Effect of proton balancing on predicted growth rate. The figure shows how limiting the exchange of protons between the cell and the medium affects the predicted growth rates under aerobic conditions. The relative growth rate (y-axis) is the ratio of the predicted growth rate when the proton exchange flux is limited over the predicted growth rate when the proton exchange flux is not limited (at its optimal value). These calculations are for the conditions of aerobic growth on minimal media; the carbon source uptake rates were set to 5 mmol/g DW-hr and the maximum oxygen uptake rate was set to 20 mmol/g DW-hr. Carbon sources resulting in an outward flux of protons (lines to the right of the y-axis) would make the medium more acidic, while carbon sources resulting in an inward flux of protons (lines to the left of the y-axis) would make the medium more basic.
Reed et al. Genome Biology 2003 4:R54 doi:10.1186/gb-2003-4-9-r54