No abstract

The mechanisms used by Campylobacter jejuni to colonize the (chicken) intestinal tract have not been defined. In this study, we obtained evidence that in the presence of chicken serum and mucus, C. jejuni secreted proteins that may play a role in the colonization of chicken gut (Campylobacter invasion antigen = Cia). C. jejuni strains NCTC11168V1 and 81-176, as well as an NCTC11168V1 flaA mutant, were found to colonize intestinal tract and secrete proteins in the presence of chicken mucus, chicken serum, or fetal bovine serum in cell culture-conditioned medium. C. jejuni strain NCTC11168V26, which was observed to be a poor colonizer compared with the other C. jejuni isolates, did not secrete Cia proteins. Secreted proteins were also recognized by Western immunoblot using sera from birds that had been colonized by C. jejuni. These data suggest that C. jejuni secretes Cia proteins during colonization of chicken gut and that these Cia proteins play an important role in colonization.

No abstract

NADPH oxidase (NOX) is one of the sources of reactive oxygen species (ROS) that modulates the activity of proteins through modifications of their cysteine residues. In a previous study, we demonstrated the importance of NOX in both the development and pathogenicity of the phytopathogen Fusarium graminearum. In this article, comparative proteomics between the wild-type and a Nox mutant of F. graminearum was used to identify active cysteine residues on candidate redox-sensing proteins. A two-dimensional gel approach based on labelling with monobromobimane (mBBR) identified 19 candidate proteins, and was complemented with a gel-free shotgun approach based on a biotin switch method, which yielded 99 candidates. The results indicated that, in addition to temporal regulation, a large number of primary metabolic enzymes are potentially targeted by NoxAB-generated ROS. Targeted disruption of these metabolic genes showed that, although some are dispensable, others are essential. In addition to metabolic enzymes, developmental proteins, such as the Woronin body major protein (FGSG_08737) and a glycosylphosphatidylinositol (GPI)-anchored protein (FGSG_10089), were also identified. Deletion of either of these genes reduced the virulence of F. graminearum. Furthermore, changing the redox-modified cysteine (Cys ) residue in FGSG_10089 to either serine or phenylalanine resulted in a similar phenotype to the FGSG_10089 knockout strain, which displayed reduced virulence and altered cell wall morphology; this underscores the importance of Cys to the function of the protein. Our results indicate that NOX-generated ROS act as intracellular signals in F. graminearum and modulate the activity of proteins affecting development and virulence in planta.

Campylobacter jejuni produces cytolethal distending toxin (CDT) that causes host cells to arrest during their cell cycle and that is involved in the pathogenesis of inflammatory diarrhea in humans. To assess the role of CDT in adherence and invasion of different cultured host cells (HeLa and HD-11) and in colonization of the chicken intestine, the genes of C jejuni NCTC11168 encoding the toxin subunits (cdtA, cdtB, and cdtC) were inactivated by insertional mutagenesis. No significant difference was found in adhesion of the wild-type C. jejuni and the isogenic mutants to HeLa and HD-11 cells. All of the mutants exhibited a decrease (>10-fold) in the ability to invade HeLa cells, but no significant difference was noticed for HD-11 cells. The ability of mutants to colonize birds either directly or by horizontal transfer was unchanged. These data indicated that although the production of cytotoxin does not play a role in the adherence to either human or avian cells, it may play a role in the invasion, survival, or both of C. jejuni in human cells, which are more susceptible to C. jejuni internalization. The CDT also does not seem to play a role in the colonization of poultry.