Comment on Egami's concept of the evolution of nitrate respiration

Recent results suggest that the presence of common nitrogen salts (sodium nitrite and nitrate) in the irradiation medium can markedly protect filamentous blue-green algae from potentially lethal ultraviolet irradiation. The present results as well as general biological arguments of Egami support and extend Egami's original view that anaerobic respiratory pathways using nitrite and nitrate as terminal electron acceptors evolved prior to oxygen requiring aerobic respiratory pathways.