FIG. 2.

Concentrations of NO₂⁻ as functions of time in two experiments with either NO₃⁻ added (A) or NO₂⁻ added (B). The solid lines indicate the theoretical decrease in NO₂⁻ concentration assuming Michaelis-Menten kinetics and a K_m value of 0.1 μM, a maximum NO₂⁻ reduction rate calculated as the slope of the linear portion of the curve, and an initial concentration calculated as the intersection of this linear regression with the y axis. The other lines depict the decrease in NO₂⁻ concentration assuming higher K_m values. Error bars indicate standard errors.