Viability of spores after repeated freezing and thawing shocks.
Survival of spores of the fungus Rhizopus nigricans after repeated freezing and thawing was investigated. The cooling rate was 10(4) degrees C/min. Dry spores were fully inactive after 32 repeated shocks. About one-half of spores were killed after 8 repetitions. The water content did not change the resistance, swollen spores reacted to shocks much like dry ones. The sensitivity of spores to freezing-thawing shocks increased considerably when the spores changed from the dormant to the active state. Already after a 30 min cultivation of spores in the nutrient medium two freezing and thawings were sufficient for inactivation of 60% spores. After a 90 min cultivation one freezing and one thawing were sufficient to inactivate practically all spores.
D003470:Culture Media; D005615:Freezing; D012233:Rhizopus / Q000254:growth & development / Q000502:physiology*; D013172:Spores, Fungal / Q000254:growth & development; D014867:Water
D003470:Culture Media; D014867:Water