Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Japan.
FEBS Open Bio. 2021 Feb;11(2):404-412. doi: 10.1002/2211-5463.13051. Epub 2020 Dec 30.
Osmotic stress-induced injured cells of Escherichia coli were prepared by sorting live cells onto tryptic soy agar (TSA) containing 10-50% sucrose. The time course of colony-forming rate (CFR%) was analyzed. A time delay in colony formation indicated a sublethal effect. The final CFR level at 24 h indicated the relative number of culturable cells irrespective of injury. A value of (100-CFR)% at 24 h indicated a lethal effect. When cells were grown on TSA containing 10% sucrose, the time delay was 4 h and the lethal effect was 4%. However, dead cells inhibited the growth of live cells. Physical contact with insoluble matter derived from dead cells or dead cells themselves might have caused growth inhibition. These findings highlight a novel perspective on colony count methods in practical situations, such as when sampling foods containing a high concentration of sucrose.
通过将活细胞分选到含有 10-50%蔗糖的胰蛋白酶大豆琼脂（TSA）上，制备了渗透胁迫诱导的大肠杆菌损伤细胞。分析了集落形成率（CFR%）的时间进程。集落形成时间的延迟表明存在亚致死效应。24 小时时的最终 CFR 水平表示可培养细胞的相对数量，而与损伤无关。24 小时时的（100-CFR）%值表示致死效应。当细胞在含有 10%蔗糖的 TSA 上生长时，时间延迟为 4 小时，致死效应为 4%。然而，死亡细胞会抑制活细胞的生长。与来自死细胞或死细胞本身的不溶性物质的物理接触可能导致了生长抑制。这些发现为实际情况下的菌落计数方法提供了一个新的视角，例如在采样含有高浓度蔗糖的食物时。
