Table 4.

Maximum rates of nitrite and oxygen consumption and nitrous oxide production by stationary phase S. wittichii RW1 wildtype cultures grown at atmospheric (ca. 22%) or reduced (ca. 3%) O₂ headspace.

NaNO2 (mM) added to growth medium	Rate of O2 consumption (% headspaceOD−1 h−1)		Rate of NO−2 consumption (μmolOD−1 h−1)		Rate of N2O production (nmolOD−1 h−1)
	Atmos. O2	Red. O2	Atmos. O2	Red. O2	Atmos. O2	Red. O2
0	0.03	0.02	0	0	0	0
0.3	0.03	0.02	0.9	0.9	5.2*	16.1*
1.0	0.04*	0.02*	2.2*	1.5*	13.9*	29.8*

Values represent slopes of averaged measurements from 5 experiments initiated on different cultures and on different days (y-axis) over time (48–72 h; x-axis). The “

^*” indicates a significant difference between incubations initiated at atmospheric or reduced (3%) O₂ headspace as determined by Student's t-test (p < 0.05). Calculated rates of were normalized to OD units of the cultures due to the difference in maximum biomass between cultures (Table 2).