Belli W A, Marquis R E
Department of Microbiology, University of Rochester, New York 14642.
Appl Environ Microbiol. 1991 Apr;57(4):1134-8. doi: 10.1128/aem.57.4.1134-1138.1991.
Streptococcus mutans GS-5 and IB1600 adapted to growth in acidic environments in continuous culture at slow (generation time = 8.3 h) or fast (generation time = 2.4 h) rates of growth in complex medium with a restricted glucose supply. The extent of adaptation was indicated by changes in minimum pH values attained by harvested cells suspended in dense suspensions with excess glucose and by increased levels of ATPase activity assayed in permeabilized cells. Also, adapted cells better withstood potentially lethal acidification. Cells harvested from cultures growing at pH values close to 5 reduced suspension pH to lower values than cells from cultures maintained at pH 7. Cells from pH 6 cultures were intermediate. The IB1600 strain had a higher level of constitutive acid resistance than the GS-5 strain and also was better able to adapt to growth in acidified media. Both had less adaptive capacity than Enterococcus hirae ATCC 9790. Adaptation occurred rapidly, mainly within a single generation in continuous culture, while deadaptation occurred more slowly over multiple generations. The capacity of S. mutans to adapt to acid conditions is likely to be important in the ecology of dental plaque and also for the cariogenicity of the organism.
变形链球菌GS-5和IB1600在复杂培养基中，通过限制葡萄糖供应，以缓慢（代时 = 8.3小时）或快速（代时 = 2.4小时）的生长速率在连续培养中适应酸性环境生长。适应程度通过悬浮在含过量葡萄糖的浓悬液中的收获细胞达到的最低pH值变化以及在透化细胞中测定的ATP酶活性水平升高来表明。此外，适应的细胞更能耐受潜在的致死性酸化。从接近pH 5生长的培养物中收获的细胞比在pH 7维持的培养物中的细胞能将悬浮液pH降低到更低的值。来自pH 6培养物的细胞处于中间状态。IB1600菌株比GS-5菌株具有更高水平的组成型耐酸性，并且也更能适应在酸化培养基中生长。两者的适应能力均低于海氏肠球菌ATCC 9790。适应迅速发生，主要在连续培养的一代内，而脱适应在多代中发生得更慢。变形链球菌适应酸性条件的能力在牙菌斑生态学中以及该生物体的致龋性方面可能很重要。
