title: Biogenesis of outer membrane vesicles in Serratia marcescens is thermoregulated and can be induced by activation of the Rcs phosphorelay system.
abstract: Outer membrane vesicles (OMVs) have been identified in a wide range of bacteria, yet little is known of their biogenesis. It has been proposed that OMVs can act as long-range toxin delivery vectors and as a novel stress response. We have found that the formation of OMVs in the gram-negative opportunistic pathogen Serratia marcescens is thermoregulated, with a significant amount of OMVs produced at 22 or 30°C and negligible quantities formed at 37°C under laboratory conditions. Inactivation of the synthesis of the enterobacterial common antigen (ECA) resulted in a hypervesiculation phenotype, supporting the hypothesis that OMVs are produced in response to stress. We demonstrate that the phenotype can be reversed to wild-type (WT) levels upon the loss of the Rcs phosphorelay response regulator RcsB, but not RcsA, suggesting a role for the Rcs phosphorelay in the production of OMVs. MS fingerprinting of the OMVs provided evidence of cargo selection within wild-type cells, suggesting a possible role for Serratia OMVs in toxin delivery. In addition, OMV-associated cargo proved toxic upon injection into the haemocoel of Galleria mellonella larvae. These experiments demonstrate that OMVs are the result of a regulated process in Serratia and suggest that OMVs could play a role in virulence.
authors.affiliation: Alberta Glycomics Centre, Department of Biological Sciences, University of Alberta, Alberta, Canada.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: McMahon
authors.forename: Maria E
authors.initials: ME
authors.lastname: Castelli
authors.forename: Eleonora
authors.initials: E
authors.lastname: García Vescovi
authors.forename: Mario F
authors.initials: MF
authors.lastname: Feldman
mesh_terms: D000818:Animals; D015964:Gene Expression Regulation, Bacterial; D007814:Larva / Q000382:microbiology; D007915:Lepidoptera / Q000382:microbiology; D022142:Secretory Vesicles / Q000378:metabolism*; D012706:Serratia marcescens / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity / Q000528:radiation effects; D015398:Signal Transduction; D013312:Stress, Physiological; D016019:Survival Analysis; D013696:Temperature; D014774:Virulence