A denitrifying activity in an aerobic photosynthetic bacterium, erythrobacter sp. strain OCh 114

An aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh 114, was capable of growth under anaerobic conditions in the dark with nitrate as a terminal electron acceptor. The optimal nitrate concentration was about 6 mM for anaerobic growth, although a wide range of concentrations from 1 to 400 mM were effective. A large amount of N₂O gas was released during this anaerobic growth, indicating a denitrifying activity in this bacterium. Light had no stimulating or inhibiting effect on the rates of anaerobic growth and gas release. The enzymes responsible for the denitrifying activity, dissimilatory nitrate and nitrite reductases, were present in aerobically grown cells.