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item Meinersmann, Richard - Rick

Submitted to: Genome Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2003
Publication Date: 9/1/2003
Citation: Meinersmann, R.J., Dingle, K., Maiden, M. 2003. Genetic exchange among campylobacter species. Genome Letters. 2(1/2):8-52.

Interpretive Summary: Campylobacter jejuni is the leading bacterial cause of diarrheal disease in humans. The organism is highly variable, which makes it difficult to track in outbreaks and may give it advantages in establishing infections. This study was designed to look at DNA sequences from a large number of C. jejuni to see how patterns of sequence variability can be explained. It was already known that C. jejuni can exchange DNA from one strain to another within the species. This study showed that C. jejuni also exchanges DNA with other species. It also appears that the genes that may be involved in exchange are not restricted and that large portions of the genome may be exchanged in a single event. Unexpectedly, it appeared that strains of C. jejuni that were associated with chickens are less likely to have DNA from other species and strains from cattle and sheep are more likely to have foreign DNA. This knowledge will be useful in tracking strains of C. jejuni and also for recognizing features of the organism that give it an advantage in specific hosts.

Technical Abstract: Multilocus sequence typing (MLST) has been implemented for Campylobacter jejuni. At the time of this writing there have been identified 791 sequence types (STs). It has been shown that recombination probably occurs at a significant rate in all the analyzed loci. It will be shown here that all the loci also have disparate alleles with sequences that indicate either independent clonal evolution or recombination with more distant donors, i.e., donors from other species. Fifty-one STs had at least one disparate allele among the 7 loci in the database. One ST had disparate alleles at all seven loci and 16 STs had two to six disparate alleles. Mapping of the genomic location of the disparate alleles indicates that of the STs with multiple disparate alleles, 4 of these must have arisen in multiple events and the other 12 may have been single events, although linkage patterns suggest that many of these involved multiple events as well. The source of the isolates with disparate alleles showed segregation, chicken isolates were underrepresented and bovine and ovine isolates were overrepresented in this group. The source of the disparate alleles can not be presently identified, but the donor organisms must either be rare in chickens or there are barriers to recombination to C. jejuni from those donors in chicken-linked environments.