Large-Scale Sequencing of Borreliaceae for the Construction of Pan-Genomic-Based Diagnostics

Abstract

The acceleration of climate change has been associated with an alarming increase in the prevalence and geographic range of tick-borne diseases (TBD), many of which have severe and long-lasting effects-particularly when treatment is delayed principally due to inadequate diagnostics and lack of physician suspicion. Moreover, there is a paucity of treatment options for many TBDs that are complicated by diagnostic limitations for correctly identifying the offending pathogens. This review will focus on the biology, disease pathology, and detection methodologies used for the Borreliaceae family which includes the Lyme disease agent Borreliella burgdorferi. Previous work revealed that Borreliaceae genomes differ from most bacteria in that they are composed of large numbers of replicons, both linear and circular, with the main chromosome being the linear with telomeric-like termini. While these findings are novel, additional gene-specific analyses of each class of these multiple replicons are needed to better understand their respective roles in metabolism and pathogenesis of these enigmatic spirochetes. Historically, such studies were challenging due to a dearth of both analytic tools and a sufficient number of high-fidelity genomes among the various taxa within this family as a whole to provide for discriminative and functional genomic studies. Recent advances in long-read whole-genome sequencing, comparative genomics, and machine-learning have provided the tools to better understand the fundamental biology and phylogeny of these genomically-complex pathogens while also providing the data for the development of improved diagnostics and therapeutics.

Keywords: Lyme disease; borrelia; diagnostics; distributed genome hypothesis; pangenomics; tick-borne diseases.

Figure 1

The anatomy of the adult I. scapularis hard tick underneath a dissection microscope. The red arrows indicate the different anatomical parts of the I. scapularis.

Figure 2

Transmission and acquisition of Borreliellal spirochetes. The image was created in BioRender by KM Socarras 2022.

Figure 3

Dark field microscopic images of wet mount Borrelial spirochaetes (Borrelia hermsii strain DAH). Blood from C3H-Hej mice infected with B. hermsii was diluted 4-fold with phosphate buffered saline. (A): 100×, (B,C): 400×.