SURVIVAL OF BACTERIA UPON REPEATED FREEZING AND THAWING1

摘要: The following bacteria were employed as test organisms: Lactobacillus fermenti strain 69L-3, Escherichia coli 69L-15, and Serratia marcescens ATCC 274. They cultivated outlined previously (Major et al., 1955). Broth cultures of the organisms centrifuged, spent broth pipetted off, cells resuspended in a minimal amount fresh broth, then suspension diluted with additional to desired cell concentration. used suspending medium had percentage composition: yeast extract (B.B.L., dehydrated), 1.0; K2HP04, 0.2; MgSO4. 7H20, 0.01; "tween 80" (Atlas Powder Co.), 0.1. In some experiments L. contained 1 per cent trypticase dehydrated) 2 glucose ingredients. where water was from centrifuged culture an equal volume distilled again supernatant water, dispensed 5-ml aliquots into tubes (15 mm by 150 mm) fitted loosely aluminum caps. Freezing accomplished immersion alcohol bath at -22 C. After contents