Journal of Dental Research, Vol 64, 1286-1289, Copyright © 1985 by International & American Associations for Dental Research Online Journals
Anaerobic and aerobic metabolism of sorbitol in Streptococcus sanguis and Streptococcus mitior
G. Svensater, S. Takahashi-Abbe, K. Abbe, D. Birkhed, T. Yamada and S. Edwardsson
Sorbitol-fermenting strains of Streptococcus sanguis and Streptococcus
mitior were grown both anaerobically and in the presence of oxygen in a
sorbitol-containing complex medium. Washed-cell suspensions were incubated
with an excess of sorbitol, and the production of lactate, formate,
ethanol, and acetate was analyzed. Moreover, we determined the lactate
dehydrogenase and pyruvate formate-lyase activities in cell-free extracts
of anaerobically grown cells. The anaerobically grown cells produced
lactate, formate, ethanol, and acetate under anaerobic conditions. When
these cells were exposed to air, the amounts of formate, ethanol, and
acetate were reduced in comparison with those of the strictly anaerobic
cells. Cells grown in the presence of oxygen only produced detectable
levels of lactate and acetate. Anaerobically grown cells possessed lactate
dehydrogenase and pyruvate formate-lyase activities under strictly
anaerobic conditions. The level of pyruvate formate-lyase was dramatically
reduced when cells were exposed to air, while the level of lactate
dehydrogenase was about the same as that under strictly anaerobic
conditions. Thus, the results indicate that S. sanguis and S. mitior both
metabolize sorbitol differently under anaerobic and aerobic conditions.
This difference may depend on the oxygen-sensitivity of the pyruvate
formatelyase of these micro-organisms.
