Novel small RNAs expressed by Bartonella bacilliformis under multiple conditions reveal potential mechanisms for persistence in the sand fly vector and human host.

Shaun Wachter,Michael F Minnick,Rahul Raghavan,Linda D Hicks,Joseph M Vinetz

doi:10.1371/journal.pntd.0008671

Shaun Wachter, Michael F Minnick + Show 3 more

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https://doi.org/10.1371/journal.pntd.0008671

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Abstract

Bartonella bacilliformis, the etiological agent of Carrión’s disease, is a Gram-negative, facultative intracellular alphaproteobacterium. Carrión’s disease is an emerging but neglected tropical illness endemic to Peru, Colombia, and Ecuador. B. bacilliformis is spread between humans through the bite of female phlebotomine sand flies. As a result, the pathogen encounters significant and repeated environmental shifts during its life cycle, including changes in pH and temperature. In most bacteria, small non-coding RNAs (sRNAs) serve as effectors that may post-transcriptionally regulate the stress response to such changes. However, sRNAs have not been characterized in B. bacilliformis, to date. We therefore performed total RNA-sequencing analyses on B. bacilliformis grown in vitro then shifted to one of ten distinct conditions that simulate various environments encountered by the pathogen during its life cycle. From this, we identified 160 sRNAs significantly expressed under at least one of the conditions tested. sRNAs included the highly-conserved tmRNA, 6S RNA, RNase P RNA component, SRP RNA component, ffH leader RNA, and the alphaproteobacterial sRNAs αr45 and speF leader RNA. In addition, 153 other potential sRNAs of unknown function were discovered. Northern blot analysis was used to confirm the expression of eight novel sRNAs. We also characterized a Bartonella bacilliformis group I intron (BbgpI) that disrupts an un-annotated tRNACCUArg gene and determined that the intron splices in vivo and self-splices in vitro. Furthermore, we demonstrated the molecular targeting of Bartonella bacilliformis small RNA 9 (BbsR9) to transcripts of the ftsH, nuoF, and gcvT genes, in vitro.

Highlights

Bartonella bacilliformis is a Gram-negative, facultative intracellular bacterium and the etiological agent of Carrion’s disease in humans
Bacteria often express small non-coding RNAs (sRNAs) to fine-tune the production of proteins involved in a wide array of biological processes
Peaks were found in intergenic regions (IGRs), antisense to annotated genes or as leader RNAs in 5’ untranslated regions (UTRs) of annotated genes

Summary

Introduction

Bartonella bacilliformis is a Gram-negative, facultative intracellular bacterium and the etiological agent of Carrion’s disease in humans. The initial, acute stage of Carrion’s disease is referred to as Oroya fever (OF), and it is characterized by colonization of the entire circulatory system, leading to infection of ~61% of all circulating erythrocytes [7,8]. This bacterial burden typically leads to severe anemia, fever, jaundice, and hepatomegaly, among other symptoms [9]. Weeks or months following OF, B. bacilliformis seemingly invades endothelial cells, where it triggers cell proliferation and angiogenesis This event leads to formation of blood-filled blisters of the skin, referred to as verruga peruana (VP). In consideration of reports involving less virulent B. bacilliformis strains and the possibility that other Bartonella spp. can cause mild symptoms resembling Carrion’s disease, the incidence of the disease is likely underreported [11,12,13]

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