Energy metabolism in Capnocytophaga ochracea

Among the microflora of the gingival sulcus are members of the genus Capnocytophaga which have been implicated as possible etiological agents of juvenile periodontitis and systemic infectious diseases. In this study, the pathway used by C. ochracea strain 25 for generating energy from glucose was investigated. When grown in a complex medium supplemented with glucose and NaHCO(3), the major end products formed were acetate (4.6 mmol), succinate (11.0 mmol), pyruvate (4.3 mmol), and oxalacetate (3.6 mmol), and the molar growth yield was 58. Addition of yeast extract to the growth medium caused (i) an increase in acetate (9.2 mmol) and succinate (14.3 mmol), (ii) a decrease in pyruvate (0 mmol) and oxalacetate (1.1 mmol), and (iii) the molar growth yield increased to 75. Glucose was transported by a phosphoenolpyruvate:phosphotransferase system and then catabolized to phosphoenolpyruvate by enzymes of the Embden-Meyerhof-Parnas pathway. No activities were detected for the key enzymes of the Warburg-Dickens, Entner-Douderoff, or hexose phosphoketolase pathways. During growth in the yeast extract-supplemented medium, approximately 37% of the phosphoenolpyruvate carbon was converted to acetate by pyruvate kinase, a pyruvate-decarboxylating enzyme activity, and acetate kinase; the remaining 63% was converted to succinate via phosphoenolpyruvate carboxykinase, malate dehydrogenase, fumarate hydratase, and fumarate reductase.