We measured N2O production by two species of primary chemoautotrophic nitrifying bacteria, Nitrosomonas europaea and Nitrosolobus multiformis, in media with different dissolved O2 concentrations. Both species produced N2O across a wide range of O2 concentrations and after 48 h there was a large peak of N2O production (3.2 nmol N2O cm-3 cell suspension) by N. europaea at a dissolved concentration of 2.1 mg O2 1-1, whereas for N. multiformis the peak in N2O production was much smaller (1.6 nmol N2O cm-1), but it also occurred at a dissolved O2 concentration of 2.1 mg O2 1-1. However at greater dissolved oxygen concentrations (between 24 and 37 mg O2 1-1), N. multiformis produced more N2O than N. europaea. The results are consistent with both species producing N2O during NH4+ oxidation and with N. europaea, producing a much larger amount of N2O during denitrification than N. multiformis.
- Nitrifer denitrification
- Nitrous oxide