mRNA transcript distribution bias between Borrelia burgdorferi bacteria and their outer membrane vesicles

Borrelia burgdorferi, a bacterium in the spirochete phylum, is the causative agent of Lyme disease. Borrelia burgdorferi has a linear chromosome with a number of circular and linear plasmids. Bacteria, including B. burgdorferi, release spherical outer membrane vesicles (OMVs) that are known to carry secretory products including metabolites, nucleic acids and proteins. Herein, we provide the first comparative transcriptomic analysis of the vesicles released from B. burgdorferi. We identified a total of ∼1200 unique transcripts with at least one mapped read from the bacterial cell and its OMVs. We compared the spectrum of transcripts between bacterial cell and its OMVs, and found a biased distribution based on the source of transcripts, i.e. plasmid-encoded transcripts are more likely to be enriched in the OMVs. We validated the distribution for some of the transcripts by qPCR. This analysis provides the first evidence that some of the B. burgdorferi transcripts are preferentially packaged in OMV, which further suggest that the bacteria might use its OMVs for bacteria-bacteria or bacteria-host communications. This report also suggests a possible involvement of Borrelia-derived OMVs in the development of Lyme disease in both early and post disease syndromes.