Energy metabolism of some representatives of the Haemophilus group

Abstract

The purpose of this investigation was to characterize the carbohydrate catabolism and the constellation of the respiratory chain components of Haemophilus influenzae RAMC 18 Bensted, H. parainfluenzae 1 Fleming, H. parainfluenzae 429 Pittman and H. aegyptius 180a Pittman. These strains represent several physiological types with respect to respiratory quinones and glucose catabolism. On addition of glucose or lactate to the complex growth medium a remarkable increase in cell mass was observed. Depending on the growth rate, carbohydrate degradation varied with the strains examined so that at the end of the exponential growth phase only small amounts of the supplements could be demonstrated. All strains were found to possess functional enzymes of Embden-Meyerhof-Parnas-, Entner-Doudoroff-pathways, hexosemonophosphate shunt, tricarboxylic acid cycle and gluconeogenesis with an extremely high activity of malate dehydrogenase. The concentration of cytochromes varied according to culture conditions. The cytochromes a₁, d, o and b+c were found to occur under aerobic conditions. In cells grown anaerobically in the presence of fumarate cytochromes a₁ and d could not be demonstrated. Under aerobic conditions preparations of H. parainfluenzae 1 Fleming exhibited an α-maximum at 558 nm, whereas under anaerobic culture conditions with fumarate as terminal electron acceptor an α-maximum at 552 nm occurred, suggesting different roles of b and c type cytochromes in aerobic and anaerobic electron transport to fumarate, respectively.