FIG 5.

Steady-state concentrations of NO₃⁻ (white bars), NO₂⁻ (gray bars), and NH₄⁺ (black bars) in electron acceptor limiting (high C-to-N ratio) and electron donor limiting (low C-to-N ratio) chemostat cultures of Citrobacter sp. DNRA3 and Enterobacter sp. DNRA5. The N₂O-N production rate (hatched bars) is also presented for Enterobacter sp. DNRA5 cultivated under the electron acceptor limiting condition, which was the only reactor culture with observed N₂O production. The average values of the three measurements taken at 6-h intervals are presented, with error bars representing the standard deviations.