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Chauhan S, Singh A, Tyagi JS. A single-nucleotide mutation in the −10 promoter region inactivates thenarK2Xpromoter inMycobacterium bovisandMycobacterium bovisBCG and has an application in diagnosis. FEMS Microbiol Lett 2010; 303:190-6. [DOI: 10.1111/j.1574-6968.2009.01876.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Lone AG, Deslandes V, Nash JHE, Jacques M, MacInnes JI. Modulation of gene expression in Actinobacillus pleuropneumoniae exposed to bronchoalveolar fluid. PLoS One 2009; 4:e6139. [PMID: 19578537 PMCID: PMC2700959 DOI: 10.1371/journal.pone.0006139] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Accepted: 06/08/2009] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Actinobacillus pleuropneumoniae, the causative agent of porcine contagious pleuropneumonia, is an important pathogen of swine throughout the world. It must rapidly overcome the innate pulmonary immune defenses of the pig to cause disease. To better understand this process, the objective of this study was to identify genes that are differentially expressed in a medium that mimics the lung environment early in the infection process. METHODS AND PRINCIPAL FINDINGS Since bronchoalveolar lavage fluid (BALF) contains innate immune and other components found in the lungs, we examined gene expression of a virulent serovar 1 strain of A. pleuropneumoniae after a 30 min exposure to BALF, using DNA microarrays and real-time PCR. The functional classes of genes found to be up-regulated most often in BALF were those encoding proteins involved in energy metabolism, especially anaerobic metabolism, and in cell envelope, DNA, and protein biosynthesis. Transcription of a number of known virulence genes including apxIVA and the gene for SapF, a protein which is involved in resistance to antimicrobial peptides, was also up-regulated in BALF. Seventy-nine percent of the genes that were up-regulated in BALF encoded a known protein product, and of these, 44% had been reported to be either expressed in vivo and/or involved in virulence. CONCLUSIONS The results of this study suggest that in early stages of infection, A. pleuropneumoniae may modulate expression of genes involved in anaerobic energy generation and in the synthesis of proteins involved in cell wall biogenesis, as well as established virulence factors. Given that many of these genes are thought to be expressed in vivo or involved in virulence, incubation in BALF appears, at least partially, to simulate in vivo conditions and may provide a useful medium for the discovery of novel vaccine or therapeutic targets.
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Affiliation(s)
- Abdul G. Lone
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Vincent Deslandes
- Groupe de Recherche sur les Maladies Infectieuses du Porc, Université de Montréal, St-Hyacinthe, Québec, Canada
- Centre de Recherche en Infectiologie Porcine, Université de Montréal, St-Hyacinthe, Québec, Canada
| | - John H. E. Nash
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Mario Jacques
- Groupe de Recherche sur les Maladies Infectieuses du Porc, Université de Montréal, St-Hyacinthe, Québec, Canada
- Centre de Recherche en Infectiologie Porcine, Université de Montréal, St-Hyacinthe, Québec, Canada
| | - Janet I. MacInnes
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
- * E-mail:
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Malm S, Tiffert Y, Micklinghoff J, Schultze S, Joost I, Weber I, Horst S, Ackermann B, Schmidt M, Wohlleben W, Ehlers S, Geffers R, Reuther J, Bange FC. The roles of the nitrate reductase NarGHJI, the nitrite reductase NirBD and the response regulator GlnR in nitrate assimilation of Mycobacterium tuberculosis. MICROBIOLOGY-SGM 2009; 155:1332-1339. [PMID: 19332834 DOI: 10.1099/mic.0.023275-0] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Mycobacterium tuberculosis can utilize various nutrients including nitrate as a source of nitrogen. Assimilation of nitrate requires the reduction of nitrate via nitrite to ammonium, which is then incorporated into metabolic pathways. This study was undertaken to define the molecular mechanism of nitrate assimilation in M. tuberculosis. Homologues to a narGHJI-encoded nitrate reductase and a nirBD-encoded nitrite reductase have been found on the chromosome of M. tuberculosis. Previous studies have implied a role for NarGHJI in nitrate respiration rather than nitrate assimilation. Here, we show that a narG mutant of M. tuberculosis failed to grow on nitrate. A nirB mutant of M. tuberculosis failed to grow on both nitrate and nitrite. Mutant strains of Mycobacterium smegmatis mc(2)155 that are unable to grow on nitrate were isolated. The mutants were rescued by screening a cosmid library from M. tuberculosis, and a gene with homology to the response regulator gene glnR of Streptomyces coelicolor was identified. A DeltaglnR mutant of M. tuberculosis was generated, which also failed to grow on nitrate, but regained its ability to utilize nitrate when nirBD was expressed from a plasmid, suggesting a role of GlnR in regulating nirBD expression. A specific binding site for GlnR within the nirB promoter was identified and confirmed by electrophoretic mobility shift assay using purified recombinant GlnR. Semiquantitative reverse transcription PCR, as well as microarray analysis, demonstrated upregulation of nirBD expression in response to GlnR under nitrogen-limiting conditions. In summary, we conclude that NarGHJI and NirBD of M. tuberculosis mediate the assimilatory reduction of nitrate and nitrite, respectively, and that GlnR acts as a transcriptional activator of nirBD.
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Affiliation(s)
- Sven Malm
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Yvonne Tiffert
- Microbiology/Biotechnology, Microbiological Institute, Faculty of Biology, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Julia Micklinghoff
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Sonja Schultze
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Insa Joost
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Isabel Weber
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Sarah Horst
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Birgit Ackermann
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Mascha Schmidt
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Wolfgang Wohlleben
- Microbiology/Biotechnology, Microbiological Institute, Faculty of Biology, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Stefan Ehlers
- Molecular Infection Biology, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, 23845 Borstel, Germany
| | - Robert Geffers
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Jens Reuther
- Microbiology/Biotechnology, Microbiological Institute, Faculty of Biology, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Franz-Christoph Bange
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
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Kurosu M, Crick DC. MenA is a promising drug target for developing novel lead molecules to combat Mycobacterium tuberculosis. Med Chem 2009; 5:197-207. [PMID: 19275719 DOI: 10.2174/157340609787582882] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Potent inhibitors of MenA (1,4-dihydroxy-2-naphtoate prenyltrasferase) in Mycobacterium tuberculosis are identified, and are also effective in inhibiting growth of Mycobacterium tuberculosis at low concentrations. The MenA inhibitors possess common chemical structural features of (alkylamino)oalkoxyphenyl)(phenyl)methanones. Significantly, the MenA inhibitors can be synthesized in a few steps with high overall yields. The representative MenA inhibitors are highly effective in killing nonreplicating Mycobacterium tuberculosis that is evaluated by using the Wayne low oxygen model. In addition, a series of drug resistant Mycobacterium spp. are sensitive to the MenA inhibitors. The results are expected to be of significance in terms of discovering new lead compounds that can be developed into new drugs to combat unmet diseases caused by Mycobacterium tuberculosis.
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Affiliation(s)
- Michio Kurosu
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1682, USA.
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Sohaskey CD, Modesti L. Differences in nitrate reduction between Mycobacterium tuberculosis and Mycobacterium bovis are due to differential expression of both narGHJI and narK2. FEMS Microbiol Lett 2008; 290:129-34. [DOI: 10.1111/j.1574-6968.2008.01424.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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Identification of a repressor of a truncated denitrification pathway in Moraxella catarrhalis. J Bacteriol 2008; 190:7762-72. [PMID: 18820017 DOI: 10.1128/jb.01032-08] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Growth of Moraxella catarrhalis in a biofilm resulted in marked upregulation of two open reading frames (ORFs), aniA and norB, predicted to encode a nitrite reductase and a nitric oxide reductase, respectively (W. Wang, L. Reitzer, D. A. Rasko, M. M. Pearson, R. J. Blick, C. Laurence, and E. J. Hansen, Infect. Immun. 75:4959-4971, 2007). An ORF designated nsrR, which was located between aniA and norB, was shown to encode a predicted transcriptional regulator. Inactivation of nsrR resulted in increased expression of aniA and norB in three different M. catarrhalis strains, as measured by both DNA microarray analysis and quantitative reverse transcriptase PCR. Provision of a wild-type nsrR gene in trans in an nsrR mutant resulted in decreased expression of the AniA protein. DNA microarray analysis revealed that two other ORFs (MC ORF 683 and MC ORF 1550) were also consistently upregulated in an nsrR mutant. Consumption of both nitrite and nitric oxide occurred more rapidly with cells of an nsrR mutant than with wild-type cells. However, growth of nsrR mutants was completely inhibited by a low level of sodium nitrite. This inhibition of growth by nitrite was significantly reversed by introduction of an aniA mutation into the nsrR mutant and was completely reversed by the presence of a wild-type nsrR gene in trans. NsrR regulation of the expression of aniA was sensitive to nitrite, whereas NsrR regulation of norB was sensitive to nitric oxide.
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Van Rhijn I, Godfroid J, Michel A, Rutten V. Bovine tuberculosis as a model for human tuberculosis: advantages over small animal models. Microbes Infect 2008; 10:711-5. [DOI: 10.1016/j.micinf.2008.04.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 03/31/2008] [Accepted: 04/14/2008] [Indexed: 10/22/2022]
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Mycobacterium bovis BCG vaccine strains lack narK2 and narX induction and exhibit altered phenotypes during dormancy. Infect Immun 2008; 76:2587-93. [PMID: 18362135 DOI: 10.1128/iai.01235-07] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis is the causative agent of tuberculosis, a disease that affects one-third of the world's population. The sole extant vaccine for tuberculosis is the live attenuated Mycobacterium bovis bacillus Calmette-Guerin (BCG). We examined 13 representative BCG strains from around the world to ascertain their ability to express DosR-regulated dormancy antigens. These are known to be recognized by T cells of M. tuberculosis-infected individuals, especially those harboring latent infections. Differences in the expression of these antigens could be valuable for use as diagnostic markers to distinguish BCG vaccination from latent tuberculosis. We determined that all BCG strains were defective for the induction of two dormancy genes: narK2 (Rv1737c) and narX (Rv1736c). NarK2 is known to be necessary for nitrate respiration during anaerobic dormancy. Analysis of the narK2/X promoter region revealed a base substitution mutation in all tested BCG strains and M. bovis in comparison to the M. tuberculosis sequence. We also show that nitrate reduction by BCG strains during dormancy was greatly reduced compared to M. tuberculosis and varied between tested strains. Several dormancy regulon transcriptional differences were also identified among the strains, as well as variation in their growth and survival. These findings demonstrate defects in DosR regulon expression during dormancy and phenotypic variation between commonly used BCG vaccine strains.
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Rollins SM, Peppercorn A, Young JS, Drysdale M, Baresch A, Bikowski MV, Ashford DA, Quinn CP, Handfield M, Hillman JD, Lyons CR, Koehler TM, Calderwood SB, Ryan ET. Application of in vivo induced antigen technology (IVIAT) to Bacillus anthracis. PLoS One 2008; 3:e1824. [PMID: 18350160 PMCID: PMC2265799 DOI: 10.1371/journal.pone.0001824] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Accepted: 02/05/2008] [Indexed: 01/23/2023] Open
Abstract
In vivo induced antigen technology (IVIAT) is an immuno-screening technique that identifies bacterial antigens expressed during infection and not during standard in vitro culturing conditions. We applied IVIAT to Bacillus anthracis and identified PagA, seven members of a N-acetylmuramoyl-L-alanine amidase autolysin family, three P60 family lipoproteins, two transporters, spore cortex lytic protein SleB, a penicillin binding protein, a putative prophage holin, respiratory nitrate reductase NarG, and three proteins of unknown function. Using quantitative real-time PCR comparing RNA isolated from in vitro cultured B. anthracis to RNA isolated from BALB/c mice infected with virulent Ames strain B. anthracis, we confirmed induced expression in vivo for a subset of B. anthracis genes identified by IVIAT, including L-alanine amidases BA3767, BA4073, and amiA (pXO2-42); the bacteriophage holin gene BA4074; and pagA (pXO1-110). The exogenous addition of two purified putative autolysins identified by IVIAT, N-acetylmuramoyl-L-alanine amidases BA0485 and BA2446, to vegetative B. anthracis cell suspensions induced a species-specific change in bacterial morphology and reduction in viable bacterial cells. Many of the proteins identified in our screen are predicted to affect peptidoglycan re-modeling, and our results support significant cell wall structural remodeling activity during B. anthracis infection. Identification of L-alanine amidases with B. anthracis specificity may suggest new potential therapeutic targets.
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Affiliation(s)
- Sean M Rollins
- Massachusetts General Hospital, Boston, Massachusetts, United States of America.
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Khan A, Sarkar D. A simple whole cell based high throughput screening protocol using Mycobacterium bovis BCG for inhibitors against dormant and active tubercle bacilli. J Microbiol Methods 2008; 73:62-8. [PMID: 18328582 DOI: 10.1016/j.mimet.2008.01.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 01/30/2008] [Accepted: 01/31/2008] [Indexed: 10/22/2022]
Abstract
This study aimed at developing a whole cell based high throughput screening protocol to identify inhibitors against both active and dormant tubercle bacilli. A respiratory type of nitrate reductase (NarGHJI), which was induced during dormancy, could reflect the viability of dormant bacilli of Mycobacterium bovis BCG in microplate adopted model of in vitro dormancy. Correlation between reduction in viability and nitrate reductase activity was seen clearly when dormant stage inhibitor metronidazole and itaconic anhydride were applied in this in vitro microplate model. Active replicating stage could also be monitored in the same assay by measuring the A(620) of the culture. MIC values of 0.08, 0.075, 0.3 and 3.0 microg/ml, determined through monitoring A(620) in this assay for rifampin, isoniazid, streptomycin and ethambutol respectively, were well in agreement with previously reported by BACTEC and Bio-Siv assays. S/N ratio and Z' factor for the assay were 8.5 and 0.81 respectively which indicated the robustness of the protocol. Altogether the assay provides an easy, inexpensive, rapid, robust and high content screening tool to search novel antitubercular molecules against both active and dormant bacilli.
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Affiliation(s)
- Arshad Khan
- CombiChem Bio Resource Center, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India
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Srivastava V, Jain A, Srivastava BS, Srivastava R. Selection of genes of Mycobacterium tuberculosis upregulated during residence in lungs of infected mice. Tuberculosis (Edinb) 2007; 88:171-7. [PMID: 18054522 DOI: 10.1016/j.tube.2007.10.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 08/26/2007] [Accepted: 10/23/2007] [Indexed: 11/30/2022]
Abstract
In sequel to previous report [Srivastava V, Rouanet C, Srivastava R, Ramalingam B, Locht C, Srivastava BS. Macrophage-specific Mycobacterium tuberculosis genes: identification by green fluorescent protein and kanamycin resistance selection. Microbiology 2007;153:659-66], the genes of Mycobacterium tuberculosis upregulated during residence in lungs of infected mice were identified in an in vivo expression system based on kanamycin resistance. A promoter library of M. tuberculosis was constructed in a promoter trap shuttle vector pLL192 containing an artificial bicistronic operon composed of promoterless green fluorescent protein gene followed by kanamycin resistance gene. The library was introduced in M. bovis BCG and then infected in mice by intravenous route. Mice were treated twice daily with 40 mg/kg dose of kanamycin by intramuscular route for 21 days. Recombinant BCG recovered from the lungs were reinfected in mice to enrich clones surviving kanamycin treatment in the lung but sensitive to killing by kanamycin in vitro. After nucleotide sequencing of inserts from these clones, 20 genes belonging to fatty acids metabolism, membrane transport, nitric oxide defence and PE_PGRS/PPE family were identified. Real-time PCR analysis using RNA isolated from M. tuberculosis grown in vitro and from the lungs, confirmed upregulation of genes from 2 to 20-fold in vivo compared to growth in vitro. Several of these select 20 genes were also found upregulated ex vivo in macrophage-like cell line J774A.1, thus, suggesting a correlation in mycobacterial gene expression between ex vivo and in vivo conditions.
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Affiliation(s)
- Vikas Srivastava
- Microbiology Division, Central Drug Research Institute, Lucknow 226001, India.
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Ventura M, Canchaya C, Tauch A, Chandra G, Fitzgerald GF, Chater KF, van Sinderen D. Genomics of Actinobacteria: tracing the evolutionary history of an ancient phylum. Microbiol Mol Biol Rev 2007; 71:495-548. [PMID: 17804669 PMCID: PMC2168647 DOI: 10.1128/mmbr.00005-07] [Citation(s) in RCA: 597] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Actinobacteria constitute one of the largest phyla among bacteria and represent gram-positive bacteria with a high G+C content in their DNA. This bacterial group includes microorganisms exhibiting a wide spectrum of morphologies, from coccoid to fragmenting hyphal forms, as well as possessing highly variable physiological and metabolic properties. Furthermore, Actinobacteria members have adopted different lifestyles, and can be pathogens (e.g., Corynebacterium, Mycobacterium, Nocardia, Tropheryma, and Propionibacterium), soil inhabitants (Streptomyces), plant commensals (Leifsonia), or gastrointestinal commensals (Bifidobacterium). The divergence of Actinobacteria from other bacteria is ancient, making it impossible to identify the phylogenetically closest bacterial group to Actinobacteria. Genome sequence analysis has revolutionized every aspect of bacterial biology by enhancing the understanding of the genetics, physiology, and evolutionary development of bacteria. Various actinobacterial genomes have been sequenced, revealing a wide genomic heterogeneity probably as a reflection of their biodiversity. This review provides an account of the recent explosion of actinobacterial genomics data and an attempt to place this in a biological and evolutionary context.
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Affiliation(s)
- Marco Ventura
- Department of Genetics, Biology of Microorganisms, Anthropology and Evolution, University of Parma, parco Area delle Scienze 11a, 43100 Parma, Italy.
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Khan A, Akhtar S, Ahmad JN, Sarkar D. Presence of a functional nitrate assimilation pathway in Mycobacterium smegmatis. Microb Pathog 2007; 44:71-7. [PMID: 17888619 DOI: 10.1016/j.micpath.2007.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2007] [Indexed: 11/26/2022]
Abstract
Ability of Mycobacterium smegmatis to assimilate nitrate was evaluated in its active and dormant phase. Nitrate (10 mM), nitrite (0.5 mM) and ammonia (10mM) allowed growth of M. smegmatis concomitant with their complete depletion from the culture in 144, 120 and 96 h, respectively, when used as sole nitrogen source. Azide (50 microM) stopped the growth of M. smegmatis when nitrate was used as sole nitrogen source. l-methionine-S-sulfoximine (l-MSO), which is a well-known inhibitor of glutamine synthetase, an enzyme also involved in nitrogen metabolic pathway, when applied at 10 microg/ml concentration, completely inhibited the growth of the organism when nitrate or nitrite was used as sole nitrogen source. There was no effect of either azide or l-MSO at above concentrations on the growth of the organism when asparagine or ammonia was used as sole nitrogen source. More significantly, utilization of nitrate, nitrite and ammonia continued even in oxygen depletion induced dormant culture at the rates of 289, 25 and 354 microM/day, respectively. These rates were 5-8 times slower than the rates of 1966, 127 and 2890 microM/day, respectively, in active replicating phase. In the presence of azide (50 microM) and l-MSO (10 microg/ml), 2.1 and 1.51 logs reduction in viability of dormant M. smegmatis was observed using nitrate and nitrite, respectively, as sole nitrogen source. Altogether, the results indicated the presence of nitrate assimilation pathway operating in both active and dormant stage of M. smegmatis.
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Affiliation(s)
- Arshad Khan
- Combichem Bio Resource Center, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.
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Murphy DJ, Brown JR. Identification of gene targets against dormant phase Mycobacterium tuberculosis infections. BMC Infect Dis 2007; 7:84. [PMID: 17655757 PMCID: PMC1950094 DOI: 10.1186/1471-2334-7-84] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 07/26/2007] [Indexed: 12/30/2022] Open
Abstract
Background Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), infects approximately 2 billion people worldwide and is the leading cause of mortality due to infectious disease. Current TB therapy involves a regimen of four antibiotics taken over a six month period. Patient compliance, cost of drugs and increasing incidence of drug resistant M. tuberculosis strains have added urgency to the development of novel TB therapies. Eradication of TB is affected by the ability of the bacterium to survive up to decades in a dormant state primarily in hypoxic granulomas in the lung and to cause recurrent infections. Methods The availability of M. tuberculosis genome-wide DNA microarrays has lead to the publication of several gene expression studies under simulated dormancy conditions. However, no single model best replicates the conditions of human pathogenicity. In order to identify novel TB drug targets, we performed a meta-analysis of multiple published datasets from gene expression DNA microarray experiments that modeled infection leading to and including the dormant state, along with data from genome-wide insertional mutagenesis that examined gene essentiality. Results Based on the analysis of these data sets following normalization, several genome wide trends were identified and used to guide the selection of targets for therapeutic development. The trends included the significant up-regulation of genes controlled by devR, down-regulation of protein and ATP synthesis, and the adaptation of two-carbon metabolism to the hypoxic and nutrient limited environment of the granuloma. Promising targets for drug discovery were several regulatory elements (devR/devS, relA, mprAB), enzymes involved in redox balance and respiration, sulfur transport and fixation, pantothenate, isoprene, and NAD biosynthesis. The advantages and liabilities of each target are discussed in the context of enzymology, bacterial pathways, target tractability, and drug development. Conclusion Based on our bioinformatics analysis and additional discussion of in-depth biological rationale, several novel anti-TB targets have been proposed as potential opportunities to improve present therapeutic treatments for this disease.
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Affiliation(s)
- Dennis J Murphy
- Informatics, Molecular Discovery Research, GlaxoSmithKline, 1250 South Collegeville Road, UP1345, PO Box 5089, Collegeville, PA 19426-0989, USA
- Department of Biochemistry, UW2523, Cardiovascular and Urogenital CEDD, GlaxoSmithKline, 709 Swedeland Road, Box 1539, King of Prussia, PA 19406, USA
| | - James R Brown
- Informatics, Molecular Discovery Research, GlaxoSmithKline, 1250 South Collegeville Road, UP1345, PO Box 5089, Collegeville, PA 19426-0989, USA
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Palmer KL, Brown SA, Whiteley M. Membrane-bound nitrate reductase is required for anaerobic growth in cystic fibrosis sputum. J Bacteriol 2007; 189:4449-55. [PMID: 17400735 PMCID: PMC1913347 DOI: 10.1128/jb.00162-07] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Accepted: 03/22/2007] [Indexed: 11/20/2022] Open
Abstract
The autosomal recessive disorder cystic fibrosis (CF) affects approximately 70,000 people worldwide and is characterized by chronic bacterial lung infections with the opportunistic pathogen Pseudomonas aeruginosa. To form a chronic CF lung infection, P. aeruginosa must grow and proliferate within the CF lung, and the highly viscous sputum within the CF lung provides a likely growth substrate. Recent evidence indicates that anaerobic microenvironments may be present in the CF lung sputum layer. Since anaerobic growth significantly enhances P. aeruginosa biofilm formation and antibiotic resistance, it is important to examine P. aeruginosa physiology and metabolism in anaerobic environments. Measurement of nitrate levels revealed that CF sputum contains sufficient nitrate to support significant P. aeruginosa growth anaerobically, and mutational analysis revealed that the membrane-bound nitrate reductase is essential for P. aeruginosa anaerobic growth in an in vitro CF sputum medium. In addition, expression of genes coding for the membrane-bound nitrate reductase complex is responsive to CF sputum nitrate levels. These findings suggest that the membrane-bound nitrate reductase is critical for P. aeruginosa anaerobic growth with nitrate in the CF lung.
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Affiliation(s)
- Kelli L Palmer
- Section of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, TX 78712, USA
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Van Alst NE, Picardo KF, Iglewski BH, Haidaris CG. Nitrate sensing and metabolism modulate motility, biofilm formation, and virulence in Pseudomonas aeruginosa. Infect Immun 2007; 75:3780-90. [PMID: 17526746 PMCID: PMC1952006 DOI: 10.1128/iai.00201-07] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infection by the bacterial opportunist Pseudomonas aeruginosa frequently assumes the form of a biofilm, requiring motility for biofilm formation and dispersal and an ability to grow in nutrient- and oxygen-limited environments. Anaerobic growth by P. aeruginosa is accomplished through the denitrification enzyme pathway that catalyzes the sequential reduction of nitrate to nitrogen gas. Mutants mutated in the two-component nitrate sensor-response regulator and in membrane nitrate reductase displayed altered motility and biofilm formation compared to wild-type P. aeruginosa PAO1. Analysis of additional nitrate dissimilation mutants demonstrated a second level of regulation in P. aeruginosa motility that is independent of nitrate sensor-response regulator function and is associated with nitric oxide production. Because motility and biofilm formation are important for P. aeruginosa pathogenicity, we examined the virulence of selected regulatory and structural gene mutants in the surrogate model host Caenorhabditis elegans. Interestingly, the membrane nitrate reductase mutant was avirulent in C. elegans, while nitrate sensor-response regulator mutants were fully virulent. The data demonstrate that nitrate sensing, response regulation, and metabolism are linked directly to factors important in P. aeruginosa pathogenesis.
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Affiliation(s)
- Nadine E Van Alst
- Department of Microbiology and Immunology, Box 672, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA
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67
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Papadopoulou MV, Bloomer WD, McNeil MR. NLCQ-1 and NLCQ-2, two new agents with activity against dormant Mycobacterium tuberculosis. Int J Antimicrob Agents 2007; 29:724-7. [PMID: 17379483 DOI: 10.1016/j.ijantimicag.2007.01.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 01/23/2007] [Accepted: 01/24/2007] [Indexed: 10/23/2022]
Abstract
4-[3-(2-Nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1; NSC 709257) and 4-[4-(2-nitro-1-imidazolyl)-butylamino]-7-chloroquinoline hydrochloride (NLCQ-2), two weak DNA-intercalating nitroimidazole-based bioreductive prodrugs, have been tested against dormant Mycobacterium tuberculosis and demonstrated a significant activity comparable with that of the nitroimidazopyran PA-824. Minimum bactericidal concentrations (MBCs) of 3.1-18.4 and 4.9-9.8 microg/mL were obtained for NLCQ-1 and NLCQ-2, respectively. In the same test setting; the corresponding MBC range for PA-824 was 6.4-12.8 microg/mL. For rifampicin, isoniazid, minocycline, streptomycin, clarithromycin and capreomycin, the corresponding MBC values were 2.5, >100, >156.25, >12.5, >312.5 and 37.5 microg/mL, respectively. Toxicity against Vero cells provided 50% inhibitory concentrations (IC(50)) of 146.7, >640 and >640 microg/mL for NLCQ-1, NLCQ-2 and PA-824, respectively. Therefore, the selectivity index (SI) was 8-47.3, >65.3-130.6 and >50-100 for NLCQ-1, NLCQ-2 and PA-824, respectively. These results suggest the potential usefulness of these compounds in the therapy of the latent form of tuberculosis.
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Affiliation(s)
- Maria V Papadopoulou
- Department of Radiation Medicine, Evanston Northwestern Healthcare, Evanston, 2650 Ridge Ave., IL 60201, USA.
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68
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Nishimura T, Vertès AA, Shinoda Y, Inui M, Yukawa H. Anaerobic growth of Corynebacterium glutamicum using nitrate as a terminal electron acceptor. Appl Microbiol Biotechnol 2007; 75:889-97. [PMID: 17347820 DOI: 10.1007/s00253-007-0879-y] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 01/30/2007] [Accepted: 02/01/2007] [Indexed: 10/23/2022]
Abstract
Corynebacterium glutamicum, a gram-positive soil bacterium, has been regarded as an aerobe because its growth by fermentative catabolism or by anaerobic respiration has, to this date, not been demonstrated. In this study, we report on the anaerobic growth of C. glutamicum in the presence of nitrate as a terminal electron acceptor. C. glutamicum strains R and ATCC13032 consumed nitrate and excreted nitrite during growth under anaerobic, but not aerobic, conditions. This was attributed to the presence of a narKGHJI gene cluster with high similarity to the Escherichia coli narK gene and narGHJI operon. The gene encodes a nitrate/nitrite transporter, whereas the operon encodes a respiratory nitrate reductase. Transposonal inactivation of C. glutamicum narG or narH resulted in mutants with impaired anaerobic growth on nitrate because of their inability to convert nitrate to nitrite. Further analysis revealed that in C. glutamicum, narK and narGHJI are cotranscribed as a single narKGHJI operon, the expression of which is activated under anaerobic conditions in the presence of nitrate. C. glutamicum is therefore a facultative anaerobe.
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Affiliation(s)
- Taku Nishimura
- Microbiology Research Group, Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizu-cho, Soraku-gun, Kyoto 619-0292, Japan
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69
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Beste DJV, Hooper T, Stewart G, Bonde B, Avignone-Rossa C, Bushell ME, Wheeler P, Klamt S, Kierzek AM, McFadden J. GSMN-TB: a web-based genome-scale network model of Mycobacterium tuberculosis metabolism. Genome Biol 2007; 8:R89. [PMID: 17521419 PMCID: PMC1929162 DOI: 10.1186/gb-2007-8-5-r89] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 04/16/2007] [Accepted: 05/23/2007] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND An impediment to the rational development of novel drugs against tuberculosis (TB) is a general paucity of knowledge concerning the metabolism of Mycobacterium tuberculosis, particularly during infection. Constraint-based modeling provides a novel approach to investigating microbial metabolism but has not yet been applied to genome-scale modeling of M. tuberculosis. RESULTS GSMN-TB, a genome-scale metabolic model of M. tuberculosis, was constructed, consisting of 849 unique reactions and 739 metabolites, and involving 726 genes. The model was calibrated by growing Mycobacterium bovis bacille Calmette Guérin in continuous culture and steady-state growth parameters were measured. Flux balance analysis was used to calculate substrate consumption rates, which were shown to correspond closely to experimentally determined values. Predictions of gene essentiality were also made by flux balance analysis simulation and were compared with global mutagenesis data for M. tuberculosis grown in vitro. A prediction accuracy of 78% was achieved. Known drug targets were predicted to be essential by the model. The model demonstrated a potential role for the enzyme isocitrate lyase during the slow growth of mycobacteria, and this hypothesis was experimentally verified. An interactive web-based version of the model is available. CONCLUSION The GSMN-TB model successfully simulated many of the growth properties of M. tuberculosis. The model provides a means to examine the metabolic flexibility of bacteria and predict the phenotype of mutants, and it highlights previously unexplored features of M. tuberculosis metabolism.
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Affiliation(s)
- Dany JV Beste
- School of Biomedical and Molecular Sciences, University of Surrey, Stag Hill, Guildford, Surrey, GU2 7XH, UK
| | - Tracy Hooper
- School of Biomedical and Molecular Sciences, University of Surrey, Stag Hill, Guildford, Surrey, GU2 7XH, UK
| | - Graham Stewart
- School of Biomedical and Molecular Sciences, University of Surrey, Stag Hill, Guildford, Surrey, GU2 7XH, UK
| | - Bhushan Bonde
- School of Biomedical and Molecular Sciences, University of Surrey, Stag Hill, Guildford, Surrey, GU2 7XH, UK
| | - Claudio Avignone-Rossa
- School of Biomedical and Molecular Sciences, University of Surrey, Stag Hill, Guildford, Surrey, GU2 7XH, UK
| | - Michael E Bushell
- School of Biomedical and Molecular Sciences, University of Surrey, Stag Hill, Guildford, Surrey, GU2 7XH, UK
| | - Paul Wheeler
- Tuberculosis Research Group, Veterinary Laboratories Agency (Weybridge), New Haw, Addlestone KT15 3NB, UK
| | - Steffen Klamt
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse, D-39106 Magdeburg, Germany
| | - Andrzej M Kierzek
- School of Biomedical and Molecular Sciences, University of Surrey, Stag Hill, Guildford, Surrey, GU2 7XH, UK
| | - Johnjoe McFadden
- School of Biomedical and Molecular Sciences, University of Surrey, Stag Hill, Guildford, Surrey, GU2 7XH, UK
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70
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Pittman MS, Elvers KT, Lee L, Jones MA, Poole RK, Park SF, Kelly DJ. Growth ofCampylobacter jejunion nitrate and nitrite: electron transport to NapA and NrfA via NrfH and distinct roles for NrfA and the globin Cgb in protection against nitrosative stress. Mol Microbiol 2006; 63:575-90. [PMID: 17241202 DOI: 10.1111/j.1365-2958.2006.05532.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pathways of electron transport to periplasmic nitrate (NapA) and nitrite (NrfA) reductases have been investigated in Campylobacter jejuni, a microaerophilic food-borne pathogen. The nap operon is unusual in lacking napC (encoding a tetra-haem c-type cytochrome) and napF, but contains a novel gene of unknown function, napL. The iron-sulphur protein NapG has a major role in electron transfer to the NapAB complex, but we show that slow nitrate-dependent growth of a napG mutant can be sustained by electron transfer from NrfH, the electron donor to the nitrite reductase NrfA. A napL mutant possessed approximately 50% lower NapA activity than the wild type but showed normal growth with nitrate as the electron acceptor. NrfA was constitutive and was shown to play a role in protection against nitrosative stress in addition to the previously identified NO-inducible single domain globin, Cgb. However, nitrite also induced cgb expression in an NssR-dependent manner, suggesting that growth of C. jejuni with nitrite causes nitrosative stress. This was confirmed by lack of growth of cgb and nssR mutants, and slow growth of the nrfA mutant, in media containing nitrite. Thus, NrfA and Cgb together provide C. jejuni with constitutive and inducible components of a robust defence against nitrosative stress.
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Affiliation(s)
- Marc S Pittman
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
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71
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Sambandamurthy VK, Derrick SC, Hsu T, Chen B, Larsen MH, Jalapathy KV, Chen M, Kim J, Porcelli SA, Chan J, Morris SL, Jacobs WR. Mycobacterium tuberculosis ΔRD1 ΔpanCD: A safe and limited replicating mutant strain that protects immunocompetent and immunocompromised mice against experimental tuberculosis. Vaccine 2006; 24:6309-20. [PMID: 16860907 DOI: 10.1016/j.vaccine.2006.05.097] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Revised: 05/12/2006] [Accepted: 05/22/2006] [Indexed: 11/28/2022]
Abstract
The global epidemic of tuberculosis (TB), fueled by the growing HIV pandemic, warrants the development of a safe and effective vaccine against TB. We report the construction and characterization of an unlinked double deletion mutant of Mycobacterium tuberculosis H37Rv that deletes both the primary attenuating mutation of BCG (DeltaRD1) and two genes required for the synthesis of pantothenate (DeltapanCD). The M. tuberculosis DeltaRD1 DeltapanCD (mc(2)6030) mutant undergoes limited replication in mice, and yet is both significantly safer than BCG in immunocompromised mice and also safe in guinea pigs. Additionally, the mc(2)6030 strain does not reactivate in a mouse chemo-immunosuppression model. Importantly, long-lived protective immune responses following immunization with the mc(2)6030 strain prolong the survival of wild type mice, and CD4-deficient mice against an aerosol challenge with virulent M. tuberculosis. Given its overall safety and effectiveness, the mc(2)6030 live attenuated strain should be considered as a human vaccine candidate for protecting both healthy and HIV-infected individuals against TB.
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Affiliation(s)
- Vasan K Sambandamurthy
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, United States
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72
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Khan A, Sarkar D. Identification of a respiratory-type nitrate reductase and its role for survival of Mycobacterium smegmatis in Wayne model. Microb Pathog 2006; 41:90-5. [PMID: 16806798 DOI: 10.1016/j.micpath.2006.04.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Revised: 04/11/2006] [Accepted: 04/28/2006] [Indexed: 10/24/2022]
Abstract
Nitrate reductase (NR) is found to be expressed in certain mycobacterium sp. whose link with the development of persistence is yet to be resolved. The present study demonstrates the action of selective inhibitors on NR as well as in the survival of Mycobacterium smegmatis using Wayne's model. During gradual shift down to anaerobic stage in Wayne's model, conversion of nitrate to nitrite became apparent in M. smegmatis. More than 97 percent inhibition was observed for the conversion of nitrate to nitrite by azide (0.05 mM) and thiocyanate (20 mM) in both whole-cell as well as its cell-free lysate, respectively. Under identical condition, chlorate (20 mM) inhibited nitrate reduction by 67 and 10 percent, respectively. At these concentrations, neither of azide, thiocyanate nor chlorate had any significant effect on cell growth under aerobic condition. In Wayne's culture model, thiocyanate and chlorate inhibited the growth of M. smegmatis by almost 2 logs at the same concentrations whereas azide inhibited by almost 1.75 log when added at the time of inoculation. Exposure of same culture at 96 h after inoculation in Wayne's model to these inhibitors showed 1.74, 1.95 and 2.37 log inhibition of viable cells with respect to azide, thiocyanate and chlorate. These findings further indicated that NR inhibitors kill the bacilli at anaerobic stage under the experimental condition mentioned. Metronidazole (MTZ) (2 mM) and Nitrofurantoin (NIT) (0.3 mM) reduced the cell number at both stages by <0.7 log. They did not have any effect on NR. Altogether, the results clearly indicate that NR-specific inhibitors could become more promising in killing the bacilli at anaerobic stage than the available conventional drugs.
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Affiliation(s)
- Arshad Khan
- CombiChem Bio Resource Center, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
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73
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Huard RC, Fabre M, de Haas P, Lazzarini LCO, van Soolingen D, Cousins D, Ho JL. Novel genetic polymorphisms that further delineate the phylogeny of the Mycobacterium tuberculosis complex. J Bacteriol 2006; 188:4271-87. [PMID: 16740934 PMCID: PMC1482959 DOI: 10.1128/jb.01783-05] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In a previous report, we described a PCR protocol for the differentiation of the various species of the Mycobacterium tuberculosis complex (MTC) on the basis of genomic deletions (R. C. Huard, L. C. de Oliveira Lazzarini, W. R. Butler, D. van Soolingen, and J. L. Ho, J. Clin. Microbiol. 41:1637-1650, 2003). That report also provided a broad cross-comparison of several previously identified, phylogenetically relevant, long-sequence and single-nucleotide polymorphisms (LSPs and SNPs, respectively). In the present companion report, we expand upon the previous work (i) by continuing the evaluation of known MTC phylogenetic markers in a larger collection of tubercle bacilli (n = 125), (ii) by evaluating additional recently reported MTC species-specific and interspecific polymorphisms, and (iii) by describing the identification and distribution of a number of novel LSPs and SNPs. Notably, new genomic deletions were found in various Mycobacterium tuberculosis strains, new species-specific SNPs were identified for "Mycobacterium canettii," Mycobacterium microti, and Mycobacterium pinnipedii, and, for the first time, intraspecific single-nucleotide DNA differences were discovered for the dassie bacillus, the oryx bacillus, and the two Mycobacterium africanum subtype I variants. Surprisingly, coincident polymorphisms linked one M. africanum subtype I genotype with the dassie bacillus and M. microti with M. pinnipedii, thereby suggesting closer evolutionary ties within each pair of species than had been previously thought. Overall, the presented data add to the genetic definitions of several MTC organisms as well as fine-tune current models for the evolutionary history of the MTC.
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Affiliation(s)
- Richard C Huard
- Division of International Medicine and Infectious Diseases, Department of Medicine, Joan and Sanford I. Weill Medical College, Cornell University, Room A-421, 525 East 68th St., New York, NY 10021, USA
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74
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Filiatrault MJ, Picardo KF, Ngai H, Passador L, Iglewski BH. Identification of Pseudomonas aeruginosa genes involved in virulence and anaerobic growth. Infect Immun 2006; 74:4237-45. [PMID: 16790798 PMCID: PMC1489737 DOI: 10.1128/iai.02014-05] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Revised: 01/31/2006] [Accepted: 04/17/2006] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is a gram-negative, opportunistic pathogen and a significant cause of acute and chronic infections in patients with compromised host defenses. Evidence suggests that within infections P. aeruginosa encounters oxygen limitation and exists in microbial aggregates known as biofilms. However, there is little information that describes genes involved in anaerobic growth of P. aeruginosa and their association with virulence of this pathogen. To identify genes required for anaerobic growth, random transposon (Tn) mutagenesis was used to screen for mutants that demonstrated the inability to grow anaerobically using nitrate as a terminal electron acceptor. Of approximately 35,000 mutants screened, 57 mutants were found to exhibit no growth anaerobically using nitrate. Identification of the genes disrupted by the Tn revealed 24 distinct loci required for anaerobic growth on nitrate, including several genes not previously associated with anaerobic growth of P. aeruginosa. Several of these mutants were capable of growing anaerobically using nitrite and/or arginine, while five mutants were unable to grow anaerobically under any of the conditions tested. Three mutants were markedly attenuated in virulence in the lettuce model of P. aeruginosa infection. These studies have identified novel genes important for anaerobic growth and demonstrate that anaerobic metabolism influences virulence of P. aeruginosa.
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Affiliation(s)
- Melanie J Filiatrault
- University of Rochester School of Medicine and Dentistry, Department of Microbiology and Immunology, 601 Elmwood Avenue, Box 672, Rochester, NY 14642, USA
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Johannesson H, Kasuga T, Schaller RA, Good B, Gardner MJ, Townsend JP, Cole GT, Taylor JW. Phase-specific gene expression underlying morphological adaptations of the dimorphic human pathogenic fungus, Coccidioides posadasii. Fungal Genet Biol 2006; 43:545-59. [PMID: 16697669 DOI: 10.1016/j.fgb.2006.02.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Revised: 02/01/2006] [Accepted: 02/02/2006] [Indexed: 11/17/2022]
Abstract
Coccidioides posadasii is a dimorphic fungal pathogen that grows as a filamentous saprobe in the soil and as endosporulating spherules within the host. To identify genes specific to the pathogenic phase of Co. posadasii, we carried out a large-scale study of gene expression in two isolates of the species. From the sequenced Co. posadasii genome, we chose 1,000 open reading frames to construct a 70-mer microarray. RNA was recovered from both isolates at three life-cycle phases: hyphae, presegmented spherules, and spherules releasing endospores. Comparative hybridizations were conducted in a circuit design, permitting comparison between both isolates at all three life-cycle phases, and among all life-cycle phases for each isolate. By using this approach, we identified 92 genes that were differentially expressed between pathogenic and saprobic phases in both fungal isolates, and 43 genes with consistent differential expression between the two parasitic developmental phases. Genes with elevated expression in the pathogenic phases of both isolates included a number of genes that were involved in the response to environmental stress as well as in the metabolism of lipids. The latter observation is in agreement with previous studies demonstrating that spherules contain a higher proportion of lipids than saprobic phase tissue. Intriguingly, we discovered statistically significant and divergent levels of gene expression between the two isolates profiled for 64 genes. The results suggest that incorporating more than one isolate in the experimental design offers a means of categorizing the large collection of candidate genes that transcriptional profiling typically identifies into those that are strain-specific and those that characterize the entire species.
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Affiliation(s)
- H Johannesson
- Department of Evolution, Genomics and Systematics, Uppsala University, SE-752 36 Uppsala, Sweden
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76
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Haine V, Dozot M, Dornand J, Letesson JJ, De Bolle X. NnrA is required for full virulence and regulates several Brucella melitensis denitrification genes. J Bacteriol 2006; 188:1615-9. [PMID: 16452445 PMCID: PMC1367225 DOI: 10.1128/jb.188.4.1615-1619.2006] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We identified two regulators of denitrification genes in Brucella melitensis 16M: NarR, which regulates the nitrate reductase (nar) operon, and NnrA, which is involved in the expression of the last three reductases of the denitrification pathway (nirK, norB, and nosZ). NnrA is required for virulence in mice and for intracellular resistance to nitric oxide.
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Affiliation(s)
- Valérie Haine
- Unité de Recherche en Biologie Moléculaire (URBM), University of Namur (FUNDP), 61 rue de Bruxelles, B-5000 Namur, Belgium
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77
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Sohaskey CD. Regulation of nitrate reductase activity in Mycobacterium tuberculosis by oxygen and nitric oxide. MICROBIOLOGY-SGM 2005; 151:3803-3810. [PMID: 16272401 DOI: 10.1099/mic.0.28263-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Nitrate reduction by Mycobacterium tuberculosis is regulated by control of the transport of nitrate into the cell by NarK2. When oxygen was introduced into hypoxic cultures, nitrite production was quickly inhibited. The nitrate-reducing enzyme itself is relatively insensitive to oxygen, suggesting that the inhibition of nitrite production by oxygen was a result of interference with nitrate transport. This was not due to degradation of NarK2, as the inhibition was reversed by the removal of oxygen although chloramphenicol prevented new synthesis of NarK2. The oxidant potassium ferricyanide was added to anaerobic cultures to produce a positive redox potential in the absence of oxygen. Nitrite production decreased, signifying that oxidizing conditions, rather than oxygen itself, were responsible for the inhibition of nitrate transport. Nitric oxide added to cultures allowed NarK2 to be active even in the presence of oxygen. A similar result was obtained with hydroxylamine and ethanol, both of which interfere with oxygen utilization and the electron transport chain. It is proposed that NarK2 senses the redox state of the cell, possibly by monitoring the flow of electrons to cytochrome oxidase, and adjusts its activity so that nitrate is transported under reducing, but not under oxidizing, conditions.
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Affiliation(s)
- Charles D Sohaskey
- Department of Veterans Affairs Medical Center, Long Beach, CA 90822, and Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92717, USA
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Davidow A, Kanaujia GV, Shi L, Kaviar J, Guo X, Sung N, Kaplan G, Menzies D, Gennaro ML. Antibody profiles characteristic of Mycobacterium tuberculosis infection state. Infect Immun 2005; 73:6846-51. [PMID: 16177363 PMCID: PMC1230945 DOI: 10.1128/iai.73.10.6846-6851.2005] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The relationship between specific antibody profiles and tuberculosis (TB) state was investigated by measuring serum antibody levels to six Mycobacterium tuberculosis antigens in human subjects grouped into four diagnostic categories: active disease, inactive (past) tuberculosis, latent infection without radiographic chest abnormalities, and infection free. Statistical data analyses showed that the latter two groups were serologically indistinguishable and that active tuberculosis and inactive tuberculosis were characterized by different antibody profiles. Antibodies to the 38-kDa antigen, alanine dehydrogenase, and Rv2626c were associated with active TB, while antibodies to the 16-kDa antigen, ferredoxin A, and ESAT-6 were associated with inactive TB. Thus, the targets of the immune response vary with tuberculosis state. The correlation between bacterial antigen production and infection stage was investigated in mice infected with M. tuberculosis by bacterial transcription profiling. It was found that levels of transcripts encoding the six M. tuberculosis antigens varied during infection. Together, the data indicate that antigen composition of tubercle bacilli varies with stage of infection and that immunoprofiling can distinguish between tuberculosis states.
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Affiliation(s)
- Amy Davidow
- University of Medicine and Dentistry of New Jersey, Newark, USA
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79
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Shi L, Sohaskey CD, Kana BD, Dawes S, North RJ, Mizrahi V, Gennaro ML. Changes in energy metabolism of Mycobacterium tuberculosis in mouse lung and under in vitro conditions affecting aerobic respiration. Proc Natl Acad Sci U S A 2005; 102:15629-34. [PMID: 16227431 PMCID: PMC1255738 DOI: 10.1073/pnas.0507850102] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Indexed: 12/23/2022] Open
Abstract
Transcription profiling of genes encoding components of the respiratory chain and the ATP synthesizing apparatus of Mycobacterium tuberculosis was conducted in vivo in the infected mouse lung, and in vitro in bacterial cultures subjected to gradual oxygen depletion and to nitric oxide treatment. Transcript levels changed dramatically as infection progressed from bacterial exponential multiplication (acute infection) to cessation of bacterial growth (chronic infection) in response to host immunity. The proton-pumping type-I NADH dehydrogenase and the aa3-type cytochrome c oxidase were strongly down-regulated. Concurrently, the less energy-efficient cytochrome bd oxidase was transiently up-regulated. The nitrate transporter NarK2 was also up-regulated, indicative of increased nitrate respiration. The reduced efficiency of the respiratory chain was accompanied by decreased expression of ATP synthesis genes. Thus, adaptation of M. tuberculosis to host immunity involves three successive respiratory states leading to decreased energy production. Decreased bacterial counts in mice infected with a cydC mutant (defective in the cytochrome bd oxidase-associated transporter) at the transition to chronic infection provided initial evidence that the bd oxidase pathway is required for M. tuberculosis adaptation to host immunity. In vitro, NO treatment and hypoxia caused a switch from transcription of type I to type II NADH dehydrogenase. Moreover, cytochrome bd oxidase expression increased, but cytochrome c oxidase expression decreased slightly (nitric oxide) or not at all (hypoxia). These specific differences in respiratory metabolism during M. tuberculosis growth arrest in vitro and in vivo will guide manipulation of in vitro conditions to model bacterial adaptation to host immunity.
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Affiliation(s)
- Lanbo Shi
- Public Health Research Institute, Newark, NJ 07103, USA
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80
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Goh KS, Rastogi N, Berchel M, Huard RC, Sola C. Molecular evolutionary history of tubercle bacilli assessed by study of the polymorphic nucleotide within the nitrate reductase (narGHJI) operon promoter. J Clin Microbiol 2005; 43:4010-4. [PMID: 16081943 PMCID: PMC1233921 DOI: 10.1128/jcm.43.8.4010-4014.2005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A well-characterized collection of Mycobacterium tuberculosis complex (MTC) isolates, representing all known subspecies as well as some relevant genotypic families of M. tuberculosis, was analyzed for the newly discovered narGHJI -215 C-to-T promoter single-nucleotide polymorphism (SNP). This point mutation has been shown in earlier studies to be responsible for the differential nitrate reductase activity of M. tuberculosis versus M. bovis. As previously defined by the presence or the absence of the TbD1 genetic locus, the group included both the "modern" W-Beijing, Haarlem, and Central-Asian1 (CAS1) families as well as the "ancestral" East-African-Indian (EAI) clade. Interestingly, among "modern" M. tuberculosis isolates, those previously classified as Principal Genetic Group 1 (PGG1) organisms by katG463-gyrA95 polymorphism analysis did not present the two-banded narGHJI restriction fragment length polymorphism analysis of PCR products pattern common to the other PGG1 MTC members, including the "ancestral" M. tuberculosis isolates. Instead, they showed a one-banded pattern, aligning them with other evolutionarily recent M. tuberculosis isolates of the PGG2 and PGG3 groups, such as Haarlem, Latin-American and Mediterranean (LAM), and X families. The presence of a nitrate reductase producer phenotype in "Mycobacterium canettii" and some "ancestral" M. tuberculosis isolates, despite a two-band -215C genotype, argues in favor of an alternate mechanism to explain the differential nitrate reductase activity of certain PGG1 subspecies of the MTC. Overall, these findings may help to establish the precise evolutionary history of important genotype families such as W-Beijing and suggest that the -215T genotype may have contributed the virulence, spread, and evolutionary success of "modern" M. tuberculosis strains compared to the remaining MTC organisms.
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Affiliation(s)
- Khye Seng Goh
- Unité de la Tuberculose et des Mycobactéries, Institut Pasteur de Guadeloupe, Pointe-à-Pitre, Guadeloupe, Division of International Medicine and Infectious Diseases, Department of Medicine, Joan and Sanford I. Weill Medical College, Cornell University, New York, New York
| | - Nalin Rastogi
- Unité de la Tuberculose et des Mycobactéries, Institut Pasteur de Guadeloupe, Pointe-à-Pitre, Guadeloupe, Division of International Medicine and Infectious Diseases, Department of Medicine, Joan and Sanford I. Weill Medical College, Cornell University, New York, New York
- Corresponding authors. Mailing address: Institut Pasteur de Guadeloupe, Morne Jolivière, BP484, F97165-Pointe-à-Pitre, Guadeloupe. Phone: 590-590-893881. Fax: 590-590-893880. E-mail for N. Rastogi: . E-mail for C. Sola:
| | - Mylène Berchel
- Unité de la Tuberculose et des Mycobactéries, Institut Pasteur de Guadeloupe, Pointe-à-Pitre, Guadeloupe, Division of International Medicine and Infectious Diseases, Department of Medicine, Joan and Sanford I. Weill Medical College, Cornell University, New York, New York
| | - Richard C. Huard
- Unité de la Tuberculose et des Mycobactéries, Institut Pasteur de Guadeloupe, Pointe-à-Pitre, Guadeloupe, Division of International Medicine and Infectious Diseases, Department of Medicine, Joan and Sanford I. Weill Medical College, Cornell University, New York, New York
| | - Christophe Sola
- Unité de la Tuberculose et des Mycobactéries, Institut Pasteur de Guadeloupe, Pointe-à-Pitre, Guadeloupe, Division of International Medicine and Infectious Diseases, Department of Medicine, Joan and Sanford I. Weill Medical College, Cornell University, New York, New York
- Corresponding authors. Mailing address: Institut Pasteur de Guadeloupe, Morne Jolivière, BP484, F97165-Pointe-à-Pitre, Guadeloupe. Phone: 590-590-893881. Fax: 590-590-893880. E-mail for N. Rastogi: . E-mail for C. Sola:
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81
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Rahman MT, Parreira V, Prescott JF. In vitro and intra-macrophage gene expression by Rhodococcus equi strain 103. Vet Microbiol 2005; 110:131-40. [PMID: 16143469 DOI: 10.1016/j.vetmic.2005.08.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Revised: 07/15/2005] [Accepted: 08/01/2005] [Indexed: 11/30/2022]
Abstract
Rhodococcus equi is a facultative intracellular respiratory pathogen of foals that persists and multiplies within macrophages. In foals, virulence is associated with 80-90 kb plasmids, which include a pathogenicity island (PI) containing the virulence-associated protein (vap) gene family, but detailed understanding of the basis of virulence is still poor. A 60 spot-based DNA microarray was developed containing eight PI genes and 42 chromosomal putative virulence or virulence-associated genes selected from a recent partial genome sequence in order to study transcription of these genes by R. equi grown inside macrophages and under in vitro conditions thought to simulate those of macrophages. In addition to seven PI genes, nine chromosomal genes involved in fatty acid and lipid metabolism (choD, fadD13, fbpB), heme biosynthesis (hemE), iron utilization (mbtF), heat shock resistance and genes encoding chaperones (clpB, groEL), a sigma factor (sigK), and a transcriptional regulator (moxR) were significantly induced in R. equi growing inside macrophages. The pattern of R. equi chromosomal genes significantly transcribed inside macrophages largely differed from those transcribed under in vitro conditions (37 degrees C, pH 5.0 or 50mM H2O2 for 30 min). This study has identified genes, other than those of the virulence plasmid, the transcription of which is enhanced within equine macrophages. These genes should be investigated further to improve understanding of how this organism survives intracellularly.
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Affiliation(s)
- Md Tanvir Rahman
- Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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82
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Korf J, Stoltz A, Verschoor J, De Baetselier P, Grooten J. The Mycobacterium tuberculosis cell wall component mycolic acid elicits pathogen-associated host innate immune responses. Eur J Immunol 2005; 35:890-900. [PMID: 15724242 DOI: 10.1002/eji.200425332] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Recognition of conserved pathogen-associated molecular patterns constitutes a crucial step in the initiation of innate immune responses. We studied the contribution to the host-pathogen interaction of mycolic acid (MA), a major lipid component of the cell envelope of the macrophage intracellular pathogen Mycobacterium tuberculosis and other mycobacteria. MA administered to the peritoneal cavity or to the airways induced a unique macrophage morphotype, similar to the foamy macrophage derivatives observed in tuberculous granulomas and characterized by intracellular accumulation of neutral lipids and entry into mitosis. When assayed for production of inflammatory mediators, a conditioning rather than a direct activation of the MA-elicited foamy macrophages was observed. MA enabled production of IFN-gamma and myeloperoxidase, enhanced TNF-alpha production and suppressed IL-10 upon renewed exposure to innate triggers. Intratracheal instillation of MA mimicked additional features of the airway response to M. tuberculosis infection, namely a rapid but transient neutrophil influx and IL-6 production and a chronic IL-12 production. These MA-elicited cellular innate defenses and the accompanying formation of foamy macrophages identify for the first time the foamy macrophage morphotype as part of the host response to a pathogen-associated structure. Furthermore, these results characterize MA as a direct trigger of innate immunity, distinct from Toll-like receptor ligands.
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Affiliation(s)
- Johanna Korf
- Department of Molecular Biomedical Research, Molecular Immunology Unit, VIB, Ghent University, Ghent, Belgium
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83
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Sambandamurthy VK, Derrick SC, Jalapathy KV, Chen B, Russell RG, Morris SL, Jacobs WR. Long-term protection against tuberculosis following vaccination with a severely attenuated double lysine and pantothenate auxotroph of Mycobacterium tuberculosis. Infect Immun 2005; 73:1196-203. [PMID: 15664964 PMCID: PMC547051 DOI: 10.1128/iai.73.2.1196-1203.2005] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report the safety and immunogenicity of a double lysine and pantothenate auxotroph of Mycobacterium tuberculosis in mice. The DeltalysA DeltapanCD mutant is completely attenuated in immunocompromised SCID and gamma interferon knockout mice yet induces short-term and long-term protection in immunocompetent and CD4-deficient mice following single-dose subcutaneous vaccination.
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84
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Fretin D, Fauconnier A, Köhler S, Halling S, Léonard S, Nijskens C, Ferooz J, Lestrate P, Delrue RM, Danese I, Vandenhaute J, Tibor A, DeBolle X, Letesson JJ. The sheathed flagellum of Brucella melitensis is involved in persistence in a murine model of infection. Cell Microbiol 2005; 7:687-98. [PMID: 15839898 DOI: 10.1111/j.1462-5822.2005.00502.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Persistence infection is the keystone of the ruminant and human diseases called brucellosis and Malta fever, respectively, and is linked to the intracellular tropism of Brucella spp. While described as non-motile, Brucella spp. have all the genes except the chemotactic system, necessary to assemble a functional flagellum. We undertook to determine whether these genes are expressed and are playing a role in some step of the disease process. We demonstrated that in the early log phase of a growth curve in 2YT nutrient broth, Brucella melitensis expresses genes corresponding to the basal (MS ring) and the distal (hook and filament) parts of the flagellar apparatus. Under these conditions, a polar and sheathed flagellar structure is visible by transmission electron microscopy (TEM). We evaluated the effect of mutations in flagellar genes of B. melitensis encoding various parts of the structure, MS ring, P ring, motor protein, secretion apparatus, hook and filament. None of these mutants gave a discernible phenotype as compared with the wild-type strain in cellular models of infection. In contrast, all these mutants were unable to establish a chronic infection in mice infected via the intraperitoneal route, raising the question of the biological role(s) of this flagellar appendage.
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Affiliation(s)
- D Fretin
- Unité de Recherche en Biologie Moléculaire, University of Namur, Belgium
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85
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Abstract
Human tuberculosis is a complex disease caused by bacterial populations that are located in discrete lesions (microenvironments) in a single host. Some of these microenvironments are conducive to replication, whereas others restrict bacterial growth without necessarily sterilizing the infecting microorganisms. The physical and biochemical milieu in these lesions is poorly defined. None of the existing animal models for tuberculosis (except perhaps non-human primates) reproduce the diversity of disease progression that is seen in humans. Nonetheless, transcriptomics and studies using bacterial mutants have led to testable hypotheses about metabolic functions that are essential for viability in the absence of replication. A complete picture of bacterial metabolism must balance reducing equivalents while maintaining an energized membrane and basic cellular processes.
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Affiliation(s)
- Helena I M Boshoff
- Tuberculosis Research Section, LIG/NIAID/NIH, Twinbrook II, Room 239, 12441 Parklawn Drive, Rockville, Maryland 20852, USA.
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86
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Pittman MS, Kelly DJ. Electron transport through nitrate and nitrite reductases in Campylobacter jejuni. Biochem Soc Trans 2005; 33:190-2. [PMID: 15667303 DOI: 10.1042/bst0330190] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Campylobacter jejuni is a small genome pathogen that is incapable of growing strictly anaerobically due to its dependence on an oxygen-requiring ribonucleotide reductase for DNA synthesis. Nevertheless, it has a complex branched respiratory chain, which allows the use of several alternative electron acceptors for growth under oxygen-limited conditions. C. jejuni is equipped with both nitrate reductase (Nap) and nitrite reductase (Nrf) located in the periplasm, each predicted to receive electrons from menaquinol through distinct redox proteins. The pathways of electron transport to nitrate and nitrite are reviewed in this paper. Nitrate is considered as a potential in vivo electron acceptor and a role for nitrite reductase in NO detoxification is suggested.
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Affiliation(s)
- M S Pittman
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
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87
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Benton BM, Zhang JP, Bond S, Pope C, Christian T, Lee L, Winterberg KM, Schmid MB, Buysse JM. Large-scale identification of genes required for full virulence of Staphylococcus aureus. J Bacteriol 2005; 186:8478-89. [PMID: 15576798 PMCID: PMC532413 DOI: 10.1128/jb.186.24.8478-8489.2004] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gene products required for in vivo growth and survival of microbial pathogens comprise a unique functional class and may represent new targets for antimicrobial chemotherapy, vaccine construction, or diagnostics. Although some factors governing Staphylococcus aureus pathogenicity have been identified and studied, a comprehensive genomic analysis of virulence functions will be a prerequisite for developing a global understanding of interactions between this pathogen and its human host. In this study, we describe a genetic screening strategy and demonstrate its use in screening a collection of 6,300 S. aureus insertion mutants for virulence attenuation in a murine model of systemic infection. Ninety-five attenuated mutants were identified, reassembled into new pools, and rescreened using the same murine model. This effort identified 24 highly attenuated mutants, each of which was further characterized for virulence attenuation in vivo and for growth phenotypes in vitro. Mutants were recovered in numbers up to 1,200-fold less than wild type in the spleens of systemically infected animals and up to 4,000-fold less than wild type in localized abscess infections. Genetic analysis of the mutants identified insertions in 23 unique genes. The largest gene classes represented by these mutants encoded enzymes involved in small-molecule biosynthesis and cell surface transmembrane proteins involved in small-molecule binding and transport. Additionally, three insertions defined two histidine kinase sensor-response regulator gene pairs important for S. aureus in vivo survival. Our findings extend the understanding of pathogenic mechanisms employed by S. aureus to ensure its successful growth and survival in vivo. Many of the gene products we have identified represent attractive new targets for antibacterial chemotherapy.
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Affiliation(s)
- Bret M Benton
- Essential Therapeutics, Inc., Mountain View, CA, USA.
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88
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Jacobsen I, Hennig-Pauka I, Baltes N, Trost M, Gerlach GF. Enzymes involved in anaerobic respiration appear to play a role in Actinobacillus pleuropneumoniae virulence. Infect Immun 2005; 73:226-34. [PMID: 15618158 PMCID: PMC538954 DOI: 10.1128/iai.73.1.226-234.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 08/04/2004] [Accepted: 09/03/2004] [Indexed: 11/20/2022] Open
Abstract
Actinobacillus pleuropneumoniae, the etiological agent of porcine pleuropneumonia, is able to survive on respiratory epithelia, in tonsils, and in the anaerobic environment of encapsulated sequesters. It was previously demonstrated that a deletion of the anaerobic dimethyl sulfoxide reductase gene (dmsA) results in attenuation in acute disease (N. Baltes, S. Kyaw, I. Hennig-Pauka, and G. F. Gerlach, Infect. Immun. 71:6784-6792, 2003). In the present study, using two-dimensional polyacrylamide gel electrophoresis and quadrupole time-of-flight mass spectrometry, we identified an aspartate ammonia-lyase (AspA) which is upregulated upon induction with bronchoalveolar lavage fluid (BALF). This enzyme is involved in the production of fumarate, an alternative electron acceptor under anaerobic conditions. The coding gene (aspA) was cloned and shown to be present in all A. pleuropneumoniae serotype reference strains. The transcriptional start point was identified downstream of a putative FNR binding motif, and BALF-dependent activation of aspA was confirmed by construction of an isogenic A. pleuropneumoniae mutant carrying a chromosomal aspA::luxAB transcriptional fusion. Two aspA deletion mutants, A. pleuropneumoniae DeltaaspA and A. pleuropneumoniae DeltaaspADeltadmsA, were constructed, both showing reduced growth under anaerobic conditions in vitro. Pigs challenged with either of the two mutants in an aerosol infection model showed a lower lung lesion score than that of the A. pleuropneumoniae wild-type (wt) controls. Pigs challenged with A. pleuropneumoniae DeltaaspADeltadmsA had a significantly lower clinical score, and this mutant was rarely reisolated from unaltered lung tissue; in contrast, A. pleuropneumoniae DeltaaspA and the A. pleuropneumoniae wt were consistently reisolated in high numbers. These results suggest that enzymes involved in anaerobic respiration are necessary for the pathogen's ability to persist on respiratory tract epithelium and play an important role in A. pleuropneumoniae pathogenesis.
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Affiliation(s)
- Ilse Jacobsen
- Institut für Mikrobiologie, Zentrum für Infektionsmedizin, Stiftung Tierärztliche Hochschule Hannover, Bischofsholer Damm 15, 30173 Hannover, Germany
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89
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Stermann M, Sedlacek L, Maass S, Bange FC. A promoter mutation causes differential nitrate reductase activity of Mycobacterium tuberculosis and Mycobacterium bovis. J Bacteriol 2004; 186:2856-61. [PMID: 15090527 PMCID: PMC387782 DOI: 10.1128/jb.186.9.2856-2861.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The recent publication of the genome sequence of Mycobacterium bovis showed >99.95% identity to M. tuberculosis. No genes unique to M. bovis were found. Instead numerous single-nucleotide polymorphisms (SNPs) were identified. This has led to the hypothesis that differential gene expression due to SNPs might explain the differences between the human and bovine tubercle bacilli. One phenotypic distinction between M. tuberculosis and M. bovis is nitrate reduction, which not only is an essential diagnostic tool but also contributes to mycobacterial pathogenesis. We previously showed that narGHJI encodes a nitrate reductase in both M. tuberculosis and M. bovis and that NarGHJI-mediated nitrate reductase activity was substantially higher in the human tubercle bacillus. In the present study we used a genetic approach to demonstrate that an SNP within the promoter of the nitrate reductase gene cluster narGHJI is responsible for the different nitrate reductase activity of M. tuberculosis and M. bovis. This is the first example of an SNP that leads to differential gene expression between the human and bovine tubercle bacilli.
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Affiliation(s)
- Marion Stermann
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Carl-Neuberg-Strasse 1, 30625 Hanover, Germany
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90
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Kana BD, Mizrahi V. Molecular genetics of Mycobacterium tuberculosis in relation to the discovery of novel drugs and vaccines. Tuberculosis (Edinb) 2004; 84:63-75. [PMID: 14670347 DOI: 10.1016/j.tube.2003.08.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Genetic systems that allow mycobacterial genomes to be mutagenized in a targeted or random fashion have provided the means for developing new tools for the diagnosis, prevention and treatment of tuberculosis by allowing potential targets to be identified and validated. In this review, we highlight key historical developments in the field of mycobacterial genetics, which have yielded the powerful repertoire of genetic tools that are now in hand and provide examples that illustrate their use in exploring specific aspects of mycobacterial metabolism.
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Affiliation(s)
- Bavesh D Kana
- MRC/NHLS/WITS Molecular Mycobacteriology Research Unit, National Health Laboratory Service and School of Pathology, University of the Witwatersrand, NHLS P.O. Box 1038, Room 311 James Gear Building, Johannesburg 2000, South Africa
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91
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Sohaskey CD, Wayne LG. Role of narK2X and narGHJI in hypoxic upregulation of nitrate reduction by Mycobacterium tuberculosis. J Bacteriol 2003; 185:7247-56. [PMID: 14645286 PMCID: PMC296237 DOI: 10.1128/jb.185.24.7247-7256.2003] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2003] [Accepted: 09/25/2003] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis is one of the strongest reducers of nitrate in the genus Mycobacterium: Under microaerobic conditions, whole cells exhibit upregulation of activity, producing approximately eightfold more nitrite than those of aerobic cultures of the same age. Assays of cell extracts from aerobic cultures and hypoxic cultures yielded comparable nitrate reductase activities. Mycobacterium bovis produced only low levels of nitrite, and this activity was not induced by hypoxia. M. tuberculosis has two sets of genes, narGHJI and narX of the narK2X operon, that exhibit some degree of homology to prokaryotic dissimilatory nitrate reductases. Each of these were knocked out by insertional inactivation. The narG mutant showed no nitrate reductase activity in whole culture or in cell-free assays, while the narX mutant showed wild-type levels in both assays. A knockout of the putative nitrite transporter narK2 gene produced a strain that had aerobic levels of nitrate reductase activity but failed to show hypoxic upregulation. Insertion of the M. tuberculosis narGHJI into a nitrate reductase Escherichia coli mutant allowed anaerobic growth in the presence of nitrate. Under aerobic and hypoxic conditions, transcription of narGHJI was constitutive, while the narK2X operon was induced under hypoxia, as measured with a lacZ reporter system and by quantitative real-time reverse PCR. This indicates that nitrate reductase activity in M. tuberculosis is due to the narGHJI locus with no detectable contribution from narX and that the hypoxic upregulation of activity is associated with the induction of the nitrate and nitrite transport gene narK2.
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Affiliation(s)
- Charles D Sohaskey
- Department of Veterans Affairs Medical Center, Long Beach,and Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, USA.
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92
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Baltes N, Hennig-Pauka I, Jacobsen I, Gruber AD, Gerlach GF. Identification of dimethyl sulfoxide reductase in Actinobacillus pleuropneumoniae and its role in infection. Infect Immun 2003; 71:6784-92. [PMID: 14638764 PMCID: PMC308893 DOI: 10.1128/iai.71.12.6784-6792.2003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2003] [Revised: 06/24/2003] [Accepted: 09/03/2003] [Indexed: 11/20/2022] Open
Abstract
Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, is capable of persisting in oxygen-deprived surroundings, namely, tonsils and sequestered necrotic lung tissue. Utilization of alternative terminal electron acceptors in the absence of oxygen is a common strategy in bacteria under anaerobic growth conditions. In an experiment aimed at identification of genes expressed in vivo, the putative catalytic subunit DmsA of anaerobic dimethyl sulfoxide reductase was identified in an A. pleuropneumoniae serotype 7 strain. The 90-kDa protein exhibits 85% identity to the putative DmsA protein of Haemophilus influenzae, and its expression was found to be upregulated under anaerobic conditions. Analysis of the unfinished A. pleuropneumoniae genome sequence revealed putative open reading frames (ORFs) encoding DmsB and DmsC proteins situated downstream of the dmsA ORF. In order to investigate the role of the A. pleuropneumoniae DmsA protein in virulence, an isogenic deletion mutant, A. pleuropneumoniae DeltadmsA, was constructed and examined in an aerosol infection model. A. pleuropneumoniae DeltadmsA was attenuated in acute disease, which suggests that genes involved in oxidative metabolism under anaerobic conditions might contribute significantly to A. pleuropneumoniae virulence.
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Affiliation(s)
- Nina Baltes
- Department of Infectious Diseases, Institute for Microbiology, Veterinary School of Hannover, Germany.
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93
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Ohno H, Zhu G, Mohan VP, Chu D, Kohno S, Jacobs WR, Chan J. The effects of reactive nitrogen intermediates on gene expression in Mycobacterium tuberculosis. Cell Microbiol 2003; 5:637-48. [PMID: 12925133 DOI: 10.1046/j.1462-5822.2003.00307.x] [Citation(s) in RCA: 159] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nitric oxide (NO) and related reactive nitrogen intermediates (RNI) are effective antimycobacterial agents and signal-transducing molecules. The present study uses microarray analysis to examine the effects of RNI on Mycobacterium tuberculosis gene expression. A common set of 53 genes was regulated by two chemically distinct nitric oxide donors. For a subset of the RNI-inducible genes, evidence exists suggesting that they may play a role in promoting survival of the tubercle bacillus in the host. Results obtained from studies based on a murine experimental tuberculosis model involving nos2-deficient mice suggest that RNI could regulate M. tuberculosis gene expression in vivo. Finally, there is a remarkable overlap between the RNI-inducible regulon and that previously reported to be regulated by hypoxia; and both reactive nitrogen species and anaerobicity upregulate the expression of one and the same putative two-component regulatory response system. Together, the results of this study provide evidence suggesting that (i) RNI play a role in regulating M. tuberculosis gene expression in vivo; (ii) the reactive nitrogen species upregulate genes that may be conducive to the survival of the tubercle bacillus in the infected host; and (iii) RNI and hypoxia may regulate mycobacterial gene expression via overlapping signal transduction pathways.
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Affiliation(s)
- Hideaki Ohno
- Departments of Medicine and Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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94
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Dahl JL, Kraus CN, Boshoff HIM, Doan B, Foley K, Avarbock D, Kaplan G, Mizrahi V, Rubin H, Barry CE. The role of RelMtb-mediated adaptation to stationary phase in long-term persistence of Mycobacterium tuberculosis in mice. Proc Natl Acad Sci U S A 2003; 100:10026-31. [PMID: 12897239 PMCID: PMC187750 DOI: 10.1073/pnas.1631248100] [Citation(s) in RCA: 258] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Long-term survival of nonreplicating Mycobacterium tuberculosis (Mtb) is ensured by the coordinated shutdown of active metabolism through a broad transcriptional program called the stringent response. In Mtb, this response is initiated by the enzymatic action of RelMtb and deletion of relMtb produces a strain (H37RvDeltarelMtb) severely compromised in the maintenance of long-term viability. Although aerosol inoculation of mice with H37RvDeltarelMtb results in normal initial bacterial growth and containment, the ability of this strain to sustain chronic infection is severely impaired. Significant histopathologic differences were noted in lungs and spleens of mice infected with H37RvDeltarelMtb compared with controls throughout the course of the infection. Microarray analysis revealed that H37RvDeltarelMtb suffers from a generalized alteration of the transcriptional apparatus, as well as specific changes in the expression of virulence factors, cell-wall biosynthetic enzymes, heat shock proteins, and secreted antigens that may alter immune recognition of the recombinant organism. Thus, RelMtb is critical for the successful establishment of persistent infection in mice by altering the expression of antigenic and enzymatic factors that may contribute to successful latent infection.
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Affiliation(s)
- John L Dahl
- Tuberculosis Research Section, National Institute of Allergy and Infectious Disease, 12441 Parklawn Drive, Rockville, MD 20852, USA
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95
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Stermann M, Bohrssen A, Diephaus C, Maass S, Bange FC. Polymorphic nucleotide within the promoter of nitrate reductase (NarGHJI) is specific for Mycobacterium tuberculosis. J Clin Microbiol 2003; 41:3252-9. [PMID: 12843072 PMCID: PMC165301 DOI: 10.1128/jcm.41.7.3252-3259.2003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis rapidly reduces nitrate, leading to the accumulation of nitrite. This characteristic served for the past 40 years to differentiate M. tuberculosis from other members of the Mycobacterium tuberculosis complex (MTBC), such as Mycobacterium bovis (non-BCG [referred to here as simply "M. bovis"]), Mycobacterium bovis BCG, Mycobacterium africanum, or Mycobacterium microti. Here, a narG deletion in M. tuberculosis showed that rapid nitrite accumulation of M. tuberculosis is mediated by narGHJI. Analysis of narG mutants of M. bovis and M. bovis BCG showed that, as in M. tuberculosis, nitrite accumulation was mediated by narGHJI, and no other nitrate reductase was involved. However, in contrast to M. tuberculosis, accumulation was delayed for several days. Comparison of the narGHJI promoter revealed that, at nucleotide -215 prior to the start codon of narG, M. tuberculosis carried a thymine residue, whereas the bovine mycobacteria carried a cytosine residue. Using LightCycler technology we examined 62 strains of M. tuberculosis, M. bovis, M. bovis BCG, M. microti, and M. africanum and demonstrated that this single nucleotide polymorphism was specific for M. tuberculosis. For further differentiation within the MTBC, we included, by using LightCycler technology, the previously described analysis of oxyR polymorphism, which is specific for the bovine mycobacteria, and the RD1 polymorphism, which is specific for M. bovis BCG. Based on these results, we suggest a LightCycler format for rapid and unambiguous diagnosis of M. tuberculosis, M. bovis, and M. bovis BCG.
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Affiliation(s)
- Marion Stermann
- Department of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, 30625 Hannover, Germany
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96
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Rahman MT, Herron LL, Kapur V, Meijer WG, Byrne BA, Ren J, Nicholson VM, Prescott JF. Partial genome sequencing of Rhodococcus equi ATCC 33701. Vet Microbiol 2003; 94:143-58. [PMID: 12781482 DOI: 10.1016/s0378-1135(03)00100-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Preliminary analysis of a partial (30% coverage) genome sequence of Rhodococcus equi has revealed a number of important features. The most notable was the extent of the homology of genes identified with those of Mycobacterium tuberculosis. The similarities in the proportion of genes devoted to fatty acid degradation and to lipid biosynthesis was a striking but not surprising finding given the relatedness of these organisms and their success as intracellular pathogens. The rapid recent improvement in understanding of virulence in M. tuberculosis and other pathogenic mycobacteria has identified a large number of genes of putative or proven importance in virulence, homologs of many of which were also identified in R. equi. Although R. equi appears to have currently unique genes, and has important differences, its similarity to M. tuberculosis supports the need to understand the basis of virulence in this organism. The partial genome sequence will be a resource for workers interested in R. equi until such time as a full genome sequence has been characterized.
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Affiliation(s)
- M T Rahman
- Department of Pathobiology, University of Guelph, Guelph, Ont. N1G 2W1, Canada
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97
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Abstract
Tuberculosis (TB), one of the oldest known human diseases. is still is one of the major causes of mortality, since two million people die each year from this malady. TB has many manifestations, affecting bone, the central nervous system, and many other organ systems, but it is primarily a pulmonary disease that is initiated by the deposition of Mycobacterium tuberculosis, contained in aerosol droplets, onto lung alveolar surfaces. From this point, the progression of the disease can have several outcomes, determined largely by the response of the host immune system. The efficacy of this response is affected by intrinsic factors such as the genetics of the immune system as well as extrinsic factors, e.g., insults to the immune system and the nutritional and physiological state of the host. In addition, the pathogen may play a role in disease progression since some M. tuberculosis strains are reportedly more virulent than others, as defined by increased transmissibility as well as being associated with higher morbidity and mortality in infected individuals. Despite the widespread use of an attenuated live vaccine and several antibiotics, there is more TB than ever before, requiring new vaccines and drugs and more specific and rapid diagnostics. Researchers are utilizing information obtained from the complete sequence of the M. tuberculosis genome and from new genetic and physiological methods to identify targets in M. tuberculosis that will aid in the development of these sorely needed antitubercular agents.
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Affiliation(s)
- Issar Smith
- TB Center, Public Health Research Institute, International Center for Public Health, Newark, New Jersey 07103-3535, USA.
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98
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Garnier T, Eiglmeier K, Camus JC, Medina N, Mansoor H, Pryor M, Duthoy S, Grondin S, Lacroix C, Monsempe C, Simon S, Harris B, Atkin R, Doggett J, Mayes R, Keating L, Wheeler PR, Parkhill J, Barrell BG, Cole ST, Gordon SV, Hewinson RG. The complete genome sequence of Mycobacterium bovis. Proc Natl Acad Sci U S A 2003; 100:7877-82. [PMID: 12788972 PMCID: PMC164681 DOI: 10.1073/pnas.1130426100] [Citation(s) in RCA: 653] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2003] [Accepted: 03/19/2003] [Indexed: 11/18/2022] Open
Abstract
Mycobacterium bovis is the causative agent of tuberculosis in a range of animal species and man, with worldwide annual losses to agriculture of $3 billion. The human burden of tuberculosis caused by the bovine tubercle bacillus is still largely unknown. M. bovis was also the progenitor for the M. bovis bacillus Calmette-Guérin vaccine strain, the most widely used human vaccine. Here we describe the 4,345,492-bp genome sequence of M. bovis AF2122/97 and its comparison with the genomes of Mycobacterium tuberculosis and Mycobacterium leprae. Strikingly, the genome sequence of M. bovis is >99.95% identical to that of M. tuberculosis, but deletion of genetic information has led to a reduced genome size. Comparison with M. leprae reveals a number of common gene losses, suggesting the removal of functional redundancy. Cell wall components and secreted proteins show the greatest variation, indicating their potential role in host-bacillus interactions or immune evasion. Furthermore, there are no genes unique to M. bovis, implying that differential gene expression may be the key to the host tropisms of human and bovine bacilli. The genome sequence therefore offers major insight on the evolution, host preference, and pathobiology of M. bovis.
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Affiliation(s)
- Thierry Garnier
- Unité de Génétique Moléculaire Bactérienne and PT4 Annotation, Génopole, Institut Pasteur, 28 Rue du Docteur Roux, 75724 Paris Cedex 15, France
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99
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Cox RA. Correlation of the rate of protein synthesis and the third power of the RNA : protein ratio in Escherichia coli and Mycobacterium tuberculosis. MICROBIOLOGY (READING, ENGLAND) 2003; 149:729-737. [PMID: 12634341 DOI: 10.1099/mic.0.25645-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In order to further understand the different physiological states of the tubercle bacillus, a frame of reference was sought by first correlating the macromolecular compositions of Escherichia coli with specific growth rates and also with the rates of protein synthesis. Data for DNA : protein : RNA were converted to the average amounts of DNA [m(DNA(av))], protein [m(p(av))] and RNA [m(RNA(av))] per cell. The specific growth rate micro was found to be directly proportional to m(RNA(av))/m(p(av)). The specific protein synthesis rate per average cell [omega(p(av))] was shown to be directly proportional to the third power of the ratio m(RNA(av))/m(p(av)) which reflects the ribosome concentration. The equations derived were shown apply to both E. coli ( micro =1.73 h(-1)) and Mycobacterium bovis BCG ( micro =0.029 h(-1)).
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Affiliation(s)
- Robert A Cox
- Division of Mycobacterial Research, National Institute for Medical Research, London NW7 1AA, UK
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100
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Abstract
Obligately aerobic tubercle bacilli are capable of adapting to survive hypoxia by developing into a nonreplicating or dormant form. Dormant bacilli maintain viability for extended periods. Furthermore, they are resistant to antimycobacterials, and hence, dormancy might play a role in the persistence of tuberculosis infection despite prolonged chemotherapy. Previously, we have grown dormant Mycobacterium bovis BCG in an oxygen-limited Wayne culture system and subjected the bacilli to proteome analysis. This work revealed the upregulation of the response regulator Rv3133c and three other polypeptides (alpha-crystallin and two "conserved hypothetical" proteins) upon entry into dormancy. Here, we replaced the coding sequence of the response regulator with a kanamycin resistance cassette and demonstrated that the loss-of-function mutant died after oxygen starvation-induced termination of growth. Thus, the disruption of this dormancy-induced transcription factor resulted in loss of the ability of BCG to adapt to survival of hypoxia. Two-dimensional gel electrophoresis of protein extracts from the gene-disrupted strain showed that the genetic loss of the response regulator caused loss of the induction of the other three dormancy proteins. Thus, the upregulation of these dormancy proteins requires the response regulator. Based on these two functions, dormancy survival and regulation, we named the Rv3133c gene dosR for dormancy survival regulator. Our results provide conclusive evidence that DosR is a key regulator in the oxygen starvation-induced mycobacterial dormancy response.
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Affiliation(s)
- Calvin Boon
- Mycobacterium Biology Laboratory, Institute of Molecular and Cell Biology, Singapore 117609, Republic of Singapore
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