Leef J L, Mazur P
Appl Environ Microbiol. 1978 Jan;35(1):72-83. doi: 10.1128/aem.35.1.72-83.1978.
This study concerned the response to freezing of Neurospora crassa conidia in four different states: air-dry, hydrated in water, hydrated in Vogel medium lacking only sucrose, or hydrated in complete Vogel medium. All hydrated conidia were incubated in one of the above media for various times before freezing and were then washed and frozen in distilled water. Viability was estimated by three techniques, and the agreement among them was good. Hydration of air-dry conidia was found to be very rapid and, once hydrated, the conidia were much more sensitive to rapid freezing than they were before hydration. Rapidly cooled conidia survived freezing to a much higher extent when the warming rate was rapid than when it was slow; slowly cooled conidia showed little or no dependence on the warming rate. This sensitivity to rapid cooling and slow warming was attributed to the effects of intracellular ice. The sensitivity to freezing could be reversed by dehydrating the conidia in vacuo before freezing; thus, it was concluded that the presence or absence of water is the determining factor in the initial sensitivity due to freezing. In water, the sensitivity remained constant from 2 min to 15 days after hydration. Although conidia hydrated in growth medium lacking sucrose remained metabolically inactive, their sensitivity to rapid freezing decreased as a function of time in the medium before freezing. The reason for this decreased sensitivity is not understood. Conidia hydrated in complete growth medium (i.e., containing sucrose) became metabolically active and, after the initial sensitivity associated with hydration, became increasingly more sensitive to freezing as a function of their time in the medium. Drying itself was deleterious to metabolically active conidia, and those that survived dehydration did not exhibit a large absolute increase in resistance to subsequent freezing. The increase in sensitivity to freezing and to drying seems associated with the presence of metabolic activity; however, the precise cause of the sensitization remains obscure.
风干、在水中水化、在仅缺少蔗糖的Vogel培养基中水化或在完全Vogel培养基中水化。所有水化的分生孢子在冷冻前于上述培养基之一中孵育不同时间，然后洗涤并在蒸馏水中冷冻。通过三种技术评估活力，它们之间的一致性良好。发现风干的分生孢子水化非常迅速，一旦水化，分生孢子对快速冷冻的敏感性比水化前高得多。快速冷却的分生孢子在升温速率快时比升温速率慢时在冷冻后存活的程度要高得多；缓慢冷却的分生孢子对升温速率几乎没有或没有依赖性。这种对快速冷却和缓慢升温的敏感性归因于细胞内冰的影响。在冷冻前通过真空干燥分生孢子可以逆转对冷冻的敏感性；因此，得出结论，水的存在与否是冷冻引起初始敏感性的决定性因素。在水中，水化后2分钟至15天敏感性保持恒定。虽然在缺少蔗糖的生长培养基中水化的分生孢子仍保持代谢不活跃，但它们对快速冷冻的敏感性随着在冷冻前培养基中孵育时间的增加而降低。这种敏感性降低的原因尚不清楚。在完全生长培养基（即含有蔗糖）中水化的分生孢子变得代谢活跃，在与水化相关的初始敏感性之后，随着在培养基中时间的增加，对冷冻越来越敏感。干燥本身对代谢活跃的分生孢子有害，那些在脱水后存活下来的分生孢子对随后冷冻的抗性并没有大幅绝对增加。对冷冻和干燥敏感性的增加似乎与代谢活性的存在有关；然而，致敏的确切原因仍不清楚。
