8 research outputs found
Nitrification by heterotrophic denitrifiers and its relationship to autotrophic nitrification
Applied Science
A mathematical description of the behaviour of mixed chemostat cultures of an autotrophic nitrifier and a heterotrophic nitrifier/aerobic denitrifier; a comparison with experimental data
Rapid Short-Term Poly-ß-Hydroxybutyrate Production by Thiosphaera-Pantotropha in the Presence of Excess Acetate
Simultaneous nitrification and denitrification in aerobic chemostat cultures of Thiosphaera pantotropha
Heterotrophic Nitrification and Aerobic Denitrification in Alcaligenes-Faecalis Strain TUD
Competition between Heterotrophic and Autotrophic Nitrifiers for Ammonia in Chemostat Cultures
Mixed cultures of a heterotrophic nitrifier/aerobic denitrifier, Thiosphaera pantotropha, and an autotrophic nitrifier, Nitrosomonas europaea, were grown in chemostats under dual ammonia-and acetate limitation. Because of simultaneous nitrification and denitrification by T. pantotropha, the activity of the cultures was evaluated from nitrogen balances as complete as possible. Under most conditions studied, no interaction took place between the two bacteria. Only above a critical C/N ratio of 10.4, T. pantotropha was able to outcompete N. europaea for ammonia (dilution rate = 0.04 h−1). At dissolved oxygen concentrations below 10 μM, the autotroph became oxygen-limited and the heterotroph dominated in the culture. Moreover, when the dilution rate was increased to 0.065 h−1, N. europaea could not maintain itself successfully in the chemostat, even when the C/N ratio was as low as 2.2. Nitrification by T. pantotropha was equivalent to that of N. europaea when the cell ratio of heterotrophs/autotrophs was 250. The relevance of these observations to the nitrogen cycle in natural environments is discussed