| Popis: |
Five electron were compared for their effects on respiration and nitrogenase activity in Azotobacter vinelandii . Metronidazole, menadione bisulfite, nitroblue tetrazolium, methyl viologen and benzyl violagen all inhibited nitrogenase activity. The electron acceptors did not significantly decrease oxygen uptake when nitrogenase activity was inhibited by about 40%. Concentrations of ATP, ADP and AMP were no altered by incubation with metronidazole or menadione bisulfite. Menadione bisulfite and nitroblue tetrazolium inhibited oxygen uptake by a cell fraction containing respiratory membrane particles. The fraction catalyzed the reduction of methyl viologten, benzyl viologen and niroblue tetrazolium but metronidazole reduction was not detected. These results indicate that metronidazole is the most selective of the acceptors for low-potential processes, but during steady-state conditions other electron acceptors can be equally selective. This selectivity apparently arises from reductant production that is in excess of that needed for respiration. |
