TY - JOUR
T1 - Environmental regulation of carbohydrate metabolism by Streptococcus sanguis NCTC 7865 grown in a chemostat
AU - Marsh, P. D.
AU - McDermid, A. S.
AU - Keevil, C. W.
AU - Ellwood, D. C.
PY - 1985
Y1 - 1985
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0022379015&partnerID=8YFLogxK
U2 - 10.1099/00221287-131-10-2505
DO - 10.1099/00221287-131-10-2505
M3 - Article
C2 - 2999295
AN - SCOPUS:0022379015
SN - 0022-1287
VL - 131
SP - 2505
EP - 2514
JO - Journal of General Microbiology
JF - Journal of General Microbiology
IS - 10
ER -