Comparative Genome Analysis of Canine Oral Treponemes

Abstract

Background: Treponeme bacteria play key roles in periodontal diseases in humans and dogs. Objectives To compare the genome biology of five canine oral ‘Treponema denticola-like’ isolates with human oral T. denticola isolates. Methods Genomic DNA was purified (Qiagen, QIAamp DNA Mini kits) from canine oral ‘Treponema denticola-like’ isolates cTd1, cTd2, cTd3, cTd4 and cTd5 (supplied by Dr. Chris Wyss), cultured anaerobically in TYGVS medium. Whole genome sequencing libraries were prepared and sequenced using both Illumina Hi-Seq and Oxford NANOPORE 1D minION platforms. Raw sequencing reads were trimmed and quality filtered. De novo assembly was performed using canu and pilon pipelines. The draft genomes were annotated using RASTv2. Results Genome assembly resulted in one contig for cTd2, cTd3 and cTd4, and two contigs for cTd1 and cTd5. The genome sizes of cTd1, cTd2, cTd3, cTd4 and cTd5 were 3.0 ± 0.11 Mb with a G+C content of 37.8 ± 0.11%. Preliminary annotation revealed that the average number of coding DNA sequences (CDSs) were 2847 ± 126 and each canine strain contained 2 copies of the 16S-23S-5S rRNA operon. The 5 canine ‘T. denticola-like’ strains shared >98.5% 16S rRNA gene similarity with human T. denticola strains; however, they shared <90% average genome similarity with human T. denticola strains. The major surface protein Msp from each canine strain shared less than 60% amino acid identity with that from T. denticola ATCC 35405 (TDE 0405). Homologues of the dentilisin (PrcAB-PrtP) operon were only identified in four canine strains (cTd2, cTd3, cTd4 and cTd5), and shared only 68 ± 6.5% average amino acid identity with those from ATCC 35405 (TDE 0760-0762). Homologues of the serine-dependent peptidase oligopeptidase B (OpdB) were identified in all five canine strains, which shared average amino acid similarities of 91 ± 0.4% with OpdB (TDE 2140) from ATCC 35405. Conclusion The canine oral ‘Treponema denticola-like’ isolates are notably distinct from human oral Treponema denticola strain lineages, but share homologues of several established virulence factors.