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PCR-based screening of targeted mutants for the fast and simultaneous identification of bacterial virulence factors. Biotechniques 2012; 53:000113906. [PMID: 26307257 DOI: 10.2144/000113906] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 07/03/2012] [Indexed: 11/23/2022] Open
Abstract
Understanding the strategies used by pathogens to infect, survive, and proliferate in their hosts requires the identification of virulence factors. We developed PCR-based screening of targeted mutants to facilitate quick, simultaneous detection of multiple novel bacterial virulence genes. Based on direct PCR screening of pooled targeted mutants, this approach provides a fast and sensitive measure of virulence attenuation while significantly reducing the number of animals and time required. We demonstrate that the careful design of gene-specific primers allows the direct relative quantification of mixed mutants in infected mouse organs. Indeed, we show that the band intensity of the PCR product is directly related to the quantity of the corresponding strain in a pool of mutants. We applied the PCR-based screening of targeted mutants to the murine model of listeriosis and revealed new genes required for full pathogenicity of Listeria monocytogenes, a facultative human intracellular pathogen. PCR-based screening is a simple, useful, and fast technique to test pools of targeted bacterial mutants in vivo, without the requirements for a rigorous purification step, complicated PCR set-up, or special equipment. This approach can be adapted to other bacterial systems, constituting a significant advance in the field of infection biology.
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52
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Ehrt S, Rhee K. Mycobacterium tuberculosis metabolism and host interaction: mysteries and paradoxes. Curr Top Microbiol Immunol 2012; 374:163-88. [PMID: 23242856 DOI: 10.1007/82_2012_299] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Metabolism is a widely recognized facet of all host-pathogen interactions. Knowledge of its roles in pathogenesis, however, remains comparatively incomplete. Existing studies have emphasized metabolism as a cell autonomous property of pathogens used to fuel replication in a quantitative, rather than qualitatively specific, manner. For Mycobacterium tuberculosis, however, matters could not be more different. M. tuberculosis is a chronic facultative intracellular pathogen that resides in humans as its only known host. Within humans, M. tuberculosis resides chiefly within the macrophage phagosome, the cell type, and compartment most committed to its eradication. M. tuberculosis has thus evolved its metabolic network to both maintain and propagate its survival as a species within a single host. The specific ways in which its metabolic network serves these distinct, through interdependent, functions, however, remain incompletely defined. Here, we review existing knowledge of the M. tuberculosis-host interaction, highlighting the distinct phases of its natural life cycle and the diverse microenvironments encountered therein.
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Affiliation(s)
- Sabine Ehrt
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, 10065, USA,
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53
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de la Paz Santangelo M, Gest PM, Guerin ME, Coinçon M, Pham H, Ryan G, Puckett SE, Spencer JS, Gonzalez-Juarrero M, Daher R, Lenaerts AJ, Schnappinger D, Therisod M, Ehrt S, Sygusch J, Jackson M. Glycolytic and non-glycolytic functions of Mycobacterium tuberculosis fructose-1,6-bisphosphate aldolase, an essential enzyme produced by replicating and non-replicating bacilli. J Biol Chem 2011; 286:40219-31. [PMID: 21949126 PMCID: PMC3220552 DOI: 10.1074/jbc.m111.259440] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 09/09/2011] [Indexed: 12/29/2022] Open
Abstract
The search for antituberculosis drugs active against persistent bacilli has led to our interest in metallodependent class II fructose-1,6-bisphosphate aldolase (FBA-tb), a key enzyme of gluconeogenesis absent from mammalian cells. Knock-out experiments at the fba-tb locus indicated that this gene is required for the growth of Mycobacterium tuberculosis on gluconeogenetic substrates and in glucose-containing medium. Surface labeling and enzymatic activity measurements revealed that this enzyme was exported to the cell surface of M. tuberculosis and produced under various axenic growth conditions including oxygen depletion and hence by non-replicating bacilli. Importantly, FBA-tb was also produced in vivo in the lungs of infected guinea pigs and mice. FBA-tb bound human plasmin(ogen) and protected FBA-tb-bound plasmin from regulation by α(2)-antiplasmin, suggestive of an involvement of this enzyme in host/pathogen interactions. The crystal structures of FBA-tb in the native form and in complex with a hydroxamate substrate analog were determined to 2.35- and 1.9-Å resolution, respectively. Whereas inhibitor attachment had no effect on the plasminogen binding activity of FBA-tb, it competed with the natural substrate of the enzyme, fructose 1,6-bisphosphate, and substantiated a previously unknown reaction mechanism associated with metallodependent aldolases involving recruitment of the catalytic zinc ion by the substrate upon active site binding. Altogether, our results highlight the potential of FBA-tb as a novel therapeutic target against both replicating and non-replicating bacilli.
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Affiliation(s)
- Maria de la Paz Santangelo
- From the Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
- Instituto de Biotecnología, Centro de Investigación en Ciencias Veterinarias y Agronómicas-Instituto Nacional de Tecnología Agropecuaria, 1686 Buenos Aires, Argentina
| | - Petra M. Gest
- From the Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
| | - Marcelo E. Guerin
- Unidad de Biofísica, Centro Mixto Consejo Superior de Investigaciones Científicas-Universidad del País Vasco/Euskal Herriko Unibertsitatea (CSIC-UPV/EHU), Barrio Sarriena s/n, Leioa, 48940 Bizkaia, Spain
- Departamento de Bioquímica, Universidad del País Vasco, Aptdo. 644, 48080 Bilbao, Spain
- IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
| | - Mathieu Coinçon
- Département de Biochimie, Université de Montréal, CP 6128, Station centre-ville, Montréal PQ H3C 3J7, Canada
| | - Ha Pham
- From the Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
| | - Gavin Ryan
- From the Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
| | - Susan E. Puckett
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York 10065
| | - John S. Spencer
- From the Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
| | - Mercedes Gonzalez-Juarrero
- From the Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
| | - Racha Daher
- Laboratoire de Chimie Bioorganique et Bioinorganique-Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182, Université Paris Sud, 91405 Orsay, France and
| | - Anne J. Lenaerts
- From the Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
| | - Dirk Schnappinger
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York 10065
| | - Michel Therisod
- Laboratoire de Chimie Bioorganique et Bioinorganique-Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182, Université Paris Sud, 91405 Orsay, France and
| | - Sabine Ehrt
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York 10065
| | - Jurgen Sygusch
- Département de Biochimie, Université de Montréal, CP 6128, Station centre-ville, Montréal PQ H3C 3J7, Canada
| | - Mary Jackson
- From the Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682
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Woong Park S, Klotzsche M, Wilson DJ, Boshoff HI, Eoh H, Manjunatha U, Blumenthal A, Rhee K, Barry CE, Aldrich CC, Ehrt S, Schnappinger D. Evaluating the sensitivity of Mycobacterium tuberculosis to biotin deprivation using regulated gene expression. PLoS Pathog 2011; 7:e1002264. [PMID: 21980288 PMCID: PMC3182931 DOI: 10.1371/journal.ppat.1002264] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2011] [Accepted: 07/28/2011] [Indexed: 12/04/2022] Open
Abstract
In the search for new drug targets, we evaluated the biotin synthetic pathway of Mycobacterium tuberculosis (Mtb) and constructed an Mtb mutant lacking the biotin biosynthetic enzyme 7,8-diaminopelargonic acid synthase, BioA. In biotin-free synthetic media, ΔbioA did not produce wild-type levels of biotinylated proteins, and therefore did not grow and lost viability. ΔbioA was also unable to establish infection in mice. Conditionally-regulated knockdown strains of Mtb similarly exhibited impaired bacterial growth and viability in vitro and in mice, irrespective of the timing of transcriptional silencing. Biochemical studies further showed that BioA activity has to be reduced by approximately 99% to prevent growth. These studies thus establish that de novo biotin synthesis is essential for Mtb to establish and maintain a chronic infection in a murine model of TB. Moreover, these studies provide an experimental strategy to systematically rank the in vivo value of potential drug targets in Mtb and other pathogens. We evaluated the biotin synthetic pathway of Mycobacterium tuberculosis (Mtb) as a new drug target by first generating an Mtb deletion mutant, ΔbioA, in which the biotin biosynthetic enzyme 7,8-diaminopelargonic acid synthase (BioA) has been inactivated. This mutant grew in the presence of biotin or des-thiobiotin, but not with an intermediate of the biotin biosynthesis pathway that requires BioA to be converted into biotin. Without exogenous biotin or des-thiobiotin, ΔbioA, was unable to produce biotinylated proteins, which are required for the biosynthesis of fatty acids, and thus died in biotin-free media. Using a regulatable promoter and different ribosome binding sequences we next constructed tightly controlled TetON mutants, in which expression of BioA could be induced with tetracyclines, but was inhibited in their absence. Characterization of these mutants during infections demonstrated that de novo biotin synthesis is not only required to establish infections but also to maintain bacterial persistence. Inhibition of BioA or other enzymes of the biotin biosynthesis pathways could thus be used to kill Mtb during both acute and chronic infections. Biochemical and immunological analyses of different Mtb mutants indicate that drugs targeting BioA would have to inactive approximately 99% of its activity to be effective.
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Affiliation(s)
- Sae Woong Park
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| | - Marcus Klotzsche
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| | - Daniel J. Wilson
- Center for Drug Design, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Helena I. Boshoff
- Tuberculosis Research Section, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, United States of America
| | - Hyungjin Eoh
- Department of Medicine, Weill Cornell Medical College, New York, New York, United States of America
| | | | - Antje Blumenthal
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| | - Kyu Rhee
- Department of Medicine, Weill Cornell Medical College, New York, New York, United States of America
| | - Clifton E. Barry
- Tuberculosis Research Section, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, United States of America
| | - Courtney C. Aldrich
- Center for Drug Design, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Sabine Ehrt
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail: (SE); (DS)
| | - Dirk Schnappinger
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail: (SE); (DS)
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Central carbon metabolism in Mycobacterium tuberculosis: an unexpected frontier. Trends Microbiol 2011; 19:307-14. [PMID: 21561773 DOI: 10.1016/j.tim.2011.03.008] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 03/29/2011] [Accepted: 03/31/2011] [Indexed: 11/23/2022]
Abstract
Recent advances in liquid chromatography and mass spectrometry have enabled the highly parallel, quantitative measurement of metabolites within a cell and the ability to trace their biochemical fates. In Mycobacterium tuberculosis (Mtb), these advances have highlighted major gaps in our understanding of central carbon metabolism (CCM) that have prompted fresh interpretations of the composition and structure of its metabolic pathways and the phenotypes of Mtb strains in which CCM genes have been deleted. High-throughput screens have demonstrated that small chemical compounds can selectively inhibit some enzymes of Mtb's CCM while sparing homologs in the host. Mtb's CCM has thus emerged as a frontier for both fundamental and translational research.
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