title: Rrp2, a prokaryotic enhancer-like binding protein, is essential for viability of Borrelia burgdorferi.
abstract: The Lyme disease spirochete, Borrelia burgdorferi, exists in two diverse niches (i.e., an arthropod tick vector and mammalian host) during its enzootic life cycle. To effectively adapt to these unique environments, the bacterium alters the expression of numerous genes, including several major outer surface (lipo)proteins that are required for infection and transmission. An enhancer-binding protein (EBP), known as Rrp2, is one identified activator of the RpoN/RpoS alternative sigma factor cascade. Because initial efforts to generate an rrp2 deletion strain were unsuccessful, the role of Rrp2 in the activation of the RpoN/RpoS pathway was first defined using a strain of B. burgdorferi carrying an rrp2 point mutant that was defective in its ability to activate RpoN-dependent transcription. The fact that subsequent attempts to disrupt rrp2 have also been unsuccessful has led investigators to hypothesize that Rrp2 has other undefined functions which are essential for B. burgdorferi survival and independent of its EBP function. We used a lac-based inducible expression system to generate a conditional rrp2 mutant in virulent B. burgdorferi. In this strain, an isopropyl-β-D-thiogalactopyranoside-inducible copy of the rrp2 gene is expressed in trans from a borrelial shuttle vector. We found that the chromosomal copy of rrp2 could be inactivated only when rrp2 was induced, and the maintenance of rrp2 expression was required for the growth of the mutants. In addition, the overexpression of rrp2 is detrimental to B. burgdorferi growth in a manner that is independent of the RpoN/RpoS pathway. These studies provide the first direct evidence that rrp2 is an essential gene in B. burgdorferi.
authors.affiliation: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Groshong
authors.forename: Nora E
authors.initials: NE
authors.lastname: Gibbons
authors.forename: X Frank
authors.initials: XF
authors.lastname: Yang
authors.forename: Jon S
authors.initials: JS
authors.lastname: Blevins
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D025065:Borrelia burgdorferi / Q000235:genetics / Q000254:growth & development*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D020043:Genes, Essential; D050296:Microbial Viability; D009154:Mutation; D051877:RNA Polymerase Sigma 54 / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D051877:RNA Polymerase Sigma 54