Molecular Characterisation of a Type III Restriction-Modification System in Campylobacter Upsaliensis

AbstractTwo examples of Campylobacter upsaliensisRM3195 and JV21 strains are shown to carry putative type III restriction (res)-modification (mod)enzyme gene clusters, following genome sequence analyses. It is suggested that the cluster is composed of at least three structural genes, res,internal methylase gene and mod,in the strains, based on the nucleotide sequence information. A ribosome binding site, a putative promoter consisting of a consensus sequence at the-10-like structure and a semiconserved T-rich region and a putative intrinsic ρ-independent transcriptional terminator were identified for the gene cluster in the two strains. Using two primer pairs, f-/r-res and f-/r-mod, 34 of 41 C. upsaliensisisolates generated two expected amplicons of the resand modgene segments, and using another primer pair, the same number of isolates also generated an amplicon of the resand modgene segments cluster, including the third internal methylase gene. Thus, C. upsaliensisisolates frequently carried putative type III R-M gene clusters, encoding the three enzymes. Interestingly, two possible overlaps were identified within the three tandem structural genes. In addition, the type III R-M gene cluster loci appear to be very similar among the C. upsaliensisisolates and very different from other thermophilic campylobacters.