Path of Glucose Breakdown and Cell Yields of a Facultative Anaerobe, Actinomyces naeslundii

SUMMARY: Actinomyces naeslundii fermented glucose primarily by the Embden-Meyerhof pathway, as based on 14C-glucose fermentation data and enzyme studies. Enzymes of the oxidative pentose phosphate cycle were also present, but functioned only to a minor extent. Growth on glucose was increased 2-to 4-fold in the presence of substrate amounts of CO2 or O2. This increase was attributed to the additional energy (ATP) made available from the breakdown of pyruvate to acetyl coenzyme A. In the absence of CO2 or O2, pyruvate was reduced to lactate. The weight of organism produced/mole ATP (Y ATP) was 15-18 g. units under anaerobic conditions with CO2, dependent on the growth medium, and 20 under aerobic growth conditions.