ACID TOLERANCE, PROTON PERMEABILITIES, AND MEMBRANE ATPASES OF ORAL STREPTOCOCCI
ACID TOLERANCE, PROTON PERMEABILITIES, AND MEMBRANE ATPASES OF ORAL STREPTOCOCCI
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DOI：
10.1128/iai.53.2.331-338.1986
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发表时间：
1986-08-01
影响因子：
3.1
通讯作者：
MARQUIS, RE
中科院分区：
文献类型：
--
作者：
BENDER, GR;SUTTON, SVW;MARQUIS, RE
研究发现，代表性口腔链球菌的耐酸差异与细菌对质子的动态渗透性关系更密切，而与细胞膜对环境酸化造成的严重损害的敏感性差异关系更大。对于变形链球菌GS-5、血链球菌NCTC 10904和salvarius链球菌ATCC 13419，通过从整个细胞中释放镁来表示的大体膜损伤发生在pH值低于约4时，在pH值约为3或更低时迅速而广泛地发生。酸性更强的乳酸菌干酪乳杆菌（Lactobacillus casei） ATCC 4646对环境酸化的抵抗力更强，只有在pH值低于3时才会出现明显的膜损伤。在不同pH值的酸脉冲后，对质子进入变形链球菌细胞的运动的评估表明，在pH值约为5时，质子的渗透性最小，在此情况下，细胞膜上的pH平衡平均半时间约为12分钟。酸性较弱的血链球菌对应的pH值为7和8.2 min，中等酸性的唾液链球菌对应的pH值为6和6.6 min。atp酶抑制剂双环己基碳二亚胺的作用显著增加了每个生物体对质子的渗透性，这一作用表明，渗透性不仅包括质子的被动流入，也包括质子通过质子易位膜atp酶的主动流出。结果表明，血链球菌、唾液链球菌、变形链球菌和干酪乳杆菌的atp酶活性最适pH分别为7.5、7.0、6.0和5.0。因此，酶的pH谱反映了细菌的耐酸性和整个细胞对质子的渗透性。
Differences in acid tolerance among representative oral streptococci were found to be related more closely to the dynamic permeabilities of the bacteria to protons than to differences in the sensitivities of cell membranes to gross damage caused by environmental acidification. For Streptococcus mutans GS-5, Streptococcus sanguis NCTC 10904, and Streptococcus salvarius ATCC 13419, gross membrane damage, indicated by the release of magnesium from whole cells, occurred at pH values below about 4 and was rapid and extensive at pH values of about 3 or less. A more aciduric, lactic acid bacterium, Lactobacillus casei ATCC 4646, was more resistant to environmental acidification, and gross membrane damage was evident only at pH values below 3. Assessments of the movements of protons into S. mutans cells after an acid pulse at various pH values indicated that permeability to protons was minimal at a pH value of about 5, at which the average half time for pH equilibration across the cell membrane was about 12 min. The corresponding values for the less aciduric organisms S. sanguis were pH 7 and 8.2 min, and the values for the intermediate organisms S. salivarius were pH 6 and 6.6 min. The ATPase inhibitor dicyclohexylcarbodiimide acted to increase markedly the permeability of each organism to protons, and this action indicated that permeability involved not only the passive inflow of protons but also active outflow through the proton-translocating membrane ATPase. Membranes were isolated from each of the bacteria, and pH profiles for ATPase activities indicated pH optima of about 7.5, 7.0, 6.0, and 5.0 for S. sanguis, S. salivarius, S. mutans, and L. casei, respectively. Thus, the pH profiles for the enzymes reflected the acid tolerances of the bacteria and the permeabilities of whole cells to protons.