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Mol Microbiol. 2019 Nov 19. doi: 10.1111/mmi.14427. [Epub ahead of print]

Characterization of 6S RNA in the Lyme disease spirochete.

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Division of Biological Sciences, University of Montana, Missoula, MT, USA.
Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, USA.
School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA.
Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT, USA.


6S RNA binds to RNA polymerase and regulates gene expression, contributing to bacterial adaptation to environmental stresses. In this study, we examined the role of 6S RNA in murine infectivity and tick persistence of the Lyme disease spirochete Borrelia (Borreliella) burgdorferi. B. burgdorferi 6S RNA (Bb6S RNA) binds to RNA polymerase, is expressed independent of growth phase or nutrient stress in culture, and is processed by RNase Y. We found that rny (bb0504), the gene encoding RNase Y, is essential for B. burgdorferi growth, while ssrS, the gene encoding 6S RNA, is not essential, indicating a broader role for RNase Y activity in the spirochete. Bb6S RNA regulates expression of the ospC and dbpA genes encoding outer surface protein C and decorin binding protein A, respectively, which are lipoproteins important for host infection. The highest levels of Bb6S RNA are found when the spirochete resides in unfed nymphs. ssrS mutants lacking Bb6S RNA were compromised for infectivity by needle inoculation, but injected mice seroconverted, indicating an ability to activate the adaptive immune response. ssrS mutants were successfully acquired by larval ticks and persisted through fed nymphs. Bb6S RNA is one of the first regulatory RNAs identified in B. burgdorferi that controls the expression of lipoproteins involved in host infectivity.


6S RNA; Borrelia burgdorferi; Lyme disease; RNA; Spirochaetales; bacterial; gene expression regulation; small untranslated


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