Submitted to: Journal of Proteome Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/17/2007
Publication Date: 11/1/2007
Citation: Seal, B.S., Hiett, K.L., Kuntz, R.L., Woolsey, R., Schegg, K., Ard, M., Stintzi, A. Proteomic Analyses of a Robust versus a Poor Chicken Gastrointestinal Colonizing Isolate of Campylobacter jejuni. Journal of Proteome Research. 6:4582-4591. Interpretive Summary: The Centers for Disease Control and Prevention estimates that Campylobacter spp. are one of the leading bacterial causes of human food-borne illness in the United States. While these bacteria are associated with a variety of foods, the handling and consumption of poultry or poultry related products is considered to be a source for bacterial food-borne disease in humans. While pathogenic in a variety of hosts such as humans, Campylobacter spp. exists in an apparently commensal relationship with poultry. The pathways involved in contamination of poultry flocks by these pathogens continue to remain unclear, therefore, effective intervention strategies are still lacking for the poultry industry. Additionally, the mechanisms of how these bacteria interact with their host and how these organisms colonize poultry are not well defined. The identification of genes and gene products involved in Campylobacter spp. colonization of chickens is necessary for the development of intervention strategies aimed at the reduction or elimination of Campylobacter spp. in poultry. Therefore, the expression of proteins from a C. jejuni isolate that is considered a very good colonizer of chickens was compared to the proteins expressed by a C. jejuni isolate that does not colonize the chicken gastrointestinal tract in as high of numbers. It was determined that proteins expressed by the good chicken colonizing C. jejuni isolate were those thought to be involved with attachment of the bacteria to host cells. Also, it was determined that many genes involved with the bacteria to survive in biofilms were also found in the bacteria that were good at colonizing the chicken gastrointestinal tract. Consequently, if interventions can be developed that disrupt specific biological functions of C. jejuni, such as attachment of the bacteria to chicken gastrointestinal cells, these bacteria could be reduced in chickens prior to processing for human consumption.
Technical Abstract: Campylobacter spp. are a significant contributor to the bacterial etiology of acute gastroenteritis in humans. Epidemiological evidence implicates poultry as a major source of the organism for human illness. However, the factors involved in colonization of poultry with Campylobacter spp. remain unclear. Determining colonization-associated factors at the proteome level should facilitate our understanding of Campylobacter spp. contamination of poultry. Therefore, proteomic analyses were utilized to identify expression differences between two Campylobacter jejuni isolates, a robust colonizer A74/C and a poor colonizing strain of the chicken gastrointestinal system designated NCTC 11168-PMSRU. Proteomic analyses by two-dimensional gel electrophoresis revealed the specific expression of an outer membrane-fibronectin binding protein, branched chain amino acid ABC transport protein, serine protease and a putative aminopeptidase in the soluble portion of the robust colonizer A74C. Several proteins including a cysteine synthase and aconitate hydratase were detected specifically in the poor colonizer C. jejuni NCTC 11168-PMSRU isolate. Variation in the amino acid sequences resulting in different isoelectric points and relative mobility of the flagellin and C. jejuni major outer membrane (MOMP) protein were also detected between the two isolates. Western blotting of the bacterial proteins revealed the presence of two flagellin proteins in the poor colonizer versus one in the robust colonizing isolate, but no differences in MOMP. These results demonstrate that proteomics is useful for characterizing phenotypic variation among Campylobacter spp. isolates. Interestingly, different gene products potentially involved in robust colonization of chickens by Campylobacter spp. appear to conform to recently identified expression patterns in biofilm or agar adapted isolates.