Créach Véronique, Baudoux Anne Claire, Bertru Georges, Rouzic Bertrand Le
UMR CNRS 6553, Université de Rennes 1, Avenue du Général Leclerc, 35042 Cedex, France.
J Microbiol Methods. 2003 Jan;52(1):19-28. doi: 10.1016/s0167-7012(02)00128-8.
During the last 10 years, the dye 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) has been used to determine the in situ number of "active" bacteria in different ecosystems. A part of this success is due to a simple protocol, which does not require sophisticated equipment. However, it has not been established whether the method determines viable cells, e.g. those capable of growth and cell division, as opposed to cells that are active in the sense of having some detectable metabolic activity. In this study, the number of CTC-positive cells through the growth stages of Escherichia coli was estimated and compared to counts of the total number of bacteria, the culturability (CFU counts) and respiratory activity (CO(2) evolution). There was a good correlation between the number of CTC-positive cells and the CFU count, regardless of the growth phase. However, CTC could still be reduced by a large part of the population during the first hours of stationary phase even if the bacteria were no longer releasing CO(2). Thus, the reduction of CTC is a good estimator for cell viability, rather than cell activity. Additionally, a review of the literature showed that there is presently no standardized protocol for using CTC, which makes difficult at present the comparison of active bacterial numbers in different samples from different sites.
在过去10年中，染料5-氰基-2,3-二甲基氯化四氮唑（CTC）已被用于测定不同生态系统中“活性”细菌的原位数量。该方法取得部分成功的原因在于其操作流程简单，无需复杂设备。然而，目前尚未确定该方法测定的是否为活细胞，即能够生长和进行细胞分裂的细胞，而非仅具有某些可检测代谢活性的活跃细胞。在本研究中，对大肠杆菌生长各阶段中CTC阳性细胞的数量进行了估算，并与细菌总数、可培养性（CFU计数）和呼吸活性（CO₂释放量）的计数结果进行了比较。无论处于哪个生长阶段，CTC阳性细胞的数量与CFU计数之间都存在良好的相关性。然而，即使细菌不再释放CO₂，在稳定期的最初几个小时内，仍有很大一部分细菌群体能够使CTC还原。因此，CTC的还原是细胞活力的良好指标，而非细胞活性的指标。此外，文献综述表明，目前尚无使用CTC的标准化方案，这使得目前难以比较来自不同地点的不同样品中活性细菌的数量。
