远缘链球菌6715及其耐氟菌株适应性耐酸能力的比较研究

目的：探讨远缘链球菌6715（Streptococcus sobrinus 6715，以下简称S．6715）及其耐氟菌株的适应性耐酸能力。方法：在含有不同氟浓度的TSA上逐步诱导S．6715产生耐氟突变株（以下简称S．6715-FR）。通过测定在各种酸性pH值培养基中预酸化2h后，能否使S．6715及其耐氟突变株抵抗致死性pH杀伤而存活及存活率，来测定其适应性耐酸能力的有无及大小。结果：S．6715属强适应性耐酸能力类菌株，最大生存率9．98％出现在pH5．5预酸化组，其耐氟突变株S．6715-FR亦具有强适应性耐酸能力，最大生存率10．55％出现在pn值5．0预酸化组。结论：在亚致死性pH值中生长能引发远缘链球菌6715及其耐氟菌株的某些生理变化，产生适应性耐酸能力，抵抗酸性环境的杀伤。

Comparison of the Acid Adaptation between Streptococcus Sobrinus 6715 and Its Fluoride-resistant Strains

Objective:To determine the acid adaptation of Streptococcus sobrinus 6715 and its fluoride-resistant strains.Methods: Fluoride-resistant strains of Streptococcus sobrinus 6715 was induced by increasing the concentration of fluoride in the TSA step by step.Adaptation to acid tolerance was measured by the ability of mid-exponential-phased cell to survive a 2-hour exposure at killing pH.Results: Preliminary exposure of mid-exponential phase cells to a low,sub-lethal pH would enhance survival rate.The greatest viability(9.98%) of sobrinus 6715 appeared when cells were pre-acified at pH 5.5 and the greatest viability(10.55%) of fluoride-resistant strains of Streptococcus sorbrinus 6715 appeared when cells were pre-acified at pH 5.0.Conclution: Pre-acidification can trigger the introduction of some mechanisms to protect Streptococcus sobrinus 6715 and its fluoride-resistant strains from acid killing.