Molecular characterization of ‘Candidatus Borrelia tachyglossi’ (family Spirochaetaceae) in echidna ticks, Bothriocroton concolor

Recently, a novel species of the genus Borreliawas identified in Bothriocroton concolor and Ixodes holocyclus ticks from echidnas. Analyses of 16S rRNA and flaB genes identified three closely related genotypes of this bacterium (Borrelia sp. Aus A-C) that were unique and distinct from previously described borreliae. Phylogenetic analyses of flaB (763 bp), groEL (1537 bp), gyrB (1702 bp) and glpQ (874 bp) gene sequences and concatenated sequences (3585 bp) of three gene loci (16S rRNA, flaB and gyrB) were consistent with previous findings and confirm that this novel species of the genus Borrelia is more closely related to, yet distinct from, the Reptile-associated (REP) and Relapsing Fever (RF) groups. At the flaB locus, genotypes A, B and C shared the highest percentage sequence similarities (87.9, 88 and 87.9 %, respectively) with B.orrelia turcica (REP), whereas at the groEL and gyrB loci, these genotypes were most similar (88.2-89.4 %) to B.orrelia hermsii (RF). At the glpQ locus, genotypes A and B were most similar (85.7 and 85.4 % respectively) to Borrelia sp. Tortoise14H1 (REP). The presence of the glpQ gene, which is absent in the Lyme Borreliosis group spirochaetes, further emphasises that the novel species of the genus Borrelia characterized in the present study does not belong to this group. Phylogenetic analyses at multiple loci produced consistent topographies revealing the monophyletic grouping of this bacterium, therefore providing strong support for its species status. We propose the name 'CandidatusBorrelia tachyglossi', and hypothesize that this species of the genus Borrelia may be endemic to Australia. The pathogenic potential of this bacterium is not yet known.