Predation-resistantPseudomonasbacteria engage in symbiont-like behavior with the social amoebaDictyostelium discoideum

Abstract

AbstractThe soil amoebaDictyostelium discoideumacts as both a predator and potential host for diverse bacteria. We tested fifteenPseudomonasstrains that were isolated from transiently infected wildD. discoideumfor ability to escape predation and infectD. discoideumfruiting bodies. Three predation-resistant strains frequently caused extracellular infections of fruiting bodies but were not found within spores. Furthermore, infection by one of these species induces secondary infections and suppresses predation of otherwise edible bacteria. Another strain can persist inside of amoebae after being phagocytosed but is rarely ingested. We sequenced isolate genomes and discovered that predation-resistant isolates are not monophyletic. ManyPseudomonasisolates encode secretion systems and toxins known to improve resistance to phagocytosis in other species, as well as diverse secondary metabolite biosynthetic gene clusters that may contribute to predation resistance. However, the distribution of these genes alone cannot explain why some strains are edible and others are not. Each lineage may employ a unique mechanism for resistance.