Marsh P D, McDermid A S, Keevil C W, Ellwood D C
J Gen Microbiol. 1985 Oct;131(10):2505-14. doi: 10.1099/00221287-131-10-2505.
Carbohydrate metabolism by the oral bacterium Streptococcus sanguis NCTC 7865 was studied using cells grown in a chemostat at pH 7.0 under glucose or amino acid limitation (glucose excess) over a range of growth rates (D = 0.05 h-1-0.4 h-1). A mixed pattern of fermentation products was always produced although higher concentrations of lactate were formed under amino acid limitation. Analysis of culture filtrates showed that arginine was depleted from the medium under all conditions of growth; a further supplement of 10 mM-arginine was also consumed but did not affect cell yields, suggesting that it was not limiting growth. Except at the slowest growth rate (D = 0.05 h-1) under glucose limitation, the activity of the glucose phosphotransferase (PTS) system was insufficient to account for the glucose consumed during growth, emphasizing the importance of an alternative method of hexose transport in the metabolism of oral streptococci. The PTS for a number of sugars was constitutive in S. sanguis NCTC 7865 and, even though the cells were grown in the presence of glucose, the activity of the sucrose-PTS was highest. The glycolytic activity of cells harvested from the chemostat was affected by the substrate, the pH of the environment, and their original conditions of growth. Glucose-limited cells produced more acid than those grown under conditions of glucose excess; at slow growth rates, in particular, greater activities were obtained with sucrose compared with glucose or fructose. Maximum rates of glycolytic activity were obtained at pH 8.0 (except for cells grown at D = 0.4 h-1 where values were highest at pH 7.0), while slow-growing, amino acid-limited cells could not metabolize at pH 5.0. These results are discussed in terms of their possible significance in the ecology of dental plaque and the possible involvement of these bacteria in the initiation but not the clinical progression of a carious lesion.
利用在恒化器中于pH 7.0条件下、在一系列生长速率（D = 0.05 h⁻¹ - 0.4 h⁻¹）下、在葡萄糖或氨基酸限制（葡萄糖过量）条件下培养的血链球菌NCTC 7865细胞，研究了其碳水化合物代谢情况。尽管在氨基酸限制条件下会形成更高浓度的乳酸，但发酵产物总是呈现混合模式。对培养滤液的分析表明，在所有生长条件下，精氨酸都会从培养基中耗尽；额外补充的10 mM精氨酸也会被消耗，但不影响细胞产量，这表明它并非生长限制因素。除了在葡萄糖限制下最慢的生长速率（D = 0.05 h⁻¹）时，葡萄糖磷酸转移酶（PTS）系统的活性不足以解释生长过程中消耗的葡萄糖，这突出了替代己糖转运方法在口腔链球菌代谢中的重要性。多种糖类的PTS在血链球菌NCTC 7865中是组成型的，并且即使细胞在葡萄糖存在的情况下生长，蔗糖 - PTS的活性也是最高的。从恒化器收获的细胞的糖酵解活性受底物、环境pH值及其原始生长条件的影响。葡萄糖限制条件下的细胞比葡萄糖过量条件下生长的细胞产生更多的酸；特别是在缓慢生长速率下，与葡萄糖或果糖相比，蔗糖的糖酵解活性更高。糖酵解活性的最大速率在pH 8.0时获得（在D = 0.4 h⁻¹下生长的细胞除外，其在pH 7.0时活性最高），而生长缓慢、氨基酸限制的细胞在pH 5.0时无法代谢。将根据这些结果在牙菌斑生态学中的可能意义以及这些细菌在龋损起始而非临床进展中的可能参与情况进行讨论。
