FIGURE 2.

Bacterial densities across all competitions in the presence and absence of both iron and D. discoideum. Bacterial densities in the strains grown separately (i.e., single strains) were divided by 2 to give a per capita measure of cells produced. Horizontal lines represent the mean bacterial density of the strain. Dotted lines represent the mean of Pf2, whereas solid lines represent the means of Pf3 or Pf2ΔgacA. (A) In the presence of D. discoideum and iron-rich media, Pf2 outcompetes Pf3 and Pf2ΔgacA both when it is grown separately and together. (B) However, in the absence of D. discoideum and in the presence of iron, Pf3 and Pf2ΔgacA outcompete Pf2. (C) In iron-limited environments when D. discoideum is present, this pattern is surprisingly maintained. (D) However, when D. discoideum is absent in iron-limited environment, Pf2 grows poorly on its own, and it is able to outcompete Pf3 and Pf2ΔgacA when grown together. This suggests it is acting like a social cheater and exploiting the pyochelin produced by Pf3 and Pf2ΔgacA.