Figure 5. A model of phototrophic growth and reproduction of experimental growth curves.

Panel A: A coarse-grained model of phototrophic growth, adopted from Faizi et al. (2018). The model describes optimal proteome allocation under conditions of (i) light-limited, (ii) light-saturated and (iii) light-inhibited growth. Coarse-grained cellular processes include passive ($v_d$) and active import ($v_t$) of external inorganic carbon $c_i^x$, conversion of inorganic carbon $c_i$ into amino acids $aa$ ($v_m$), light harvesting and provision of cellular energy by photosynthesis ($v_1$ and $v_2$), as well as maintenance and photodamage ($m_v$ and $v_i$). Amino acids are translated into coarse-grained protein fractions for transport ($T$), metabolism ($M$), ribosomes ($R$), photosynthetic electron transport ($P$), as well as a growth-independent proteome fraction $Q$. Translation is limited by the amount of available ribosomes $R$. Panel B: The model reproduces the measured growth curve (Figure 1C–D) as a function of light intensity. Shown are the specific growth rate μ, as well as the main proteome fractions predicted by the model: ribosome ($R$) fraction, photosynthetic electron transport ($P$) fraction, and metabolism ($M$) fraction, as a function of light intensity.