Primary Role of NADH Formed by Glucose Dehydrogenase in ATP Provision at the Early Stage of Spore Germination in Bacillus megaterium QM B1551

Abstract

Metabolic events involved in energy metabolism were studied in order to evaluate the ATP-forming ability of Bacillus megaterium QM B1551 spores at the very early stage of germination. When heat-activated spores were germinated on glucose as a sole substrate, its oxidation into gluconate (catalyzed by glucose dehydrogenase, EC 1.1.1.47), the accompanying NADH formation, oxygen uptake, and RNA synthesis were initiated immediately after germination, even when anaerobic breakdown of 3-phosphoglycerate (an ATP source for spores) and the subsequent glucose metabolism via the phosphorylating pathway were impaired by potassium fluoride (KF). In contrast, fructose metabolism and the accompanying metabolic events did not begin until a few minutes after triggering of germination, and those events were entirely abolished by KF, indicating that fructose metabolism is initiated exclusively via its phosphorylation by the ATP derived from endogenous 3-phosphoglycerate. Thus those results provided further evidence for our previous proposal (Otani et al (1987) Microbiol. Immunol. 31: 967-974; Sano et al (1988) Biochem. Biophys. Res. Commun. 151: 48-52) that the first molecules of ATP in germinating spores can be efficiently generated via aerobic oxidation of NADH, which is formed by glucose dehydrogenase. Fluorescence monitoring of NADH in germinating spores also supported this conclusion.