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Environmental regulation of carbohydrate metabolism by Streptococcus sanguis NCTC 7865 grown in a chemostat

Environmental regulation of carbohydrate metabolism by Streptococcus sanguis NCTC 7865 grown in a chemostat
Environmental regulation of carbohydrate metabolism by Streptococcus sanguis NCTC 7865 grown in a chemostat

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.

0022-1287
2505-2514
Marsh, P. D.
9d226405-bfd2-432b-ac22-ea619f706805
McDermid, A. S.
34686047-11ba-41da-884d-1dc41fa7024b
Keevil, C. W.
cb7de0a7-ce33-4cfa-af52-07f99e5650eb
Ellwood, D. C.
a7dc8f2a-f392-42b4-a022-fa5a58cf6be6
Marsh, P. D.
9d226405-bfd2-432b-ac22-ea619f706805
McDermid, A. S.
34686047-11ba-41da-884d-1dc41fa7024b
Keevil, C. W.
cb7de0a7-ce33-4cfa-af52-07f99e5650eb
Ellwood, D. C.
a7dc8f2a-f392-42b4-a022-fa5a58cf6be6

Marsh, P. D., McDermid, A. S., Keevil, C. W. and Ellwood, D. C. (1985) Environmental regulation of carbohydrate metabolism by Streptococcus sanguis NCTC 7865 grown in a chemostat. Journal of General Microbiology, 131 (10), 2505-2514. (doi:10.1099/00221287-131-10-2505).

Record type: Article

Abstract

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.

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Published date: 1 October 1985

Identifiers

Local EPrints ID: 431318
URI: http://eprints.soton.ac.uk/id/eprint/431318
ISSN: 0022-1287
PURE UUID: 05e15928-672d-4cfe-b6a8-0330b14ec34e
ORCID for C. W. Keevil: ORCID iD orcid.org/0000-0003-1917-7706

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Date deposited: 29 May 2019 16:30
Last modified: 30 May 2019 00:36

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Contributors

Author: P. D. Marsh
Author: A. S. McDermid
Author: C. W. Keevil ORCID iD
Author: D. C. Ellwood

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