Cryobiology of Neurospora crassa. II. Alteration in freeze response of Neurospora crassa conidia by additives

Neurospora crassa conidia in aqueous suspensions were frozen and thawed in the presence of various agents. Colony counts with these treatments were compared with those of the following (a) unfrozen, agent-treated, (b) unfrozen water suspended, and (c) frozen, water suspended. It was found that dimethyl sulfoxide (0.5–20%) resulted in total protection against freeze damage. Glycerol and calcium chloride decreased survival as much as 90% with fast freeze. The latter agents have properties which should decrease the rate of outflow of cellular water during temperature lowering. The results are consistent with the proposal that intracellular ice crystal growth to membrane rupturing dimensions is the damaging freeze mechanism under these conditions.