Abstract
Extracellular vesicles (EVs) recently emerged as important players in the pathophysiology of parasitic infections. While the protist parasite Giardia duodenalis can produce EVs, their role in giardiasis remains obscure. Giardia can disrupt gut microbiota biofilms and transform commensal bacteria into invasive pathobionts at sites devoid of colonizing trophozoites via unknown mechanisms. We hypothesized that Giardia EVs could modify gut bacterial behaviour via a novel mode of trans-kingdom communication. Our findings indicate that Giardia EVs exert bacteriostatic effects on Escherichia coli HB101 and Enterobacter cloacae TW1, increasing their swimming motility. Giardia EVs also decreased the biofilm-forming ability of E. coli HB101 but not by E. cloacae TW1, supporting the hypothesis that these effects are, at least in part, bacteria-selective. E. coli HB101 and E. cloacae TW1 exhibited increased adhesion/invasion onto small intestine epithelial cells when exposed to Giardia EVs. EVs labelled with PKH67 revealed colocalization with E. coli HB101 and E. cloacae TW1 bacterial cells. Small RNA sequencing revealed a high abundance of ribosomal RNA (rRNA)- and transfer RNA (tRNA)-derived small RNAs, short-interfering RNAs (siRNAs) and micro-RNAs (miRNAs) within Giardia EVs. Proteomic analysis of EVs uncovered the presence of RNA chaperones and heat shock proteins that can facilitate the thermal stability of EVs and its sRNA cargo, as well as protein-modifying enzymes. In vitro, RNase heat-treatment assays showed that total RNAs in EVs, but not proteins, are responsible for modulating bacterial swimming motility and biofilm formation. G. duodenalis small RNAs of EVs, but not proteins, were responsible for the increased bacterial adhesion to intestinal epithelial cells induced upon exposure to Giardia EVs. Together, the findings indicate that Giardia EVs contain a heat-stable, RNase-sensitive cargo that can trigger the development of pathobiont characteristics in Enterobacteria, depicting a novel trans-kingdom cross-talk in the gut.