Abstract
BackgroundBackground: Cytolethal distending toxin (CDT) is one of the well-characterized virulence factors of Campylobacter jejuni, but it is unknown how CDT becomes surface-exposed or is released from the bacterium to the surrounding environment.ResultsOur data suggest that CDT is secreted to the bacterial culture supernatant via outer membrane vesicles (OMVs) released from the bacteria. All three subunits (the CdtA, CdtB, and CdtC proteins) were detected by immunogold labeling and electron microscopy of OMVs. Subcellular fractionation of the bacteria indicated that, apart from the majority of CDT detected in the cytoplasmic compartment, appreciable amounts (20-50%) of the cellular pool of CDT proteins were present in the periplasmic compartment. In the bacterial culture supernatant, we found that a majority of the extracellular CDT was tightly associated with the OMVs. Isolated OMVs could exert the cell distending effects typical of CDT on a human intestinal cell line, indicating that CDT is present there in a biologically active form.ConclusionOur results strongly suggest that the release of outer membrane vesicles is functioning as a route of C. jejuni to deliver all the subunits of CDT toxin (CdtA, CdtB, and CdtC) to the surrounding environment, including infected host tissue.
Highlights
Cytolethal distending toxin (CDT) is one of the well-characterized virulence factors of Campylobacter jejuni, but it is unknown how CDT becomes surface-exposed or is released from the bacterium to the surrounding environment
Analyses of outer membrane vesicles (OMVs) from C. jejuni In order to analyze the surface structure of wild type C. jejuni strain 81-176, we examined the bacteria by atomic
Studies of the OMV samples using electron microscopy revealed that the OMVs from C. jejuni strain 81-176 were somewhat heterogeneous in size with a diameter in the range of 10-50 nm (Figure 1C)
Summary
Background: Cytolethal distending toxin (CDT) is one of the well-characterized virulence factors of Campylobacter jejuni, but it is unknown how CDT becomes surface-exposed or is released from the bacterium to the surrounding environment. Campylobacter jejuni is recognized as the most frequently isolated bacterial cause of food-borne gastroenteritis worldwide. It is found in both developed and developing parts of the world [1,2]. Jain et al described that the presence of the cdtB gene in C. jejuni was associated with increased adherence to, invasion of and cytotoxicity towards HeLa cells [14]. The significant pathological changes in the colons of mice treated with the supernatant containing C. jejuni CDT suggested that CDT is an important virulence attribute and that the colon is the major target of CDT
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