Proposing a type strain for Borrelia tillae, a relapsing fever species from South Africa

Ornithodoros zumpti is a soft tick species in eastern South Africa. In 1961, Zumpt and Organ described the transmission of a relapsing fever Borrelia species from O. zumpti to laboratory mice. The Borrelia species showed phenotypic differences to Borrelia duttonii and was designated Borrelia tillae Zumpt and Organ 1961 (Approved Lists 1980). At the German National Reference Center for Borrelia (NRZ), Oberschleissheim, a sample containing blood of an infected laboratory mouse labelled 'Borrelia tillae', was cultured. We sequenced PCR products of the 16S rRNA locus, flaB and MLST loci and generated whole-genome sequences using Pacific Biosciences technologies. The Borrelia 16S rRNA amplification product from DNA of an O. zumpti colony was sequenced and compared to the 16S rRNA gene sequence from the culture at the NRZ. No identical matches to 16S rRNA gene, flaB or MLST sequences were found in BLASTn searches of the NCBI nucleotide database. In phylogenies of those sequences, B. tillae sequences clustered on their own branches. However, borrelial 16S rRNA gene sequences from an O. zumpti colony were identical to the sequence obtained from the cultured isolate. The genome of B. tillae consists of a linear chromosome, 5 linear and 11 circular plasmids (including the megaplasmid). Sequence comparison provides evidence that the recovered isolate (named 'Krampitz') differs from all Borrelia spp. for which sequence data exist. Identical 16S rRNA gene sequences from an O. zumpti colony to the cultured isolate strongly support the notion that we recovered B. tillae. Because there was no type strain available for B. tillae, we propose strain 'Krampitz' to be recognized as the type strain for the species according to rule 18f of the International Code of Nomenclature of Prokaryotes. The type strain, Krampitz^T, has been deposited in two culture collections, DSMZ (=DSM 121361) and NCCB (=101126).