Growth and nitrogenase activity of Azotobacter vinelandii in chemically-defined media containing glucose and p-hydroxybenzoic acid

Azotobacter vinelandii was cultured in chemically-defined media supplemented with p-hydroxybenzoic acid, either in the presence or absence of glucose. Growth, oxygen consumption, nitrogenase activity and utilization of the carbon sources were investigated. When the microorganism was cultured in media containing p-hydroxybenzoic acid and glucose, a biphasic growth curve could be observed, in which glucose was used as primary carbon source. Nitrogenase activity was higher in absence of glucose. Oxygen consumption, however, was lower in media without glucose, suggesting that under these culture conditions the hypothesis of respiratory protection of nitrogenase is not supported.