Abstract
The possibility of gaseous nitrogen release from water bodies under aerobic condition was investigated by using natural water and pure cultures of denitrifying bacteria.
1) Total nitrogen concentration (KJELDAHL-N+NO2-N+NO3-N) did not decrease during the processes of aerobic degradation of nitrogenous organic compounds and nitrification in the pond water enriched with seston, ammonium sulfate or a medium for nitrifying bacteria. Gaseous nitrogen release was not likely to occur in these processes.
2) Denitrification did not seem also to occur in the growing cultures of the denitrifying bacteria, Pseudomonas aeruginosa and Pseudomonas No.7, incubated with nitrate under aerobic condition, since total nitrogen was constant during incubation.
3) Cells of Pseudomonas No. 7 grown aerobically were not able to reduce nitrite and nitrate under aerobic condition. However, cells of Pseudomonas No. 7 previously grown anaerobically reduced nitrite under aerobic condition as rapidly as under anaerobic condition, although they did not reduce nitrate. This result may indicate the possibility of denitrification from nitrite under aerobic condition. It seems, however, to be doubtful that this reaction occurs with significant rate in natural water.
