Figure 3.

Kinetics of O₂ and N₂O respiration. (A) Absorbance at 600 nm (OD₆₀₀), O₂ and N₂O depletion, and production of NO, and N₂ by E. meliloti 1021 when incubated in the presence of 10 mM NO⁻₃ in the medium and an initial O₂ concentration of 2% in the headspace plus 5% N₂O. (B) The electron flow to O₂ or to N₂O is shown as log-transformed values for the oxic (filled circle symbols) and anoxic phase (filled square symbols) with exponential increase. The slopes estimating apparent growth rates were 0.28 (±0.03) h⁻¹ for the oxic phase, and 0.11 (±0.03) h⁻¹ for the anoxic phase, respectively. Cultures with an initial OD₆₀₀ of 0.01 were vigorously stirred at 700 rpm. The result shown is for a single vial. Three replicates were analyzed in parallel with similar results. Consistency of the observations are demonstrated in Table 1 where averages of at least three different cultures are reported.