Borrelia maritima sp. nov., a novel species of the Borrelia burgdorferi sensu lato complex, occupying a basal position to North American species

Abstract

<i>Borrelia</i> species are vector-borne parasitic bacteria with unusual, highly fragmented genomes that include a linear chromosome and linear as well as circular plasmids that differ numerically between and within various species. Strain CA690^T, which was cultivated from a questing <i>Ixodes spinipalpis</i> nymph in the San Francisco Bay area, CA, was determined to be genetically distinct from all other described species belonging to the <i>Borrelia burgdorferi sensu lato</i> complex. The genome, including plasmids, was assembled using a hybrid assembly of short Illumina reads and long reads obtained via Oxford Nanopore Technology. We found that strain CA690^T has a main linear chromosome containing 902176 bp with a blast identity ≤91 % compared with other <i>Borrelia</i> species chromosomes and five linear and two circular plasmids. A phylogeny based on 37 single-copy genes of the main linear chromosome and rooted with the relapsing fever species <i>Borrelia duttonii</i> strain Ly revealed that strain CA690^T had a sister-group relationship with, and occupied a basal position to, species occurring in North America. We propose to name this species <i>Borrelia maritima</i> sp. nov. The type strain, CA690^T, has been deposited in two national culture collections, DSMZ (=107169) and ATCC (=TSD-160).