ADAPTATION BY STREPTOCOCCUS-MUTANS TO ACID TOLERANCE
ADAPTATION BY STREPTOCOCCUS-MUTANS TO ACID TOLERANCE
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DOI：
10.1111/j.1399-302x.1991.tb00453.x
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发表时间：
1991-04-01
影响因子：
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通讯作者：
BUCKLEY, ND
中科院分区：
文献类型：
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作者：
HAMILTON, IR;BUCKLEY, ND
我们先前对变形链球菌菌株的连续培养研究表明，该生物体具有适应酸性环境生长的能力。 进行这项研究是为了更详细地审查这一问题。 S.变形链球菌Ingbritt和磷酸转移酶系统（PTS）缺陷型突变体S.在pH7.5和5.5或5.1的连续培养物中生长，并在4.5至8.0的pH范围内用稳态洗涤细胞测定葡萄糖摄取和糖酵解的最佳pH以及细胞产生pH梯度的能力。 此外，通过酸脉冲技术在pH范围内测量细胞的质子渗透性。 结果表明，S.在pH5.5和pH5.1条件下，变形链球菌的最适生长pH分别为7.0和6.0，而在pH7.5条件下，变形链球菌的最适生长pH分别为7.0和6.0。对pH5.5的细胞，最适pH值从7.5变为7.0。 对于2种菌株观察到糖酵解的最佳pH的类似变化，并且这对于在短杆菌肽存在下与葡萄糖孵育以消散质子梯度的细胞特别明显。 细胞产生pH梯度的能力与它们的代谢活性有关，尽管pH 5.5的细胞不能形成较大的梯度，但这些细胞仍然能够在较低的pH下维持梯度; S.在pH5.5时，变形杆菌DR 0001/6产生的pH梯度比S大2倍。变形菌 此外，S.当生长的pH从8.0降低到5.0时，变形杆菌Ingbritt增加4倍。 在pH 7.5和5.5下生长的细胞之间最显著的差异是在2种生物体的质子渗透性曲线中观察到的。 在pH7.5培养的S. pH5.5细胞的Ingbritt值为5.0，变形链球菌的Ingbritt值为6.4，变形链球菌的Ingbritt值为5.0。对于pH7.5和5.5的细胞，变形杆菌DR 0001/6的pH值分别为5.6和4.6。 这表明细胞通过降低质子在较低pH值下进入细胞的渗透性来补偿较低的外部pH。 总的来说，这些结果表明，S。在酸性环境中，例如在裂缝或龋损中可能发现的变形菌，导致细胞生理学的显著变化，从而增加耐酸性。
Our previous continuous culture studies with strains of Streptococcus mutans have indicated that the organism has the capacity of adapt to growth in acidic environments. This study was undertaken to examine this question in more detail. S. mutans Ingbritt and the phosphotransferase system (PTS)-defective mutant, S. mutans DR0001/6, were grown in continuous culture at pH 7.5 and 5.5 or 5.1, and the pH optimum for glucose uptake and glycolysis and the capacity of the cells to generate pH gradients were determined over the pH range 4.5 to 8.0 with steady state, washed cells. In addition, the proton permeability of the cells was measured over the pH range by an acid pulse technique. The results indicate that the pH optimum for glucose uptake by S. mutans Ingbritt grown at pH 7.5 was 7.5 and this optimum shifted to 7.0 and 6.0 for cells grown at pH 5.5 and 5.1, whereas with the S. mutans DR0001/6, the optimum shifted from 7.5 to 7.0 for the pH 5.5 cells. A similar shift in the pH optimum for glycolysis was observed for the 2 strains, and this was particularly pronounced for cells incubated with glucose in the presence of gramicidin to dissipate proton gradients. The capacity of the cells to generate pH gradients was related to their metabolic activity, and although larger gradients were not formed by the pH 5.5 cells, these cells were nevertheless capable of maintaining gradients at a lower pH; S. mutans DR0001/6 generated 2-fold larger pH gradients at pH 5.5 than S. mutans Ingbritt. In addition, activity for the membrane-associated proton-extruding ATPase in S. mutans Ingbritt increased 4-fold as the pH of growth was decreased from 8.0 to 5.0. The most striking difference between cells grown at pH 7.5 and 5.5 was observed in the proton permeability profiles for the 2 organisms. The pH for minimum proton permeability for the pH 7.5-grown cells of S. mutans Ingbritt was 6.4, whereas that for pH 5.5 cells was 5.0; the corresponding values for S. mutans DR0001/6 were pH 5.6 and 4.6 for the pH 7.5 and 5.5 cells, respectively. This indicates that the cells compensate for the lower external pH by decreasing the permeability of protons into the cell at the lower pH values. Collectively, these results indicate that prolonged growth of S. mutans in an acidic environment, such as might be found in fissures or carious lesions, results in significant changes in cell physiology that confer increased acidurance.