Explaining the sociobiology of pyoverdin producing Pseudomonas: a comment on Zhang and Rainey (2013)

Over the past decade, there has been enormous interest in understanding the great diversity of microbial cooperative behaviors, including communication, group-based swarming, fruiting-body formation, and the secretion of group-beneficial enzymes and food-scavenging molecules. Zhang and Rainey, henceforth Z&R, recently contended that sociomicrobiologists have been overzealous in their casting of microbes as inherently social organisms, and too hasty in interpreting microbial behaviors in a social evolutionary framework. This challenge accompanied a set of experiments in which they revisited one of the best-studied social behaviors in bacteria-the production of diffusible, sharable iron-scavenging siderophore molecules. Z&R posit that their findings challenge the view that siderophore production is a cooperative trait. Here, we demonstrate that their arguments are flawed, and stem from both technical mistakes and misunderstandings of social evolution theory.