Identification of novel genes in the oral pathogen Campylobacter rectus

A poorly described bacterium, Campylobacter rectus, has been implicated as an etiological agent of periodontal disease. The aim of this study was to use a comparative genomics approach to identify genes that contribute to the lifestyle of C. rectus as an oral pathogen.

Suppressive subtractive hybridization was used to identify genes encoded by C. rectus ATCC 33238, but not present in the genome of a related Campylobacter species, Campylobacter jejuni ATCC 11168.

Suppressive subtractive hybridization identified 154 unique DNA sequences from the C. rectus genome. Ninety-two of the 154 clones were classified as C. rectus-specific, as they did not show significant sequence homology to genes identified in any strain of C. jejuni (blast E-value >1E-3). blast analysis predicted that the 92 C. rectus-specific gene fragments play a role in a variety of biological processes including signal transduction mechanisms (histidine kinase, response regulators, diguanylate cyclases, chemotaxis receptor) and potentially virulence (S-layer RTX and cysteine desulfhydrase). Further analysis of the C. rectus-specific clones showed that 10 genes had Campylobacter homologues that were only found in species that commonly reside within the oral cavity of humans and 10 other fragments shared homology only with non-campylobacter organisms.

These data provide the first substantial insights into the genomic content of C. rectus, a significant oral pathogen. The genes identified in this study are a valuable resource for initiating new research on the virulence of C. rectus during periodontitis.