Identification of a Campylobacter coli methyltransferase targeting adenines at GATC sites

• Published in: FEMS microbiology letters Vol. 364; no. 7; p. fnw268
• Main Authors: Dutta, Vikrant, Altermann, Eric, Crespo, Maria D., Olson, Jonathan W., Siletzky, Robin M., Kathariou, Sophia
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-04-2017
• Subjects: Adaptation; Adenine; Adenine - metabolism; Animals; Campylobacter; Campylobacter coli; Campylobacter coli - enzymology; Campylobacter coli - genetics; Cattle; Chloramphenicol; Deoxyribonucleic acid; DNA; DNA Methylation; DNA methyltransferase; Genome, Bacterial; Genomes; Host preferences; Humans; Methylation; Methyltransferases - genetics; Methyltransferases - isolation & purification; Methyltransferases - metabolism; Microbiology; Nucleotide Motifs; Nucleotide sequence; Open Reading Frames; Sequence Analysis - methods; Site-specific DNA methyltransferase (adenine-specific); Swine; DNA methylation; GATC; MboI resistance; methyltransferase; C. coli; Campylobacter
• ISSN: 1574-6968; 0378-1097; 1574-6968
• DOI: 10.1093/femsle/fnw268

Abstract
Campylobacter coli can infect humans and colonize multiple other animals, but its host-associated genes or adaptations are poorly understood. Adenine methylation at GATC sites, resulting in MboI resistance of genomic DNA, was earlier frequently detected among C. coli from swine but not among turkey-derived isolates. The underlying genetic basis has remained unknown. Comparative genome sequence analyses of C. coli 6461, a swine-derived strain with MboI-resistant DNA, revealed two chromosomal ORFs, 0059 and 0060, encoding a putative DNA methyltransferase and a conserved hypothetical protein, respectively, which were lacking from the genome of the turkey-derived C. coli strain 11601, which had MboI-susceptible DNA. To determine whether ORF0059 mediated MboI resistance and hence encoded a putative N6-adenine DNA methyltransferase, the gene was cloned immediately upstream of a chloramphenicol resistance cassette (cat) and a PCR fragment harboring ORF0059-cat was transformed into C. coli 11601. The transformants had MboI-resistant DNA, suggesting a direct role of this gene in methylation of adenines at GATC sites. In silico analyses suggested that the ORF0059-ORF0060 cassette was more frequent among C. coli from swine than certain other sources (e.g. cattle, humans). Potential impacts of ORF0059-mediated methylation on C. coli host preference and other adaptations remain to be elucidated.
We identified a gene encoding a N6-adenine DNA methyltransferase in Campylobacter coli rendering DNA resistant to digestion by MboI, and described a predilection of this gene for C. coli from swine.