Maraccini P A, Wang D, McClary J S, Boehm A B
Department of Civil and Environmental Engineering, Environmental and Water Studies, Stanford, CA, USA.
J Appl Microbiol. 2015 May;118(5):1226-37. doi: 10.1111/jam.12773. Epub 2015 Mar 13.
To investigate how the growth stage of Enterococcus faecalis affects its photoinactivation in clear water.
Enterococcus faecalis were grown in batch cultures to four different growth stages or grown in chemostats set at four different dilution rates, then harvested and exposed to full spectrum or UVB-blocked simulated sunlight. Experiments were conducted in triplicate in clear water with no added sensitizers. Decay curves were shoulder-log linear and were generally not statistically different in experiments conducted under full spectrum light. Shoulders were longer and first order inactivation rates smaller when experiments were seeded with cells grown to stationary as compared to exponential phase, and for slower growing cells when experiments were done under UVB-blocked light. Chemostat-sourced bacteria generally showed less variability among replicates than batch-sourced cells.
The physiological state of cells and the method via which they are being generated may affect the photoinactivation experimental results.
Photoinactivation experiments conducted with exponential phase cells may overestimate the photoinactivation kinetics in the environment, particular if UVB-independent mechanisms predominate. Chemostat-sourced cells are likely to provide more consistent experimental results than batch-sourced cells.
研究粪肠球菌的生长阶段如何影响其在清水中的光灭活作用。
将粪肠球菌在分批培养中培养至四个不同的生长阶段，或在设定为四种不同稀释率的恒化器中培养，然后收获并暴露于全光谱或紫外线B（UVB）阻断的模拟阳光下。在不添加敏化剂的清水中进行了三次重复实验。衰减曲线呈肩-对数线性，在全光谱光下进行的实验中通常无统计学差异。与指数生长期相比，接种处于稳定期的细胞进行实验时，肩部更长且一级失活率更小；在紫外线B阻断光下进行实验时，对于生长较慢的细胞也是如此。来自恒化器的细菌在重复实验之间通常比来自分批培养的细胞表现出更小的变异性。
细胞的生理状态及其产生方式可能会影响光灭活实验结果。
用指数生长期细胞进行的光灭活实验可能会高估环境中的光灭活动力学，特别是在紫外线B非依赖机制占主导时。来自恒化器的细胞可能比分批培养的细胞提供更一致的实验结果。
