Fig. 10

Reactor cells in fresh medium (Bioassay 4). Vials with He-atmosphere and 50 mL mineral medium with glucose were inoculated with cells (8·10¹⁰ cells vial⁻¹) from the bioreactor and monitored for N gas kinetics while stirred at 30°C. Four vials were provided with N₂O as the sole electron acceptor (~ 1 vol% N₂O in the headspace = 41 µmol vial⁻¹), while four vials were provided with NO₂⁻ as the sole electron acceptor (2 mM KNO₂ in the liquid). The large show the measured amount of NO, N₂O, and N₂ per vial (average, with standard deviation as vertical lines, n = 4), and the cell numbers per vial (calculated from the cumulated respiratory electron flow). The inserts show the cell-specific rates of N₂-production (V_N2, fmol N cell⁻¹ h⁻¹) and electron flow (V_e, fmol e⁻ cell⁻¹ h⁻¹). For the N₂O-fed cultures (left), only V_N2 is shown because V_e equals V_N2 (1 electron per N). The dotted line represents V_max in cells with µ = 0.19 h⁻¹ assuming yield = 1.93 · 10¹³ cells mol⁻¹ e⁻ to NO₃- [27]