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J Bacteriol. 1968 November; 96(5): 1595-1600
Copyright © 1968 American Society for Microbiology. All Rights Reserved.

Molar Growth Yields as Evidence for Oxidative Phosphorylation in Streptococcus faecalis Strain 10C1¹

^a Microbiology Section, Division of Biological Sciences, Cornell University, Ithaca, New York 14850

ABSTRACT

During the aerobic growth of Streptococcus faecalis strain 10C1, with limiting levels of glucose as the substrate, a molar growth yield (Y) of 58.2 g (dry weight) per mole of glucose was obtained. Under these conditions of growth, glucose was dissimilated primarily to acetate and CO₂. The incorporation of ¹⁴C-glucose into cell material was no greater under aerobic conditions than during anaerobic growth. Assuming an adenosine triphosphate coefficient of 10.5, the aerobic Y cannot be explained solely on the basis of substrate phosphorylation and would appear to substantiate previous enzymatic evidence for oxidative phosphorylation in this cytochromeless species. With mannitol as the substrate, an aerobic Y of 64.6 was obtained. Extracts of mannitol-grown cells contained a nicotinamide adenine dinucleotide (NAD)-linked mannitol-1-phosphate (M-1-P) dehydrogenase. The difference in aerobic Y values with mannitol and glucose as substrates would indicate that the in vivo P/O ratio from the oxidation of reduced NAD generated by the oxidation of M-1-P approximates 0.6. The Y values with pyruvate and glycerol as substrates under aerobic conditions were 15.5 and 24.7, respectively.

¹ A preliminary report of this study was presented at the 67th Annual Meeting of the American Society for Microbiology; New York, N.Y., 30 April to 4 May, 1967. This work was presented in part in a thesis by the senior author to the Graduate Faculty of Cornell University in partial fulfillment of the requirements for the degree of Master of Science.