FIG 2.

Percentage of NO₂⁻ production compared to the uninhibited control (C) after 1 h of incubation with different concentrations of hydrazine using 100 μM NH₄⁺ as the substrate. NO₂⁻ was measured 1 h after the addition of the substrate. Nitrite accumulation in the uninhibited control treatment represents 100% activity, and the treatments with hydrazine are shown as percentages of activity compared to this control. Error bars represent standard deviations (n = 3). One hundred percent activity corresponded to 100 μM, 59 μM, 54 μM, and 63 μM nitrite accumulated after 1 h in (A) “Ca. Nitrosocosmicus franklandus,” (B) N. europaea, (C) N. viennensis, and (D) “Ca. Nitrosotalea sinensis,” respectively.