Printed in Great Britain The Physiological Function of Nitrate Reduction

Fermentation-balance studies have been carried out on Clostridium perfringens grown in the presence and absence of nitrate in the medium. Nitrate is able to serve as an electron acceptor for these bacteria, permitting increased growth yields over those obtained in its absence. This increase is due to an increase in the proportion of metabolite molecules which can participate in substrate-level phosphorylation reactions when an inorganic acceptor is available. The nitrate reduction can be regarded as a primitive form of anaerobic respiration in these bacteria, since it is clearly coupled to their energy metabolism and is not assimilative in function. We believe that the existence of this kind of energy metabolism in these bacteria has significant evolutionary implications