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Tilly K, Bestor A, Rosa PA. Functional Equivalence of OspA and OspB, but Not OspC, in Tick Colonization by Borrelia burgdorferi. Infect Immun 2016; 84:1565-1573. [PMID: 26953324 PMCID: PMC4862709 DOI: 10.1128/iai.00063-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 02/26/2016] [Indexed: 01/21/2023] Open
Abstract
Borrelia burgdorferi, a Lyme disease agent, makes different major outer surface lipoproteins at different stages of its mouse-tick infectious cycle. Outer surface protein A (OspA) coats the spirochetes from the time they enter ticks until they are transmitted to a mammal. OspA is required for normal tick colonization and has been shown to bind a tick midgut protein, indicating that OspA may serve as a tick midgut adhesin. Tick colonization by spirochetes lacking OspA is increased when the infecting blood meal is derived from mice that do not produce antibody, indicating that OspA may protect the spirochetes from host antibody, which will not recognize tick-specific proteins such as OspA. To further study the importance of OspA during tick colonization, we constructed a form of B. burgdorferi in which the ospA open reading frame, on lp54, was replaced with the ospC gene or the ospB gene, encoding a mammal-specific or tick-specific lipoprotein, respectively. These fusions yielded a strain that produces OspC within a tick (from the fusion gene) and during early mammalian infection (from the normal ospC locus) and a strain that produces OspB in place of OspA within ticks. Here we show that the related, tick-specific protein OspB can fully substitute for OspA, whereas the unrelated, mammal-specific protein OspC cannot. These data were derived from three different methods of infecting ticks, and they confirm and extend previous studies indicating that OspA both protects spirochetes within ticks from mammalian antibody and serves an additional role during tick colonization.
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Affiliation(s)
- Kit Tilly
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, Montana, USA
| | - Aaron Bestor
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, Montana, USA
| | - Patricia A Rosa
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, Montana, USA
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Phosphoenolpyruvate Phosphotransferase System Components Modulate Gene Transcription and Virulence of Borrelia burgdorferi. Infect Immun 2015; 84:754-64. [PMID: 26712207 DOI: 10.1128/iai.00917-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 12/17/2015] [Indexed: 12/16/2022] Open
Abstract
The phosphoenolpyruvate phosphotransferase system (PEP-PTS) and adenylate cyclase (AC) IV (encoded by BB0723 [cyaB]) are well conserved in different species of Borrelia. However, the functional roles of PEP-PTS and AC in the infectious cycle of Borrelia have not been characterized previously. We examined 12 PEP-PTS transporter component mutants by needle inoculation of mice to assess their ability to cause mouse infection. Transposon mutants with mutations in the EIIBC components (ptsG) (BB0645, thought to be involved in glucose-specific transport) were unable to cause infection in mice, while all other tested PEP-PTS mutants retained infectivity. Infectivity was partially restored in an in trans-complemented strain of the ptsG mutant. While the ptsG mutant survived normally in unfed as well as fed ticks, it was unable to cause infection in mice by tick transmission, suggesting that the function of ptsG is essential to establish infection by either needle inoculation or tick transmission. In Gram-negative organisms, the regulatory effects of the PEP-PTS are mediated by adenylate cyclase and cyclic AMP (cAMP) levels. A recombinant protein encoded by B. burgdorferi BB0723 (a putative cyaB homolog) was shown to have adenylate cyclase activity in vitro; however, mutants with mutations in this gene were fully infectious in the tick-mouse infection cycle, indicating that its function is not required in this process. By transcriptome analysis, we demonstrated that the ptsG gene may directly or indirectly modulate gene expression of Borrelia burgdorferi. Overall, the PEP-PTS glucose transporter PtsG appears to play important roles in the pathogenesis of B. burgdorferi that extend beyond its transport functions.
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3
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Ouyang Z, Zhou J. BadR (BB0693) controls growth phase-dependent induction of rpoS and bosR in Borrelia burgdorferi via recognizing TAAAATAT motifs. Mol Microbiol 2015; 98:1147-67. [PMID: 26331438 DOI: 10.1111/mmi.13206] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2015] [Indexed: 12/15/2022]
Abstract
In Borrelia burgdorferi (Bb), the alternative sigma factor RpoS plays a central role during Bb's adaptation to ticks and mammals. Previous studies have demonstrated that RpoS is not expressed during the early stages of spirochetal growth or when Bb resides in ticks during the intermolt phase, but the molecular details of these events remain unknown. In the current study, biomagnetic bead separation of rpoS promoter-binding proteins, coupled with genetic inactivation, was employed to identify BadR (BB0693) as a negative regulator that controls growth phase-dependent induction of rpoS and bosR in Bb. When badR was inactivated, the expression of rpoS and bosR was induced only during the early stages of bacterial growth, but not during the stationary growth phase. Recombinant BadR bound to the promoter DNA of rpoS and the regulatory region upstream of bosR via AT-rich TAAAATAT motifs. Mutations in this motif markedly inhibited or abolished rBadR binding. These results suggest that BadR directly influences the expression of both rpoS and bosR in Bb. This newly recognized role for BadR to fine-tune the activation of the RpoN-RpoS pathway at strategic times in Bb's life cycle potentially represents another layer of gene control over σ(54)-dependent gene regulation.
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Affiliation(s)
- Zhiming Ouyang
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Jianli Zhou
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
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Shi Y, Dadhwal P, Li X, Liang FT. BosR functions as a repressor of the ospAB operon in Borrelia burgdorferi. PLoS One 2014; 9:e109307. [PMID: 25271631 PMCID: PMC4182837 DOI: 10.1371/journal.pone.0109307] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/10/2014] [Indexed: 11/19/2022] Open
Abstract
The Lyme disease spirochete, Borrelia burgdorferi, must abundantly produce outer surface lipoprotein A (OspA) in the tick vector but downregulate OspA in mammals in order to evade the immune system and maintain its natural enzootic cycle. Here, we show that BosR binds two regulatory elements of the ospAB operon and that increasing BosR expression leads to downregulation of OspA. Both regulatory sequences, cisI and cisII, showed strong BosR-binding and cisII bound much tighter than cisI. A promoterless bosR gene fused with an inducible promoter was introduced into an rpoS mutant and a wild-type strain to assess RpoS-independent and -dependent downregulation of OspA by BosR. With the induction of BosR expression, OspA expression was reduced more significantly in the RpoS-deficient than wild-type background, but not completely repressed. In the presence of constitutive expression of OspC, DbpA and DbpB, increasing BosR production resulted in complete repression of OspA in the RpoS mutant. Taken together, the study clearly demonstrated BosR serves as a repressor that binds both regulatory elements of the ospAB operon and shuts off expression.
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Affiliation(s)
- Yanlin Shi
- Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America
| | - Poonam Dadhwal
- Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America
| | - Xin Li
- Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio, United States of America
| | - Fang Ting Liang
- Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America
- * E-mail:
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Groshong AM, Blevins JS. Insights into the biology of Borrelia burgdorferi gained through the application of molecular genetics. ADVANCES IN APPLIED MICROBIOLOGY 2014; 86:41-143. [PMID: 24377854 DOI: 10.1016/b978-0-12-800262-9.00002-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Borrelia burgdorferi, the vector-borne bacterium that causes Lyme disease, was first identified in 1982. It is known that much of the pathology associated with Lyme borreliosis is due to the spirochete's ability to infect, colonize, disseminate, and survive within the vertebrate host. Early studies aimed at defining the biological contributions of individual genes during infection and transmission were hindered by the lack of adequate tools and techniques for molecular genetic analysis of the spirochete. The development of genetic manipulation techniques, paired with elucidation and annotation of the B. burgdorferi genome sequence, has led to major advancements in our understanding of the virulence factors and the molecular events associated with Lyme disease. Since the dawn of this genetic era of Lyme research, genes required for vector or host adaptation have garnered significant attention and highlighted the central role that these components play in the enzootic cycle of this pathogen. This chapter covers the progress made in the Borrelia field since the application of mutagenesis techniques and how they have allowed researchers to begin ascribing roles to individual genes. Understanding the complex process of adaptation and survival as the spirochete cycles between the tick vector and vertebrate host will lead to the development of more effective diagnostic tools as well as identification of novel therapeutic and vaccine targets. In this chapter, the Borrelia genes are presented in the context of their general biological roles in global gene regulation, motility, cell processes, immune evasion, and colonization/dissemination.
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Affiliation(s)
- Ashley M Groshong
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Jon S Blevins
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
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Dulebohn DP, Hayes BM, Rosa PA. Global repression of host-associated genes of the Lyme disease spirochete through post-transcriptional modulation of the alternative sigma factor RpoS. PLoS One 2014; 9:e93141. [PMID: 24671196 PMCID: PMC3966842 DOI: 10.1371/journal.pone.0093141] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 02/28/2014] [Indexed: 11/18/2022] Open
Abstract
Borrelia burgdorferi, the agent of Lyme disease, is a vector-borne pathogen that transits between Ixodes ticks and vertebrate hosts. During the natural infectious cycle, spirochetes must globally adjust their transcriptome to survive in these dissimilar environments. One way B. burgdorferi accomplishes this is through the use of alternative sigma factors to direct transcription of specific genes. RpoS, one of only three sigma factors in B. burgdorferi, controls expression of genes required during tick-transmission and infection of the mammalian host. How spirochetes switch between different sigma factors during the infectious cycle has remained elusive. Here we establish a role for a novel protein, BBD18, in the regulation of the virulence-associated sigma factor RpoS. Constitutive expression of BBD18 repressed transcription of RpoS-dependent genes to levels equivalent to those observed in an rpoS mutant. Consistent with the global loss of RpoS-dependent transcripts, we were unable to detect RpoS protein. However, constitutive expression of BBD18 did not diminish the amount of rpoS transcript, indicating post-transcriptional regulation of RpoS by BBD18. Interestingly, BBD18-mediated repression of RpoS is independent of both the rpoS promoter and the 5’ untranslated region, suggesting a mechanism of protein destabilization rather than translational control. We propose that BBD18 is a novel regulator of RpoS and its activity likely represents a first step in the transition from an RpoS-ON to an RpoS-OFF state, when spirochetes transition from the host to the tick vector.
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Affiliation(s)
- Daniel P. Dulebohn
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- * E-mail:
| | - Beth M. Hayes
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Patricia A. Rosa
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
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Earnhart CG, Rhodes DVL, Smith AA, Yang X, Tegels B, Carlyon JA, Pal U, Marconi RT. Assessment of the potential contribution of the highly conserved C-terminal motif (C10) of Borrelia burgdorferi outer surface protein C in transmission and infectivity. Pathog Dis 2014; 70:176-84. [PMID: 24376161 DOI: 10.1111/2049-632x.12119] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/03/2013] [Accepted: 12/03/2013] [Indexed: 11/26/2022] Open
Abstract
OspC is produced by all species of the Borrelia burgdorferi sensu lato complex and is required for infectivity in mammals. To test the hypothesis that the conserved C-terminal motif (C10) of OspC is required for function in vivo, a mutant B. burgdorferi strain (B31::ospCΔC10) was created in which ospC was replaced with an ospC gene lacking the C10 motif. The ability of the mutant to infect mice was investigated using tick transmission and needle inoculation. Infectivity was assessed by cultivation, qRT-PCR, and measurement of IgG antibody responses. B31::ospCΔC10 retained the ability to infect mice by both needle and tick challenge and was competent to survive in ticks after exposure to the blood meal. To determine whether recombinant OspC protein lacking the C-terminal 10 amino acid residues (rOspCΔC10) can bind plasminogen, the only known mammalian-derived ligand for OspC, binding analyses were performed. Deletion of the C10 motif resulted in a statistically significant decrease in plasminogen binding. Although deletion of the C10 motif influenced plasminogen binding, it can be concluded that the C10 motif is not required for OspC to carry out its critical in vivo functions in tick to mouse transmission.
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Affiliation(s)
- Christopher G Earnhart
- Department of Microbiology and Immunology, Medical College of Virginia at Virginia Commonwealth University, Richmond, VA, USA; Center for the Study of Biological Complexity, Medical College of Virginia at Virginia Commonwealth University, Richmond, VA, USA
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Troxell B, Yang XF. Metal-dependent gene regulation in the causative agent of Lyme disease. Front Cell Infect Microbiol 2013; 3:79. [PMID: 24298449 PMCID: PMC3828560 DOI: 10.3389/fcimb.2013.00079] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/29/2013] [Indexed: 11/13/2022] Open
Abstract
Borrelia burgdorferi (Bb) is the causative agent of Lyme disease transmitted to humans by ticks of the Ixodes spp. Bb is a unique bacterial pathogen because it does not require iron (Fe2+) for its metabolism. Bb encodes a ferritin-like Dps homolog called NapA (also called BicA), which can bind Fe or copper (Cu2+), and a manganese (Mn2+) transport protein, Borrelia metal transporter A (BmtA); both proteins are required for colonization of the tick vector, but BmtA is also required for the murine host. This demonstrates that Bb's metal homeostasis is a critical facet of the complex enzootic life cycle between the arthropod and murine hosts. Although metals are known to influence the expression of virulence determinants during infection, it is unknown how or if metals regulate virulence in Bb. Recent evidence demonstrates that Bb modulates the intracellular Mn2+ and zinc (Zn2+) content and, in turn, these metals regulate gene expression through influencing the Ferric Uptake Regulator (Fur) homolog Borrelia Oxidative Stress Regulator (BosR). This mini-review focuses on the burgeoning study of metal-dependent gene regulation within Bb.
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Affiliation(s)
- Bryan Troxell
- Department of Immunology and Microbiology, Indiana University School of Medicine Indianapolis, IN, USA
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Tilly K, Bestor A, Rosa PA. Lipoprotein succession in Borrelia burgdorferi: similar but distinct roles for OspC and VlsE at different stages of mammalian infection. Mol Microbiol 2013; 89:216-27. [PMID: 23692497 PMCID: PMC3713631 DOI: 10.1111/mmi.12271] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2013] [Indexed: 12/21/2022]
Abstract
Borrelia burgdorferi alternates between ticks and mammals, requiring variable gene expression and protein production to adapt to these diverse niches. These adaptations include shifting among the major outer surface lipoproteins OspA, OspC, and VlsE at different stages of the infectious cycle. We hypothesize that these proteins carry out a basic but essential function, and that OspC and VlsE fulfil this requirement during early and persistent stages of mammalian infection respectively. Previous work by other investigators suggested that several B. burgdorferi lipoproteins, including OspA and VlsE, could substitute for OspC at the initial stage of mouse infection, when OspC is transiently but absolutely required. In this study, we assessed whether vlsE and ospA could restore infectivity to an ospC mutant, and found that neither gene product effectively compensated for the absence of OspC during early infection. In contrast, we determined that OspC production was required by B. burgdorferi throughout SCID mouse infection if the vlsE gene were absent. Together, these results indicate that OspC can substitute for VlsE when antigenic variation is unnecessary, but that these two abundant lipoproteins are optimized for their related but specific roles during early and persistent mammalian infection by B. burgdorferi.
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Affiliation(s)
- Kit Tilly
- Laboratory of Zoonotic Pathogens, NIAID, NIH, Rocky Mountain Laboratories, Hamilton, MT 59840, USA.
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10
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Zückert WR. A call to order at the spirochaetal host-pathogen interface. Mol Microbiol 2013; 89:207-11. [PMID: 23750784 DOI: 10.1111/mmi.12286] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/03/2013] [Indexed: 12/28/2022]
Abstract
As the Lyme disease spirochaete Borrelia burgdorferi shuttles back and forth between arthropod vector and vertebrate host, it encounters vastly different and hostile environments. Major mechanisms contributing to the success of this pathogen throughout this complex transmission cycle are phase and antigenic variation of abundant and serotype-defining surface lipoproteins. These peripherally membrane-anchored virulence factors mediate niche-specific interactions with vector/host factors and protect the spirochaete from the perils of the mammalian immune response. In this issue of Molecular Microbiology, Tilly, Bestor and Rosa redefine the roles of two lipoproteins, OspC and VlsE, during mammalian infection. Using a variety of promoter fusions in combination with a sensitive in vivo 'use it or lose it' gene complementation assay, the authors demonstrate that proper sequential expression of OspC followed by VlsE indeed matters. A previously suggested general functional redundancy between these and other lipoproteins is shown to be limited and dependent on an immunodeficient experimental setting that is arguably of diminished ecological relevance. These data reinforce the notion that OspC plays a unique role during initial infection while the antigenically variant VlsE proteins allow for persistence in the mammalian host.
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Affiliation(s)
- Wolfram R Zückert
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas School of Medicine, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA.
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Bryksin AV, Tomova A, Godfrey HP, Cabello FC. BmpA is a surface-exposed outer-membrane protein of Borrelia burgdorferi. FEMS Microbiol Lett 2010; 309:77-83. [PMID: 20546313 PMCID: PMC2913681 DOI: 10.1111/j.1574-6968.2010.02020.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
BmpA is an immunodominant protein of Borrelia burgdorferi as well as an arthritogenic factor. Rabbit antirecombinant BmpA (rBmpA) antibodies were raised, characterized by assaying their cross reactivity with rBmpB, rBmpC and rBmpD, and then rendered monospecific by absorption with rBmpB. This monospecific reagent reacted only with rBmpA in dot immunobinding and detected a single 39 kDa, pI 5.0, spot on two-dimensional immunoblots. It was used to assess the BmpA cellular location. BmpA was present in both detergent-soluble and -insoluble fractions of Triton X-114 phase-partitioned borrelial cells, suggesting that it was a membrane lipoprotein. Immunoblots of proteinase K-treated intact and Triton X-100 permeabilized cells showed digestion of BmpA in intact cells, consistent with surface exposure. This exposure was confirmed by dual-label immunofluorescence microscopy of intact and permeabilized borrelial cells. Conservation and surface localization of BmpA in all B. burgdorferi sensu lato genospecies could point to its playing a key role in this organism's biology and pathobiology.
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Affiliation(s)
- Anton V. Bryksin
- Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595
| | - Alexandra Tomova
- Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595
| | - Henry P. Godfrey
- Department of Pathology, New York Medical College, Valhalla, New York 10595
| | - Felipe C. Cabello
- Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595
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12
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Xu Q, McShan K, Liang FT. Two regulatory elements required for enhancing ospA expression in Borrelia burgdorferi grown in vitro but repressing its expression during mammalian infection. MICROBIOLOGY-SGM 2010; 156:2194-2204. [PMID: 20395273 PMCID: PMC3068683 DOI: 10.1099/mic.0.036608-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
During cycling between the tick vector and a mammal, the Lyme disease spirochaete Borrelia burgdorferi must coordinate expression of outer-surface proteins (Osps) A and B to quickly respond to environmental changes. The pathogen abundantly produces OspA/B in the tick, but represses their expression during mammalian infection. This paper reports a regulatory structure, consisting of two sequences flanking the ospAB promoter, that is required for enhancing ospA expression in B. burgdorferi grown in vitro, but repressing its expression during murine infection. Deletion or replacement of either the upstream or downstream sequence of the ospAB promoter caused a significant decrease in ospA expression in vitro, but a dramatic increase during murine infection. Fusion of either sequence with the flaB reporter promoter led to increased expression of an ospA reporter gene in vitro, but a decrease in the murine host. Furthermore, simultaneous fusion of both sequences with the reporter promoter showed a synergistic effect in enhancing expression of the ospA reporter in vitro, but repressing its expression during murine infection. Taken together, the results demonstrate that the regulatory structure functions oppositely in the two different environments and potentially provides B. burgdorferi with a molecular mechanism to quickly adapt to the distinct environments during its enzootic life cycle.
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Affiliation(s)
- Qilong Xu
- Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Kristy McShan
- Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Fang Ting Liang
- Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
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13
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Overexpression of CsrA (BB0184) alters the morphology and antigen profiles of Borrelia burgdorferi. Infect Immun 2009; 77:5149-62. [PMID: 19737901 DOI: 10.1128/iai.00673-09] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Borrelia burgdorferi, the agent of Lyme disease, alters its gene expression in response to highly disparate environmental signals encountered in its hosts. Among the relatively few regulators of adaptive gene expression present in the borrelial genome is an open reading frame (ORF), BB0184, annotated as CsrA (carbon storage regulator A). CsrA, in several bacterial species, has been characterized as a small RNA binding protein that functions as a global regulator affecting mRNA stability or levels of translation of multiple ORFs. Consistent with known functions of CsrA, overexpression of CsrA from B. burgdorferi (CsrABb) in Escherichia coli resulted in reduced accumulation of glycogen. We determined that csrABb is part of the flgK motility operon and that the synthesis of CsrABb was increased when B. burgdorferi was propagated under fed-tick conditions. Overexpression of CsrABb in B. burgdorferi strain B31 (ML23, lp25-negative clonal isolate) resulted in a clone, designated ES25, which exhibited alterations in colony morphology and a significant reduction in the levels of FlaB. Several lipoproteins previously characterized as playing a role in infectivity were also altered in ES25. Real-time reverse transcription-PCR analysis of RNA revealed significant differences in the transcriptional levels of ospC in ES25, while there were no such differences in the levels of other transcripts, suggesting posttranscriptional regulation of expression of these latter genes. These observations indicate that CsrABb plays a role in the regulation of expression of pathophysiological determinants of B. burgdorferi, and further characterization of CsrABb will help in better understanding of the regulators of gene expression in B. burgdorferi.
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14
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Promnares K, Kumar M, Shroder DY, Zhang X, Anderson JF, Pal U. Borrelia burgdorferi small lipoprotein Lp6.6 is a member of multiple protein complexes in the outer membrane and facilitates pathogen transmission from ticks to mice. Mol Microbiol 2009; 74:112-125. [PMID: 19703109 PMCID: PMC2754595 DOI: 10.1111/j.1365-2958.2009.06853.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Borrelia burgdorferi lipoprotein Lp6.6 is a differentially produced spirochete antigen. An assessment of lp6.6 expression covering representative stages of the infectious cycle of spirochetes demonstrates that the gene is solely expressed during pathogen persistence in ticks. Deletion of lp6.6 in infectious B. burgdorferi did not influence in vitro growth, or its ability to persist and induce inflammation in mice, migrate to larval or nymphal ticks or survive through the larval-nymphal molt. However, Lp6.6-deficient spirochetes displayed significant impairment in their ability to transmit from infected ticks to naïve mice, which was restored upon genetic complementation of the mutant with a wild-type copy of lp6.6, establishing that Lp6.6 plays a role in pathogen transmission from ticks to mammals. Lp6.6 is a subsurface, yet highly abundant, outer membrane antigen. Two-dimensional blue native/SDS-PAGE coupled with liquid chromatography-mass spectrometry (LC-MS/MS) analysis and protein cross-linking studies independently shows that Lp6.6 exists in multiple protein complexes in the outer membrane. We speculate that the function of Lp6.6 is connected to the physiological processes of these membrane complexes. Further characterization of differentially produced membrane antigens and associated protein complexes will likely aid in our understanding of the molecular details of B. burgdorferi persistence and transmission through a complex enzootic cycle.
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Affiliation(s)
- Kamoltip Promnares
- Department of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA.Virginia-Maryland Regional College of Veterinary Medicine, College Park, MD 20742, USA.Department of Entomology, Connecticut Agricultural Experiment Station, New Haven, CT 06504, USA
| | - Manish Kumar
- Department of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA.Virginia-Maryland Regional College of Veterinary Medicine, College Park, MD 20742, USA.Department of Entomology, Connecticut Agricultural Experiment Station, New Haven, CT 06504, USA
| | - Deborah Y Shroder
- Department of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA.Virginia-Maryland Regional College of Veterinary Medicine, College Park, MD 20742, USA.Department of Entomology, Connecticut Agricultural Experiment Station, New Haven, CT 06504, USA
| | - Xinyue Zhang
- Department of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA.Virginia-Maryland Regional College of Veterinary Medicine, College Park, MD 20742, USA.Department of Entomology, Connecticut Agricultural Experiment Station, New Haven, CT 06504, USA
| | - John F Anderson
- Department of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA.Virginia-Maryland Regional College of Veterinary Medicine, College Park, MD 20742, USA.Department of Entomology, Connecticut Agricultural Experiment Station, New Haven, CT 06504, USA
| | - Utpal Pal
- Department of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA.Virginia-Maryland Regional College of Veterinary Medicine, College Park, MD 20742, USA.Department of Entomology, Connecticut Agricultural Experiment Station, New Haven, CT 06504, USA
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Common and unique contributions of decorin-binding proteins A and B to the overall virulence of Borrelia burgdorferi. PLoS One 2008; 3:e3340. [PMID: 18833332 PMCID: PMC2556102 DOI: 10.1371/journal.pone.0003340] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 09/12/2008] [Indexed: 11/19/2022] Open
Abstract
As an extracellular bacterium, the Lyme disease spirochete Borrelia burgdorferi resides primarily in the extracellular matrix and connective tissues and between host cells during mammalian infection, where decorin and glycosaminoglycans are abundantly found, so its interactions with these host ligands potentially affect various aspects of infection. Decorin-binding proteins (Dbps) A and B, encoded by a 2-gene operon, are outer surface lipoproteins with similar molecular weights and share approximately 40% identity, and both bind decorin and glycosaminoglycans. To investigate how DbpA and DbpB contribute differently to the overall virulence of B. burgdorferi, a dbpAB mutant was modified to overproduce the adhesins. Overproduction of either DbpA or DbpB resulted in restoration of the infectivity of the mutant to the control level, measured by 50% infectious dose (ID(50)), indicating that the two virulence factors are interchangeable in this regard. Overproduction of DbpA also allowed the mutant to disseminate to some but not all distal tissues slightly slower than the control, but the mutant with DbpB overproduction showed severely impaired dissemination to all tissues that were analyzed. The mutant with DbpA overproduction colonized all tissues, albeit generating bacterial loads significantly lower than the control in heart and joint, while the mutant overproducing DbpB remained severely defective in heart colonization and registered bacterial loads substantially lower than the control in joint. Taken together, the study indicated that DbpA and DbpB play a similar role in contribution to infectivity as measured by ID(50) value but contribute differently to dissemination and tissue colonization.
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