An lp17-encoded small non-coding RNA with a potential regulatory role in mammalian host adaptation by the Lyme disease spirochete

Abstract

The bacterial agent of Lyme disease, Borrelia burgdorferi, relies on an intricate gene regulatory network to transit between the disparate Ixodes tick vector and mammalian host environments. We recently reported that a B. burgdorferi mutant lacking an intergenic region of lp17 displayed attenuated murine tissue colonization and pathogenesis due to altered antigen expression. In this study, a more detailed characterization of the putative regulatory factor encoded by the region was pursued through genetic complementation of the mutant with variants of the intergenic sequence. In cis complemented strains featuring mutations aimed at eliminating potential BBD07 protein translation were capable of full tissue colonization, suggesting that the region encodes an sRNA. In trans complementation resulted in elevated transcription levels and was found to completely abolish infectivity in both immunocompetent and immunodeficient mice. Quantitative analysis of transcription of the putative sRNA by wild type B. burgdorferi showed it to be highly induced during murine infection. Lastly, targeted deletion of this region resulted in significant changes to the transcriptome, including genes with potential roles in transmission and host adaptation. The findings reported herein strongly suggest that this lp17 intergenic region encodes for an sRNA with a critical role in the gene regulation required for adaptation and persistence of the pathogen in the mammalian host.

Extensive diversity in RNA termination and regulation revealed by transcriptome mapping for the Lyme pathogenB. burgdorferi

“…sRNA annotations (Supplementary Table 2), as outlined above, were merged and sRNA gene names included for ssrA /tmRNA (SR0030), ssrS (6S) (SR0136) (Drecktrah et al, 2020), rnpB (SR0613), BsrW (SR0412) (Arnold et al, 2016), and IttA (SR0736) (Medina-Perez et al, 2020). The following sRNAs were missed from Supplementary Table 2 because of a lack of a 3′/5′ end within 75 nt of the previous sRNA annotations and were manually added: srp , ffs (4.5S) (SR0360), DsrA (SR0440) (Lybecker and Samuels, 2007) and IttB (Crowley and Bankhead, 2020). The ORF annotation for pncA ( bbe22 ) was updated to include the experimentally determined start codon (Jewett et al, 2011).…”