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Richards CL, Bontemps-Gallo S, Bourret TJ. Editorial: Host-pathogen interactions: the metabolic crossroads. Front Cell Infect Microbiol 2023; 13:1212051. [PMID: 37260702 PMCID: PMC10227595 DOI: 10.3389/fcimb.2023.1212051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 05/02/2023] [Indexed: 06/02/2023] Open
Affiliation(s)
- Crystal L. Richards
- Laboratory of Bacteriology, Division of Intramural Research, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, United States
| | - Sébastien Bontemps-Gallo
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019 - UMR 9017 - CIIL - Center for Infection and Immunity of Lille, Lille, France
| | - Travis J. Bourret
- Department of Medical Microbiology and Immunology, Creighton University School of Medicine, Omaha, NE, United States
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Hamik J, Bourret TJ, Smith H, Herman M, Birn R, Dawdy T, Zuffante MJ, Donahue MA. Detection of Borrelia burgdorferi infected Ixodes scapularis (Acari: Ixodidae) associated with local Lyme disease transmission in Nebraska, USA, 2021. Zoonoses Public Health 2023; 70:361-364. [PMID: 36785942 DOI: 10.1111/zph.13031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/09/2023] [Accepted: 01/30/2023] [Indexed: 02/15/2023]
Abstract
In August 2021, the Nebraska Department of Health and Human Services was notified by a local public health department of a cluster of two Lyme disease cases in patients with local exposure to wooded areas in a county located in their jurisdiction. Epidemiological investigations revealed that the two patients had similar symptom onset dates and had likely exposure to ticks at wooded sites located directly adjacent to one another. Two environmental investigations were completed in October 2021 and consisted of tick surveys at the patients' reported sites of tick exposure. 12 ticks were collected across the two surveys and identified the black-legged tick (Ixodes scapularis). During subsequent testing of the collected ticks, spirochete bacteria were isolated, cultured and confirmed as Borrelia burgdorferi sensu stricto by PCR. In total, 7 of 12 (58.3%) I. scapularis ticks tested positive for B. burgdorferi s.s. The results of this study document the fourth known established population of I. scapularis in Nebraska and confirms the first detection of B. burgdorferi s.s. in field collected ticks from Nebraska. The epidemiological and environmental investigation data provide the first evidence for local Lyme disease transmission occurring within Nebraska. These findings highlight the need for continued surveillance of I. scapularis and its associated pathogens in Nebraska to further characterize human risk and monitor emergence into other areas of the state.
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Affiliation(s)
- Jeff Hamik
- Nebraska Department of Health and Human Services, Lincoln, Nebraska, USA.,University of Nebraska, Lincoln, Nebraska, USA
| | | | - Halie Smith
- Nebraska Department of Health and Human Services, Lincoln, Nebraska, USA
| | - Molly Herman
- Northeast Nebraska Public Health Department, Wayne, Nebraska, USA
| | - Rachael Birn
- Nebraska Department of Health and Human Services, Lincoln, Nebraska, USA
| | - Tammy Dawdy
- Nebraska Department of Health and Human Services, Lincoln, Nebraska, USA
| | - Mona J Zuffante
- Winnebago Public Health Department, Winnebago, Nebraska, USA
| | - Matthew A Donahue
- Nebraska Department of Health and Human Services, Lincoln, Nebraska, USA
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Boyle WK, Sorensen HN, Bourret TJ. Essential Components of <em>Borreliella</em> (<em>Borrelia</em>) <em>burgdorferi In Vitro</em> Transcription Assays. J Vis Exp 2022. [DOI: 10.3791/64134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
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Boyle WK, Richards CL, Dulebohn DP, Zalud AK, Shaw JA, Lovas S, Gherardini FC, Bourret TJ. DksA-dependent regulation of RpoS contributes to Borrelia burgdorferi tick-borne transmission and mammalian infectivity. PLoS Pathog 2021; 17:e1009072. [PMID: 33600418 PMCID: PMC7924775 DOI: 10.1371/journal.ppat.1009072] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 03/02/2021] [Accepted: 02/03/2021] [Indexed: 12/14/2022] Open
Abstract
Throughout its enzootic cycle, the Lyme disease spirochete Borreliella (Borrelia) burgdorferi, senses and responds to changes in its environment using a small repertoire of transcription factors that coordinate the expression of genes required for infection of Ixodes ticks and various mammalian hosts. Among these transcription factors, the DnaK suppressor protein (DksA) plays a pivotal role in regulating gene expression in B. burgdorferi during periods of nutrient limitation and is required for mammalian infectivity. In many pathogenic bacteria, the gene regulatory activity of DksA, along with the alarmone guanosine penta- and tetra-phosphate ((p)ppGpp), coordinate the stringent response to various environmental stresses, including nutrient limitation. In this study, we sought to characterize the role of DksA in regulating the transcriptional activity of RNA polymerase and its role in the regulation of RpoS-dependent gene expression required for B. burgdorferi infectivity. Using in vitro transcription assays, we observed recombinant DksA inhibits RpoD-dependent transcription by B. burgdorferi RNA polymerase independent of ppGpp. Additionally, we determined the pH-inducible expression of RpoS-dependent genes relies on DksA, but this relationship is independent of (p)ppGpp produced by Relbbu. Subsequent transcriptomic and western blot assays indicate DksA regulates the expression of BBD18, a protein previously implicated in the post-transcriptional regulation of RpoS. Moreover, we observed DksA was required for infection of mice following intraperitoneal inoculation or for transmission of B. burgdorferi by Ixodes scapularis nymphs. Together, these data suggest DksA plays a central role in coordinating transcriptional responses in B. burgdorferi required for infectivity through DksA’s interactions with RNA polymerase and post-transcriptional control of RpoS. Lyme disease, caused by the spirochete bacteria Borreliella (Borrelia) burgdorferi, is the most common vector-borne illness in North America. The ability of B. burgdorferi to establish infection is predicated by its ability to coordinate the expression of virulence factors in response to diverse environmental stimuli encountered within Ixodes ticks and mammalian hosts. Previous studies have shown an essential role for the alternative sigma factor RpoS in regulating the expression of genes required for the successful transmission of B. burgdorferi by Ixodes ticks and infection of mammalian hosts. The DnaK suppressor protein (DksA) is a global gene regulator in B. burgdorferi that contributes to the expression of RpoS-dependent genes. In this study, using in vitro transcription assays, we determined DksA exerts its gene regulatory function through direct interactions with the B. burgdorferi RNA polymerase and controls the expression of RpoS-dependent genes required for mammalian infection by post-transcriptionally regulating cellular levels of RpoS. Our results demonstrate the utility of in vitro transcription assays to determine how gene regulatory proteins like DksA control gene expression in B. burgdorferi and reveal a novel role for DksA in the infectious cycle of B. burgdorferi.
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Affiliation(s)
- William K. Boyle
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska, United States of America
| | - Crystal L. Richards
- Laboratory of Bacteriology, Gene Regulation Section, Division of Intramural Research, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Daniel P. Dulebohn
- Laboratory of Bacteriology, Gene Regulation Section, Division of Intramural Research, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Amanda K. Zalud
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska, United States of America
| | - Jeff A. Shaw
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska, United States of America
| | - Sándor Lovas
- Department of Biomedical Sciences, Creighton University, Omaha, Nebraska, United States of America
| | - Frank C. Gherardini
- Laboratory of Bacteriology, Gene Regulation Section, Division of Intramural Research, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Travis J. Bourret
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska, United States of America
- * E-mail:
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Samuels DS, Lybecker MC, Yang XF, Ouyang Z, Bourret TJ, Boyle WK, Stevenson B, Drecktrah D, Caimano MJ. Gene Regulation and Transcriptomics. Curr Issues Mol Biol 2020; 42:223-266. [PMID: 33300497 DOI: 10.21775/cimb.042.223] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Borrelia (Borreliella) burgdorferi, along with closely related species, is the etiologic agent of Lyme disease. The spirochete subsists in an enzootic cycle that encompasses acquisition from a vertebrate host to a tick vector and transmission from a tick vector to a vertebrate host. To adapt to its environment and persist in each phase of its enzootic cycle, B. burgdorferi wields three systems to regulate the expression of genes: the RpoN-RpoS alternative sigma factor cascade, the Hk1/Rrp1 two-component system and its product c-di-GMP, and the stringent response mediated by RelBbu and DksA. These regulatory systems respond to enzootic phase-specific signals and are controlled or fine- tuned by transcription factors, including BosR and BadR, as well as small RNAs, including DsrABb and Bb6S RNA. In addition, several other DNA-binding and RNA-binding proteins have been identified, although their functions have not all been defined. Global changes in gene expression revealed by high-throughput transcriptomic studies have elucidated various regulons, albeit technical obstacles have mostly limited this experimental approach to cultivated spirochetes. Regardless, we know that the spirochete, which carries a relatively small genome, regulates the expression of a considerable number of genes required for the transitions between the tick vector and the vertebrate host as well as the adaptation to each.
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Affiliation(s)
- D Scott Samuels
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Meghan C Lybecker
- Department of Biology, University of Colorado, Colorado Springs, CO 80918, USA
| | - X Frank Yang
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Zhiming Ouyang
- Department of Molecular Medicine, University of South Florida, Tampa, FL 33612, USA
| | - Travis J Bourret
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE, 68105 USA
| | - William K Boyle
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE, 68105 USA
| | - Brian Stevenson
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky School of Medicine, Lexington, KY 40536, USA
| | - Dan Drecktrah
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Melissa J Caimano
- Departments of Medicine, Pediatrics, and Molecular Biology and Biophysics, UConn Health, Farmington, CT, USA
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Luedtke BE, Shaffer JJ, Monrroy E, Willicott CW, Bourret TJ. Molecular Detection of Spotted Fever Group Rickettsiae (Rickettsiales: Rickettsiaceae) in Dermacentor variabilis (Acari: Ixodidae) Collected Along the Platte River in South Central Nebraska. J Med Entomol 2020; 57:519-523. [PMID: 31576408 PMCID: PMC7530562 DOI: 10.1093/jme/tjz167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Indexed: 05/03/2023]
Abstract
Dermacentor variabilis is the predominant tick species in Nebraska and is presumed to be the primary vector of Rickettsia rickettsii associated with cases of Rocky Mountain spotted fever (RMSF). Interestingly, RMSF cases in Nebraska have increased on a year-to-year basis, yet the prevalence of R. rickettsii in D. variabilis ticks has not been established for Nebraska. Here we sought to set a baseline for the prevalence of R. rickettsii and other spotted fever group (SFG) rickettsiae harbored by D. variabilis ticks. Over a 3-yr period, D. variabilis were collected along the Platte River in south central Nebraska. Individual tick DNA was analyzed using endpoint PCR to identify ticks carrying SFG rickettsiae. In total, 927 D. variabilis were analyzed by PCR and 38 (4.1%) ticks tested positive for SFG rickettsiae. Presumptive positives were sequenced to identify the Rickettsia species, of which 29 (76%) were R. montanensis, 5 (13%) were R. amblyommatis, 4 (11%) were R. bellii, and R. rickettsii was not detected. These data indicate that R. rickettsii is likely at a low prevalence in south central Nebraska and spillover of R. amblyommatis into D. variabilis is likely occurring due to the invasive lone star tick (Amblyomma americanum). In addition, our data suggest that R. montanensis and R. amblyommatis could be associated with the increase in SFG rickettsiae infections in Nebraska. This information will be of value to clinicians and the general public for evaluating diagnosis of disease- and risk-associated environmental exposure, respectively.
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Affiliation(s)
| | - Julie J Shaffer
- Biology Department, University of Nebraska at Kearney, Kearney, NE
| | - Estrella Monrroy
- Biology Department, University of Nebraska at Kearney, Kearney, NE
| | | | - Travis J Bourret
- Department of Medical Microbiology and Immunology, Creighton University School of Medicine, Omaha, NE
- Corresponding author, e-mail:
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Jackson-Litteken CD, Zalud AK, Ratliff CT, Latham JI, Bourret TJ, Lopez JE, Blevins JS. Assessing the Contribution of an HtrA Family Serine Protease During Borrelia turicatae Mammalian Infection. Front Cell Infect Microbiol 2019; 9:290. [PMID: 31456953 PMCID: PMC6700303 DOI: 10.3389/fcimb.2019.00290] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 07/26/2019] [Indexed: 12/31/2022] Open
Abstract
Tick-borne relapsing fever (TBRF), characterized by recurring febrile episodes, is globally distributed and among the most common bacterial infections in some African countries. Despite the public health concern that this disease represents, little is known regarding the virulence determinants required by TBRF Borrelia during infection. Because the chromosomes of TBRF Borrelia show extensive colinearity with those of Lyme disease (LD) Borrelia, the exceptions represent unique genes encoding proteins that are potentially essential to the disparate enzootic cycles of these two groups of spirochetes. One such exception is a gene encoding an HtrA family protease, BtpA, that is present in TBRF Borrelia, but not in LD spirochetes. Previous work suggested that btpA orthologs may be important for resistance to stresses faced during mammalian infection. Herein, proteomic analyses of the TBRF spirochete, Borrelia turicatae, demonstrated that BtpA, as well as proteins encoded by adjacent genes in the B. turicatae genome, were produced in response to culture at mammalian body temperature, suggesting a role in mammalian infection. Further, transcriptional analyses revealed that btpA was expressed with the genes immediately upstream and downstream as part of an operon. To directly assess if btpA is involved in resistance to environmental stresses, btpA deletion mutants were generated. btpA mutants demonstrated no growth defect in response to heat shock, but were more sensitive to oxidative stress produced by t-butyl peroxide compared to wild-type B. turicatae. Finally, btpA mutants were fully infectious in a murine relapsing fever (RF) infection model. These results indicate that BtpA is either not required for mammalian infection, or that compensatory mechanisms exist in TBRF spirochetes to combat environmental stresses encountered during mammalian infection in the absence of BtpA.
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Affiliation(s)
- Clay D. Jackson-Litteken
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Amanda K. Zalud
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE, United States
| | - C. Tyler Ratliff
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Jacob I. Latham
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Travis J. Bourret
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE, United States
| | - Job E. Lopez
- Section of Tropical Medicine, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, United States
| | - Jon S. Blevins
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, United States,*Correspondence: Jon S. Blevins
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Shaw JA, Bourret TJ. Digital PCR-based Competitive Index for High-throughput Analysis of Fitness in Salmonella. J Vis Exp 2019. [PMID: 31132072 DOI: 10.3791/59630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
A competitive index is a common method used to assess bacterial fitness and/or virulence. The utility of this approach is exemplified by its ease to perform and its ability to standardize the fitness of many strains to a wild-type organism. The technique is limited, however, by available phenotypic markers and the number of strains that can be assessed simultaneously, creating the need for a great number of replicate experiments. Concurrent with large numbers of experiments, the labor and material costs for quantifying bacteria based on phenotypic markers are not insignificant. To overcome these negative aspects while retaining the positive aspects, we have developed a molecular-based approach to directly quantify microorganisms after engineering genetic markers onto bacterial chromosomes. Unique, 25 base pair DNA barcodes were inserted at an innocuous locus on the chromosome of wild-type and mutant strains of Salmonella. In vitro competition experiments were performed using inocula consisting of pooled strains. Following the competition, the absolute numbers of each strain were quantified using digital PCR and the competitive indices for each strain were calculated from those values. Our data indicate that this approach to quantifying Salmonella is extremely sensitive, accurate, and precise for detecting both highly abundant (high fitness) and rare (low fitness) microorganisms. Additionally, this technique is easily adaptable to nearly any organism with chromosomes capable of modification, as well as to various experimental designs that require absolute quantification of microorganisms.
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Affiliation(s)
- Jeff A Shaw
- Department of Medical Microbiology and Immunology, Creighton University School of Medicine
| | - Travis J Bourret
- Department of Medical Microbiology and Immunology, Creighton University School of Medicine;
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Bourret TJ, Boyle WK, Zalud AK, Valenzuela JG, Oliveira F, Lopez JE. The relapsing fever spirochete Borrelia turicatae persists in the highly oxidative environment of its soft-bodied tick vector. Cell Microbiol 2019; 21:e12987. [PMID: 30489694 PMCID: PMC6454574 DOI: 10.1111/cmi.12987] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 11/20/2018] [Accepted: 11/25/2018] [Indexed: 12/17/2022]
Abstract
The relapsing fever spirochete Borrelia turicatae possesses a complex life cycle in its soft-bodied tick vector, Ornithodoros turicata. Spirochetes enter the tick midgut during a blood meal, and, during the following weeks, spirochetes disseminate throughout O. turicata. A population persists in the salivary glands allowing for rapid transmission to the mammalian hosts during tick feeding. Little is known about the physiological environment within the salivary glands acini in which B. turicatae persists. In this study, we examined the salivary gland transcriptome of O. turicata ticks and detected the expression of 57 genes involved in oxidant metabolism or antioxidant defences. We confirmed the expression of five of the most highly expressed genes, including glutathione peroxidase (gpx), thioredoxin peroxidase (tpx), manganese superoxide dismutase (sod-1), copper-zinc superoxide dismutase (sod-2), and catalase (cat) by reverse-transcriptase droplet digital polymerase chain reaction (RT-ddPCR). We also found distinct differences in the expression of these genes when comparing the salivary glands and midguts of unfed O. turicata ticks. Our results indicate that the salivary glands of unfed O. turicata nymphs are highly oxidative environments where reactive oxygen species (ROS) predominate, whereas midgut tissues comprise a primarily nitrosative environment where nitric oxide synthase is highly expressed. Additionally, B. turicatae was found to be hyperresistant to ROS compared with the Lyme disease spirochete Borrelia burgdorferi, suggesting it is uniquely adapted to the highly oxidative environment of O. turicata salivary gland acini.
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Affiliation(s)
- Travis J Bourret
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska
| | - William K Boyle
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska
| | - Amanda K Zalud
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska
| | - Jesus G Valenzuela
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland
| | - Fabiano Oliveira
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland
| | - Job E Lopez
- Departments of Pediatrics and Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
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Shaw JA, Henard CA, Liu L, Dieckman LM, Vázquez-Torres A, Bourret TJ. Salmonella enterica serovar Typhimurium has three transketolase enzymes contributing to the pentose phosphate pathway. J Biol Chem 2018; 293:11271-11282. [PMID: 29848552 DOI: 10.1074/jbc.ra118.003661] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 05/23/2018] [Indexed: 11/06/2022] Open
Abstract
The genus Salmonella is responsible for many illnesses in humans and other vertebrate animals. We report here that Salmonella enterica serovar Typhimurium harbors three transketolases that support the non-oxidative branch of the pentose phosphate pathway. BLAST analysis identified two genes, STM14_2885 and STM14_2886, that together encode a putative transketolase (TktC) with 46-47% similarity to the known TktA and TktB isoforms. Assessing the mRNA and protein expression for each of the three transketolases, we determined that all are expressed in WT cells and regulated to varying extents by the alternative sigma factor RpoS. Enzyme assays with lysates from WT and transketolase-knockout strains established that TktA is responsible for >88% of the transketolase activity in WT cells. We purified recombinant forms of each isoenzyme to assess the kinetics for canonical transketolase reactions. TktA and TktB had comparable values for Vmax (539-1362 μm NADH consumed/s), Km (80-739 μm), and catalytic efficiency (1.02 × 108-1.06 × 109 m-1/s) for each substrate tested. The recombinant form of TktC had lower Km values (23-120 μm), whereas the Vmax (7.8-16 μm NADH consumed/s) and catalytic efficiency (5.58 × 106 to 6.07 × 108 m-1/s) were 10-100-fold lower. Using a murine model of Salmonella infection, we showed that a strain lacking all three transketolases is avirulent in C57BL/6 mice. These data provide evidence that S Typhimurium possesses three transketolases that contribute to pathogenesis.
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Affiliation(s)
- Jeff A Shaw
- Department of Medical Microbiology and Immunology, Creighton University School of Medicine, Omaha, Nebraska 68178
| | - Calvin A Henard
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado 80011
| | - Lin Liu
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado 80011
| | - Lynne M Dieckman
- Department of Chemistry, Creighton University, Omaha, Nebraska 68178
| | - Andrés Vázquez-Torres
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado 80011; Veterans Affairs Eastern Colorado Health Care System, Denver, Colorado 80220
| | - Travis J Bourret
- Department of Medical Microbiology and Immunology, Creighton University School of Medicine, Omaha, Nebraska 68178.
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Bourret TJ, Liu L, Shaw JA, Husain M, Vázquez-Torres A. Magnesium homeostasis protects Salmonella against nitrooxidative stress. Sci Rep 2017; 7:15083. [PMID: 29118452 PMCID: PMC5678156 DOI: 10.1038/s41598-017-15445-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 10/27/2017] [Indexed: 11/09/2022] Open
Abstract
The PhoPQ two-component regulatory system coordinates the response of Salmonella enterica serovar Typhimurium to diverse environmental challenges encountered during infection of hosts, including changes in Mg2+ concentrations, pH, and antimicrobial peptides. Moreover, PhoPQ-dependent regulation of gene expression promotes intracellular survival of Salmonella in macrophages, and contributes to the resistance of this pathogen to reactive nitrogen species (RNS) generated from the nitric oxide produced by the inducible nitric oxide (NO) synthase of macrophages. We report here that Salmonella strains with mutations of phoPQ are hypersensitive to killing by RNS generated in vitro. The increased susceptibility of ∆phoQ Salmonella to RNS requires molecular O2 and coincides with the nitrotyrosine formation, the oxidation of [4Fe-4S] clusters of dehydratases, and DNA damage. Mutations of respiratory NADH dehydrogenases prevent nitrotyrosine formation and abrogate the cytotoxicity of RNS against ∆phoQ Salmonella, presumably by limiting the formation of peroxynitrite (ONOO-) arising from the diffusion-limited reaction of exogenous NO and endogenous superoxide (O2•-) produced in the electron transport chain. The mechanism underlying PhoPQ-mediated resistance to RNS is linked to the coordination of Mg2+ homeostasis through the PhoPQ-regulated MgtA transporter. Collectively, our investigations are consistent with a model in which PhoPQ-dependent Mg2+ homeostasis protects Salmonella against nitrooxidative stress.
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Affiliation(s)
- Travis J Bourret
- Department of Medical Microbiology and Immunology, 2500 California Plaza, Creighton University, Criss I, Rm 521, Omaha, NE 68178, USA.
| | - Lin Liu
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, 80045, USA
| | - Jeff A Shaw
- Department of Medical Microbiology and Immunology, 2500 California Plaza, Creighton University, Criss I, Rm 521, Omaha, NE 68178, USA
| | - Maroof Husain
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, 80045, USA
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Alabama Birmingham, Birmingham, Alabama, 35294, USA
| | - Andrés Vázquez-Torres
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, 80045, USA
- Veterans Affairs Eastern Colorado Health Care System, 1055 Clermont Street, Denver, DO 80220, USA
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Jacques BJ, Bourret TJ, Shaffer JJ. Role of Fly Cleaning Behavior on Carriage of Escherichia coli and Pseudomonas aeruginosa. J Med Entomol 2017; 54:1712-1717. [PMID: 28981669 PMCID: PMC5850793 DOI: 10.1093/jme/tjx124] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Indexed: 06/07/2023]
Abstract
Flies are known to be mechanical vectors of bacterial, viral, and parasitic diseases. Although flies are known to transmit disease, the effects of cleaning behavior have not been well studied. This study quantified the cleaning effectiveness and behavior of three fly species: Sarcophaga bullata, Musca domestica L., and Drosophila virilis. Flies were transferred to plates of Escherichia coli or Pseudomonas aeruginosa and allowed to walk on the bacteria for a total of 5 min. After the flies were contaminated, they were either immediately collected to quantify bacteria or were placed onto sterile plates to clean for 5 or 10 min. After cleaning, flies were placed into tubes with 1 ml of sterile 0.85% saline and were gently shaken for 1 min to remove bacteria. A serial dilution was made and 50-µl spot titers were plated. Cleaning behavior was also monitored and scored for a period of 5 min. Results demonstrate a bacterial reduction for both bacteria on all three fly species. Sarcophaga bullata and D. virilis both showed a significant reduction of both bacteria within 10 min, whereas M. domestica only showed a significant reduction in P. aeruginosa. Cleaning behavior increased significantly in flies that were exposed to bacteria compared to flies that were not exposed to bacteria. This study is important, as it demonstrates that fly cleaning could affect mechanical transmission of disease, and additional studies should look at flies' abilities to remove other types of microorganisms.
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Affiliation(s)
- B J Jacques
- Department of Biology, University of Nebraska at Kearney, 2401 11th Ave., Kearney, NE 68849 (; )
| | - T J Bourret
- Department of Medical Microbiology and Immunology, Creighton University School of Medicine, 2500 California Plaza, Omaha, NE 68178 ()
| | - J J Shaffer
- Department of Biology, University of Nebraska at Kearney, 2401 11th Ave., Kearney, NE 68849 (; )
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Bourret TJ, Lawrence KA, Shaw JA, Lin T, Norris SJ, Gherardini FC. The Nucleotide Excision Repair Pathway Protects Borrelia burgdorferi from Nitrosative Stress in Ixodes scapularis Ticks. Front Microbiol 2016; 7:1397. [PMID: 27656169 PMCID: PMC5013056 DOI: 10.3389/fmicb.2016.01397] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 08/24/2016] [Indexed: 12/28/2022] Open
Abstract
The Lyme disease spirochete Borrelia burgdorferi encounters a wide range of environmental conditions as it cycles between ticks of the genus Ixodes and its various mammalian hosts. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are potent antimicrobial molecules generated during the innate immune response to infection, however, it is unclear whether ROS and RNS pose a significant challenge to B. burgdorferi in vivo. In this study, we screened a library of B. burgdorferi strains with mutations in DNA repair genes for increased susceptibility to ROS or RNS in vitro. Strains with mutations in the methyl-directed mismatch repair gene mutS1 are hypersensitive to killing by ROS, while strains lacking the nucleotide excision repair (NER) gene uvrB show increased susceptibility to both ROS and RNS. Therefore, mutS1-deficient and uvrB-deficient strains were compared for their ability to complete their infectious cycle in Swiss Webster mice and I. scapularis ticks to help identify sites of oxidative and nitrosative stresses encountered by B. burgdorferi in vivo. Both mutS1 and uvrB were dispensable for infection of mice, while uvrB promoted the survival of spirochetes in I. scapularis ticks. The decreased survival of uvrB-deficient B. burgdorferi was associated with the generation of RNS in I. scapularis midguts and salivary glands during feeding. Collectively, these data suggest that B. burgdorferi must withstand cytotoxic levels of RNS produced during infection of I. scapularis ticks.
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Affiliation(s)
- Travis J Bourret
- Department of Medical Microbiology and Immunology, Creighton University Omaha, NE, USA
| | - Kevin A Lawrence
- Gene Regulation Section, Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health Hamilton, MT, USA
| | - Jeff A Shaw
- Department of Medical Microbiology and Immunology, Creighton University Omaha, NE, USA
| | - Tao Lin
- Department of Pathology and Laboratory Medicine, McGovern Medical School, University of Texas Health Science Center at Houston Houston, TX, USA
| | - Steven J Norris
- Department of Pathology and Laboratory Medicine, McGovern Medical School, University of Texas Health Science Center at Houston Houston, TX, USA
| | - Frank C Gherardini
- Gene Regulation Section, Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health Hamilton, MT, USA
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Bourret TJ, Boylan JA, Lawrence KA, Gherardini FC. Nitrosative damage to free and zinc-bound cysteine thiols underlies nitric oxide toxicity in wild-type Borrelia burgdorferi. Mol Microbiol 2011; 81:259-73. [PMID: 21564333 PMCID: PMC3147059 DOI: 10.1111/j.1365-2958.2011.07691.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Borrelia burgdorferi encounters potentially harmful reactive nitrogen species (RNS) throughout its infective cycle. In this study, diethylamine NONOate (DEA/NO) was used to characterize the lethal effects of RNS on B. burgdorferi. RNS produce a variety of DNA lesions in a broad spectrum of microbial pathogens; however, levels of the DNA deamination product, deoxyinosine, and the numbers of apurinic/apyrimidinic (AP) sites were identical in DNA isolated from untreated and DEA/NO-treated B. burgdorferi cells. Strains with mutations in the nucleotide excision repair (NER) pathway genes uvrC or uvrB treated with DEA/NO had significantly higher spontaneous mutation frequencies, increased numbers of AP sites in DNA and reduced survival compared with wild-type controls. Polyunsaturated fatty acids in B. burgdorferi cell membranes, which are susceptible to peroxidation by reactive oxygen species (ROS), were not sensitive to RNS-mediated lipid peroxidation. However, treatment of B. burgdorferi cells with DEA/NO resulted in nitrosative damage to several proteins, including the zinc-dependent glycolytic enzyme fructose-1,6-bisphosphate aldolase (BB0445), the Borrelia oxidative stress regulator (BosR) and neutrophil-activating protein (NapA). Collectively, these data suggested that nitrosative damage to proteins harbouring free or zinc-bound cysteine thiols, rather than DNA or membrane lipids underlies RNS toxicity in wild-type B. burgdorferi.
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Affiliation(s)
- Travis J Bourret
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th Street, Hamilton, MT 59840, USA
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Henard CA, Bourret TJ, Song M, Vázquez-Torres A. Control of redox balance by the stringent response regulatory protein promotes antioxidant defenses of Salmonella. J Biol Chem 2010; 285:36785-93. [PMID: 20851888 DOI: 10.1074/jbc.m110.160960] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We report herein a critical role for the stringent response regulatory DnaK suppressor protein (DksA) in the coordination of antioxidant defenses. DksA helps fine-tune the expression of glutathione biosynthetic genes and discrete steps in the pentose phosphate pathway and tricarboxylic acid cycle that are associated with the generation of reducing power. Control of NAD(P)H/NAD(P)(+) redox balance by DksA fuels downstream antioxidant enzymatic systems in nutritionally starving Salmonella. Conditional expression of the glucose-6-phosphate dehydrogenase-encoding gene zwf, shown here to be under DksA control, increases both the NADPH pool and antioxidant defenses of dksA mutant Salmonella. The DksA-mediated coordination of redox balance boosts the antioxidant defenses of stationary phase bacteria. Not only does DksA increase resistance of Salmonella against hydrogen peroxide (H(2)O(2)), but it also promotes fitness of this intracellular pathogen when exposed to oxyradicals produced by the NADPH phagocyte oxidase in an acute model of infection. Given the role of DksA in the adjustment of gene expression in most bacteria undergoing nutritional deprivation, our findings raise the possibility that the control of central metabolic pathways by this regulatory protein maintains redox homeostasis essential for antioxidant defenses in phylogenetically diverse bacterial species.
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Affiliation(s)
- Calvin A Henard
- Department of Microbiology, Anschutz Medical Center, School of Medicine, University of Colorado, Aurora, Colorado 80045, USA
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Husain M, Bourret TJ, McCollister BD, Jones-Carson J, Laughlin J, Vázquez-Torres A. Nitric oxide evokes an adaptive response to oxidative stress by arresting respiration. J Biol Chem 2008; 283:7682-9. [PMID: 18198179 DOI: 10.1074/jbc.m708845200] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Aerobic metabolism generates biologically challenging reactive oxygen species (ROS) by the endogenous autooxidation of components of the electron transport chain (ETC). Basal levels of oxidative stress can dramatically rise upon activation of the NADPH oxidase-dependent respiratory burst. To minimize ROS toxicity, prokaryotic and eukaryotic organisms express a battery of low-molecular-weight thiol scavengers, a legion of detoxifying catalases, peroxidases, and superoxide dismutases, as well as a variety of repair systems. We present herein blockage of bacterial respiration as a novel strategy that helps the intracellular pathogen Salmonella survive extreme oxidative stress conditions. A Salmonella strain bearing mutations in complex I NADH dehydrogenases is refractory to the early NADPH oxidase-dependent antimicrobial activity of IFNgamma-activated macrophages. The ability of NADH-rich, complex I-deficient Salmonella to survive oxidative stress is associated with resistance to peroxynitrite (ONOO(-)) and hydrogen peroxide (H(2)O(2)). Inhibition of respiration with nitric oxide (NO) also triggered a protective adaptive response against oxidative stress. Expression of the NDH-II dehydrogenase decreases NADH levels, thereby abrogating resistance of NO-adapted Salmonella to H(2)O(2). NADH antagonizes the hydroxyl radical (OH(.)) generated in classical Fenton chemistry or spontaneous decomposition of peroxynitrous acid (ONOOH), while fueling AhpCF alkylhydroperoxidase. Together, these findings identify the accumulation of NADH following the NO-mediated inhibition of Salmonella's ETC as a novel antioxidant strategy. NO-dependent respiratory arrest may help mitochondria and a plethora of organisms cope with oxidative stress engendered in situations as diverse as aerobic respiration, ischemia reperfusion, and inflammation.
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Affiliation(s)
- Maroof Husain
- Department of Microbiology, University of Colorado Health Sciences Center at Fitzsimons, Aurora, Colorado 80045, USA
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McCollister BD, Myers JT, Jones-Carson J, Husain M, Bourret TJ, Vázquez-Torres A. N(2)O(3) enhances the nitrosative potential of IFNgamma-primed macrophages in response to Salmonella. Immunobiology 2007; 212:759-69. [PMID: 18086377 DOI: 10.1016/j.imbio.2007.09.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Accepted: 09/28/2007] [Indexed: 01/09/2023]
Abstract
We show here that the nitric oxide (NO)-detoxifying Hmp flavohemoprotein increases by 3-fold the transcription of the Salmonella pathogenicity island 2 (SPI2) in macrophages expressing a functional inducible NO synthase (iNOS). However, Hmp does not prevent NO-related repression of SPI2 transcription in IFNgamma-primed phagocytes, despite preserving intracellular transcription of sdhA sdhB subunits of Salmonella succinate dehydrogenase within both control and IFNgamma-primed phagocytes. To shed light into the seemingly paradoxical role that Hmp plays in protecting intracellular SPI2 expression in various populations of macrophages, N(2)O(3) was quantified as an indicator of the nitrosative potential of Salmonella-infected phagocytes in different states of activation. Hmp was found to prevent the formation of 300nM N(2)O(3)/h/bacteria in IFNgamma-primed macrophages, accounting for about a 60% reduction of the nitrosative power of activated phagocytes. Utilization of the vacuolar ATPase inhibitor bafilomycin indicates that a fourth of the approximately 200nM N(2)O(3)/h sustained by IFNgamma-primed macrophages is generated in endosomal compartments via condensation of HNO(2). In sharp contrast, control macrophages infected with wild-type Salmonella produce as little N(2)O(3) as iNOS-deficient controls. Collectively, these findings indicate that the NO-metabolizing activity of Salmonella Hmp is functional in both control and IFNgamma-primed macrophages. Nonetheless, a substantial amount of the NO generated by IFNgamma-primed macrophages gives rise to N(2)O(3), a species that not only enhances the nitrosative potential of activated phagocytes but also avoids detoxification by Salmonella Hmp.
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Affiliation(s)
- Bruce D McCollister
- Department of Microbiology, University of Colorado Health Sciences Center, Aurora, CO 80010, USA
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McCollister BD, Bourret TJ, Gill R, Jones-Carson J, Vázquez-Torres A. Repression of SPI2 transcription by nitric oxide-producing, IFNgamma-activated macrophages promotes maturation of Salmonella phagosomes. ACTA ACUST UNITED AC 2005; 202:625-35. [PMID: 16129704 PMCID: PMC2212872 DOI: 10.1084/jem.20050246] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
By remodeling the phagosomal membrane, the type III secretion system encoded within the Salmonella pathogenicity island-2 (SPI2) helps Salmonella thrive within professional phagocytes. We report here that nitric oxide (NO) generated by IFNγ-activated macrophages abrogates the intracellular survival advantage associated with a functional SPI2 type III secretion system. NO congeners inhibit overall expression of SPI2 effectors encoded both inside and outside the SPI2 gene cluster, reflecting a reduced transcript level of the sensor kinase SsrA that governs overall SPI2 transcription. Down-regulation of SPI2 expression in IFNγ-treated macrophages does not seem to be the result of global NO cytotoxicity, because transcription of the housekeeping rpoD sigma factor remains unchanged, whereas the expression of the hmpA-encoded, NO-metabolizing flavohemoprotein is stimulated. Because of the reduced SPI2 expression, Salmonella-containing vacuoles interact more efficiently with compartments of the late endosomal/lysosomal system in NO-producing, IFNγ-treated macrophages. These findings demonstrate that inhibition of intracellular SPI2 transcription by NO promotes the interaction of Salmonella phagosomes with the degradative compartments required for enhanced antimicrobial activity. Transcriptional repression of a type III secretion system that blocks phagolysosome biogenesis represents a novel mechanism by which NO mediates resistance of IFNγ-activated phagocytes to an intracellular pathogen.
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Affiliation(s)
- Bruce D McCollister
- Department of Microbiology, University of Colorado Health Sciences Center, Aurora, 80010, USA
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