Figure 1.

Privatization of siderophore enables the coexistence of partial cooperators and pure cheaters

(A) The schematic diagram of a chemostat model.

(B) The schematic diagram showing two iron uptake fluxes from the public siderophores (left) and private siderophores (right).

(C) The strategy space (the strategic phase diagram) by ternary plot, showing all resource allocation strategies $\overrightarrow{\alpha }=\left({\alpha }_{\mathrm{g}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{h}},{\alpha }_{\mathrm{p}\mathrm{r}\mathrm{i}\mathrm{v}\mathrm{a}\mathrm{t}\mathrm{e}},{\alpha }_{\mathrm{p}\mathrm{u}\mathrm{b}\mathrm{l}\mathrm{i}\mathrm{c}}\right)$. The model has four typical strategies, distinguished according to whether to produce public siderophores and whether to use private siderophores. Pure cooperators (yellow) only produce and use public siderophores, while the pure cheater (orange) only use public siderophores and put all resources into ${\alpha }_{\mathrm{g}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{h}}$; partial cooperators (green) produce and use both public and private siderophores, while self-suppliers (blue) only produce private siderophores and use both public and private siderophores.

(D) The schematic illustration of the four typical strategies shown in (C).

(E and F) The growth contours in the chemical space, with the concentration of Fe³⁺ by the x axis and the concentration of public siderophore by the y axis. (E) shows the growth contours of a pure cooperator and the pure cheater, and (F) shows the growth contours of a partial cooperator and the pure cheater (color scheme same as that in (C) and (D)). The blue area represents a growth-advantageous zone in which the partial cooperator outperforms the pure cheater. Inserts are the biomass time-courses of species competing in the chemostat. The small black dot represents the beginning of the dynamical trajectory (black line).