FIG 8.

Modeled curves of O₂ consumption (R) of hypothetical spherical cells otherwise having characteristics similar to those of the M. daepoensis cells investigated under the following assumptions. (i) The cell consumes all oxygen diffusing to the cell so that the O₂ concentration at the cell surface is zero (J_max). (ii) The cell terminal oxidases exhibit Michaelis-Menten kinetics, but there is no diffusion limitation (R_max). (iii) The O₂ consumption by the cell is limited by both enzyme kinetics and diffusion to the cell (R_c). The modeling was performed under three scenarios: big cells (diameter, 1.47 μm) with a high respiration rate (2.53 fmol O₂ cell⁻¹ h⁻¹) under nonlimiting O₂ concentrations (V_max) and only a low-affinity terminal oxidase (K_m value, 200 nmol liter⁻¹) (A), big cells with a high respiration rate and only a high-affinity terminal oxidase (K_m value, 5 nmol liter⁻¹) (B), and small cells (diameter, 1.01 μm) with a low respiration rate (0.20 fmol O₂ cell⁻¹ h⁻¹) and only a high-affinity terminal oxidase (C).