Fig. 5.

Influence of pH on activity of denitrifying enzymes in washed cells of Halomonas strain AGD 3 grown at 2 M Na⁺, pH 10. The cells were tested at 2 M Na⁺ with 10 mM acetate as the electron donor and 5 mM of nitrate (nitrate-grown cells open circles), nitrite (nitrite-grown cells closed circles) or N₂O (N₂O-grown cells open triangles). The following buffer systems were used: for pH 7–8, HEPES/NaCl; pH 8.5–11.5, NaHCO₃/Na₂CO₃; pH 12, Na₂CO₃/NaOH. Incubation time, 4 h; cell concentration, 0.6 mg protein/ml. One hundred percent activity: nitrate reductase = 240, nitrite reductase = 190 and N₂O reductase = 150 nmol/(mg protein min)