Respiration per protein as a function of C/N.
Data (points) are shown as well as results of two simulation models. In one simulation (Sim1) energetically excess respiration can occur both during nitrogen fixation and during nitrogen limited growth on ammonium. In the second model (Sim2) excess respiration is allowed only during nitrogen fixation. Sim1 and Sim2 produce same amount of biomass. (i) 30% O2 and (ii) 60% O2. Solids lines and points are same as Fig 3B. The dilution rate is constant of 0.15 h-1, and red dashed lines show borders between different regimes (A: Carbohydrate limited, B: Ammonium limited, C: Nitrogen fixing as defined in Fig 5). Here 100% O2 equals 225 μM thus approximately O2 saturation under normal air composition at 30°C.