Fig. 3.

Adaptation to low iron availability. (A) Competitive, cheating, and cooperative behaviors among single-cell organisms. Siderophore secretion allows iron acquisition from mineralized sources but also leads to complex interactions between bacterial cells and species, which may drive genetic variation. (B) Trafficking of iron in development of eukaryotes (mitochondria), phagocytosis (predation), intracellular infection, and multicellularity. In these processes, biotic sources of iron are utilized in behaviors that can be mutually beneficial, piratical, or more efficiently self-sufficient.