Research article

Outer membrane vesicle-mediated release of cytolethal distending toxin (CDT) from Campylobacter jejuni

Barbro Lindmark¹ , Pramod Kumar Rompikuntal¹ , Karolis Vaitkevicius¹ , Tianyan Song¹ , Yoshimitsu Mizunoe² , Bernt Eric Uhlin^1,3 , Patricia Guerry⁴ and Sun Nyunt Wai¹

¹Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden

²Department of Bacteriology, the Jikei University School of Medicine, Tokyo 105-8461, Japan

³Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, S-90187 Umeå, Sweden

⁴Enteric Diseases Department, Naval Medical Research Center, 503 Robert Grant Ave, Silver Spring, MD, USA

author email corresponding author email

BMC Microbiology 2009, 9:220doi:10.1186/1471-2180-9-220

Published:	16 October 2009

Abstract

Background

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.

Results

Our 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.

Conclusion

Our 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.