Simulated growth rates as a function of altered biomass compositions. Simulated growth rates as a function of altered biomass compositions. Values represent the calculated growth rates associated with a composition of DNA, RNA, lipid, cell wall, and soluble pool which corresponds to each interval of the C/P ratio range. Growth rates were compared by constraining the orthophosphate transporter flux (red) or the carbon fixation flux (black) to suboptimal rates. The number of biomass compositions at each C/P ratio is indicated (n). John R. Casey et al. mSystems 2016; doi:10.1128/mSystems.00065-16