Small molecules mediate bacterial farming by social amoebae

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The origin of domestication persists as an important question at the nexus between biology, archaeology, and history (1). As intensive research continues apace on organisms whose domestication accompanied the emergence of modern human societies (2, 3), the study of agricultural evolution has expanded to include nonhuman organisms (bark beetles, termites, ants) whose natural history is interwoven with the dispersal, cultivation, and sustainable harvest of microbial symbionts (4). The most recent addition to the roster of nonhuman farmers is Dictyostelium discoideum , a social amoeba that preys upon soil bacteria (5, 6). The life cycle of D. discoideum makes it a favorable model system for the study of cooperation, altruism, and other aspects of social evolution (7⇓–9). When food is scarce, single-celled amoebae aggregate into a multicellular “slug,” which eventually forms a stalked fruiting body from which spores disperse to new habitats. Up to a third of all wild clones of D. discoideum are “farmer strains” that incorporate bacteria into fruiting bodies and establish new food crops during spore dispersal (5), using, as it were, a “take out” foraging strategy that confers advantages under conditions of food scarcity. However, only half of the bacterial cells ( Pseudomonas fluorescens ) carried by farmer strains of D. discoideum are eaten, begging a closer investigation of the bacterial crop to determine whether its domestication reflects hidden costs and benefits of its association with social amoebae. In PNAS, Stallforth et … [↵][1]1E-mail: rar229{at}cornell.edu. [1]: #xref-corresp-1-1