Figure 6.

Conceptual scheme of the four approaches to model mixed microbial cultures using stoichiometric metabolic networks. In all figures boxes S^A, S^B, S^C represent sets of equations (captured as an S matrix) of metabolic reactions occurring in organisms/guilds A, B, and C, respectively. S^ABC is a matrix lumping metabolic reactions occurring in organisms/guilds A, B, and C. These sets of reactions can have any number of sub compartments to model reactions occurring in the extracellular space and organelles; boxes with dashed lines indicate model (system) boundaries; boxes with solid lines indicate guild boundaries; v_j is the flux of metabolite in reaction j; V is the vector of fluxes estimated by the model; V^k is the vector of fluxes estimated by the model of species/guild k (A, B, or C); X_i is the concentration of metabolite i; μ^k (a.k.a. $v_{biomass}^k$) is the growth rate (biomass production rate) of species k; f^k is the fraction of species k in community's biomass; and $X_{biomass}^k$ is the biomass concentration of modeled species/guild k (A, B, or C). Figure inspired in Taffs et al. (2009) modeling approaches diagrams.