Abstract
Diverse bacteria produce proteinaceous polymeric coils called R-bodies (“refractile bodies”), which extend into ∼10 µm-long needles in response to environmental triggers. It has been proposed that R-bodies deliver toxins intracellularly after such bacteria are ingested by eukaryotes, but intra-host extension of R-bodies has not been directly observed and these toxins remain unidentified. We use Pseudomonas aeruginosa PA14 and Dictyostelium discoideum to show that R-bodies extend within amoebae. We also identify a novel toxin, DeaR ( de aminase a ssociated with the R -body), which contributes to predation resistance and forms a near-megadalton dodecamer with ADP deaminase activity that alters purine metabolism. Our findings elucidate the molecular basis of R-body-mediated toxicity during PA14 infection and provide a paradigm for understanding the potential of c ytotoxic e ffectors d elivered by R -bodies (CEDRs) in interkingdom interactions.
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