to very high intracellular levels. A direct consequence of compatible solute accumulation is the raising of the osmotic potential of the cytoplasm, so allowing retention of water by the microbial cell and promoting water reentry.