Intra- and Interspecific Siderophore Cheating in Bacteria.  The evolution of cooperation remains a central paradox in biology: Why should an individual carry out a costly cooperative behavior for the benefit of others?  Cooperative iron acquisition via diffusible siderophores offers a tractable bacterial model for mechanistic inquiry.  It is a widespread and vitally important process in many microbes, with implications in soil ecology, agriculture, and medicine.  Intriguingly, some bacteria have the ability to steal siderophores from other bacteria, thus saving on production costs.  We plan to find out how and why cooperative iron acquisition is nevertheless maintained.