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


CONCLUSIONS
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.
Lindmark
Barbro
B
Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden. barbro.lindmark@molbiol.umu.se
Rompikuntal
Pramod Kumar
PK
Vaitkevicius
Karolis
K
Song
Tianyan
T
Mizunoe
Yoshimitsu
Y
Uhlin
Bernt Eric
BE
Guerry
Patricia
P
Wai
Sun Nyunt
SN
D001427:Bacterial Toxins / Q000378:metabolism*; D016123:Campylobacter jejuni / Q000378:metabolism*; D045744:Cell Line, Tumor; D006801:Humans; D018625:Microscopy, Atomic Force; D016253:Microscopy, Immunoelectron; D022161:Transport Vesicles / Q000378:metabolism* / Q000382:microbiology
D001427:Bacterial Toxins; C067044:cytolethal distending toxin