Recently, a novel species of the genusBorreliawas identified inBothriocroton concolorandIxodes holocyclusticks from echidnas. Analyses of 16S rRNA andflaBgenes identified three closely related genotypes of this bacterium (Borreliasp. Aus A-C) that were unique and distinct from previously described borreliae. Phylogenetic analyses offlaB(763 bp),groEL(1537 bp),gyrB(1702 bp) andglpQ(874 bp) gene sequences and concatenated sequences (3585 bp) of three gene loci (16S rRNA,flaBandgyrB) were consistent with previous findings and confirm that this novel species of the genusBorreliais more closely related to, yet distinct from, the Reptile-associated (REP) and Relapsing Fever (RF) groups. At theflaBlocus, genotypes A, B and C shared the highest percentage sequence similarities (87.9, 88 and 87.9 %, respectively) withB.orrelia turcica(REP), whereas at thegroELandgyrBloci, these genotypes were most similar (88.2–89.4 %) toB.orrelia hermsii(RF). At theglpQlocus, genotypes A and B were most similar (85.7 and 85.4 % respectively) toBorreliasp. Tortoise14H1 (REP). The presence of theglpQgene, which is absent in the Lyme Borreliosis group spirochaetes, further emphasises that the novel species of the genusBorreliacharacterized 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 ‘CandidatusBorreliatachyglossi’, and hypothesize that this species of the genusBorreliamay be endemic to Australia. The pathogenic potential of this bacterium is not yet known.