New research explores the genetics of the bacteria responsible for Lyme disease in Canada

New research explores the genetic composition of Borrelia burgdorferi, the bacteria responsible for Lyme disease, specifically focusing on strains found in Canada. Lyme disease is a growing public health concern in Canada as the ticks that carry the bacteria spread northward due to climate change.¹

Little is currently known about the genetic characteristics and evolutionary history of Canadian B. burgdorferi strains. This lack of information makes it harder to understand how the pathogen originated and adapted to its new environment.

By generating the first complete genome sequences of six Canadian B. burgdorferi strains, their study offers valuable genetic data. These resources will help us and others track the origins and evolution of Lyme disease in Canada, which can inform public health strategies and disease management. 

Reconstructing these genomes is difficult because Borrelia genomes have variable content and structure, even within the same species or strain. This rapid evolution makes it challenging to use existing reference genomes for assembly. This study presents a hybrid approach to ensure the sequence and structure of the genomes are generated accurately.

The study successfully sequenced and assembled the complete genomes (including both the main chromosome and smaller DNA structures called plasmids) of six Canadian B. burgdorferi strains. They then compared these to other Borrelia genomes from the USA and Europe.

The overall structures of the Canadian Borrelia genomes were similar to other B. burgdorferi strains globally. However, they found differences in the content and structure of their plasmids.

Borrelia species have complex genomes with a main linear chromosome and many smaller linear and circular plasmids. These plasmids are highly variable in number and identity, even among strains of the same species. This variability in plasmid content means that the genes they carry can also differ between strains. 
This project has yielded an effective strategy for the comprehensive characterization of Borrelia. Ongoing efforts in the G. Magnotta Lab to isolate more Borrelia strains from large numbers of Canadian ticks will fuel this pipeline and enable deeper insights into the origins and diversity of these pathogens. A key focus of the G. Magnotta Lab is the clinical implications of pathogen biology. New, sequenced isolates will therefore be used in experiments to evaluate novel diagnostic test designs.

1. Read the full open access journal article, “Unravelling the genomic landscape of Canadian Borrelia burgdorferi: a comparison across global strains”. Read more: “A genomic perspective on Lyme disease in Canada”.