FIG. 3.

Denitrification activities of P. aeruginosa biofilms grown under low-oxygen partial pressure conditions. PAO1 (circles) and PS1700 (squares) were grown with (solid) or without (open) KNO₃. (A and B) NO₃⁻ (A) and NO₂⁻ (B) concentrations in the effluent flow. (C and D) Amount of N₂ (C) and N₂O (D) that accumulated in the gas collector. The amount of N₂ is calculated as the difference between total N₂ and background accumulation of N₂. Negative values of N₂ are expressed as 0 μmol. Data are the averages of three biofilm cultures. Error bars indicate standard deviations.