Purpose: The objective of our study was to employ genome sequence information and functional genetic analyses in order to identify genomic attributes associated with animal host preference in C. jejuni and C. coli.
Methods: Total genomic DNA of one turkey-derived C. jejuni, two turkey-derived C. coli and one swine-derived C. coli was sequenced. Coding sequences were analyzed in terms of their presence in the different sequenced genomes using a novel functional genome distribution algorithm followed by a custom cluster comparison. Presence and comparative genomic location of homologous sequences in the different genomes was determined. A membrane macroarray-based hybridization format was used to assess host specificity of putative host-associated ORFs. Primers derived from these ORFs were used as probes to hybridize a panel of 20 strains of C. colifrom different animal hosts.
Results: Comparison of the two turkey-derived genomes revealed 387 and 83 ORFs unique to C. coli 11601 and 6067, respectively. Comparative analysis of ORFs conserved in the turkey-derived C. coli strains but absent from C. coli 6461 (swine) identified 17 putative turkey-associated candidates. Similarly, we identified 82 putative host-associated ORFs harbored by C. coli 6461 (swine) but absent from both of the turkey-derived genomes, including a putative DNA methyltransferase. Other sequences with potential for host association seem to be due to insertion events in the genome.
Significance: The genome sequence data suggest that the majority of strain-specific sequences in the two sequenced turkey-derived strains have a highly conserved homolog among other campylobacters, suggesting horizontal gene transfer among members of the Campylobacter pangenome.