Osmoprotectants or
compatible solutes are small molecules that act as
osmolytes and help organisms survive extreme
osmotic stress. In plants, their accumulation can increase survival under stress e.g. drought . Examples of compatible solutes include
betaines,
amino acids, and the sugar
trehalose. These molecules accumulate in cells and balance the osmotic difference between the cell's surroundings and the
cytosol. In extreme cases, such as in
bdelloid rotifers,
tardigrades,
brine shrimp, and
nematodes, these molecules can allow cells to survive being completely dried out and let them enter a state of suspended animation called
cryptobiosis. In this state the cytosol and osmoprotectants become a glass-like solid that helps stabilize
proteins and
cell membranes from the damaging effects of desiccation.