Quite. Resistant little bastards, they can survive hard vacuum, dump them in space, and they can survive it. It is likely that their cellular composition consisting of a large amount of the sugar trehalose is responsible for this. Trehalose is primarily a fungal product, a disaccharide, first discovered in ergot of rye, (Claviceps purpurea) sclerotia, the overwintering structures formed after parasitic replication in grasses. Trehalose appears to function as a cryoprotectant, preserving cell architecture after freezing and allowing the cell to bounce back alive.