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Arginine-deprivation-induced oxidative damage sterilizes Mycobacterium tuberculosis. Proc Natl Acad Sci U S A 2018; 115:9779-9784. [PMID: 30143580 PMCID: PMC6166831 DOI: 10.1073/pnas.1808874115] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Reactive oxygen species (ROS)-mediated oxidative stress and DNA damage have recently been recognized as contributing to the efficacy of most bactericidal antibiotics, irrespective of their primary macromolecular targets. Inhibitors of targets involved in both combating oxidative stress as well as being required for in vivo survival may exhibit powerful synergistic action. This study demonstrates that the de novo arginine biosynthetic pathway in Mycobacterium tuberculosis (Mtb) is up-regulated in the early response to the oxidative stress-elevating agent isoniazid or vitamin C. Arginine deprivation rapidly sterilizes the Mtb de novo arginine biosynthesis pathway mutants ΔargB and ΔargF without the emergence of suppressor mutants in vitro as well as in vivo. Transcriptomic and flow cytometry studies of arginine-deprived Mtb have indicated accumulation of ROS and extensive DNA damage. Metabolomics studies following arginine deprivation have revealed that these cells experienced depletion of antioxidant thiols and accumulation of the upstream metabolite substrate of ArgB or ArgF enzymes. ΔargB and ΔargF were unable to scavenge host arginine and were quickly cleared from both immunocompetent and immunocompromised mice. In summary, our investigation revealed in vivo essentiality of the de novo arginine biosynthesis pathway for Mtb and a promising drug target space for combating tuberculosis.
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Abstract
Cell elongation occurs primarily at the mycobacterial cell poles, but the molecular mechanisms governing this spatial regulation remain elusive. We recently reported the presence of an intracellular membrane domain (IMD) that was spatially segregated from the conventional plasma membrane in Mycobacterium smegmatis. The IMD is enriched in the polar region of actively elongating cells and houses many essential enzymes involved in envelope biosynthesis, suggesting its role in spatially restricted elongation at the cell poles. Here, we examined reorganization of the IMD when the cells are no longer elongating. To monitor the IMD, we used a previously established reporter strain expressing fluorescent IMD markers and grew it to the stationary growth phase or exposed the cells to nutrient starvation. In both cases, the IMD was delocalized from the cell pole and distributed along the sidewall. Importantly, the IMD could still be isolated biochemically by density gradient fractionation, indicating its maintenance as a membrane domain. Chemical and genetic inhibition of peptidoglycan biosynthesis led to the delocalization of the IMD, suggesting the suppression of peptidoglycan biosynthesis as a trigger of spatial IMD rearrangement. Starved cells with a delocalized IMD can resume growth upon nutrient repletion, and polar enrichment of the IMD coincides with the initiation of cell elongation. These data reveal that the IMD is a membrane domain with the unprecedented capability of subcellular repositioning in response to the physiological conditions of the mycobacterial cell. Mycobacteria include medically important species, such as the human tuberculosis pathogen Mycobacterium tuberculosis. The highly impermeable cell envelope is a hallmark of these microbes, and its biosynthesis is a proven chemotherapeutic target. Despite the accumulating knowledge regarding the biosynthesis of individual envelope components, the regulatory mechanisms behind the coordinated synthesis of the complex cell envelope remain elusive. We previously reported the presence of a metabolically active membrane domain enriched in the elongating poles of actively growing mycobacteria. However, the spatiotemporal dynamics of the membrane domain in response to stress have not been examined. Here, we show that the membrane domain is spatially reorganized when growth is inhibited in the stationary growth phase, under nutrient starvation, or in response to perturbation of peptidoglycan biosynthesis. Our results suggest that mycobacteria have a mechanism to spatiotemporally coordinate the membrane domain in response to metabolic needs under different growth conditions.
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Abstract
The complex cell envelope is a hallmark of mycobacteria and is anchored by the peptidoglycan layer, which is similar to that of Escherichia coli and a number of other bacteria but with modifications to the monomeric units and other structural complexities that are likely related to a role for the peptidoglycan in stabilizing the mycolyl-arabinogalactan-peptidoglycan complex (MAPc). In this article, we will review the genetics of several aspects of peptidoglycan biosynthesis in mycobacteria, including the production of monomeric precursors in the cytoplasm, assembly of the monomers into the mature wall, cell wall turnover, and cell division. Finally, we will touch upon the resistance of mycobacteria to β-lactam antibiotics, an important class of drugs that, until recently, have not been extensively exploited as potential antimycobacterial agents. We will also note areas of research where there are still unanswered questions.
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Evans G, Schuldt L, Griffin MDW, Devenish SRA, Grant Pearce F, Perugini MA, Dobson RCJ, Jameson GB, Weiss MS, Gerrard JA. A tetrameric structure is not essential for activity in dihydrodipicolinate synthase (DHDPS) from Mycobacterium tuberculosis. Arch Biochem Biophys 2011; 512:154-9. [PMID: 21672512 DOI: 10.1016/j.abb.2011.05.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 05/19/2011] [Accepted: 05/20/2011] [Indexed: 11/19/2022]
Abstract
Dihydrodipicolinate synthase (DHDPS) is a validated antibiotic target for which a new approach to inhibitor design has been proposed: disrupting native tetramer formation by targeting the dimer-dimer interface. In this study, rational design afforded a variant of Mycobacterium tuberculosis, Mtb-DHDPS-A204R, with disrupted quaternary structure. X-ray crystallography (at a resolution of 2.1Å) revealed a dimeric protein with an identical fold and active-site structure to the tetrameric wild-type enzyme. Analytical ultracentrifugation confirmed the dimeric structure in solution, yet the dimeric mutant has similar activity to the wild-type enzyme. Although the affinity for both substrates was somewhat decreased, the high catalytic competency of the enzyme was surprising in the light of previous results showing that dimeric variants of the Escherichia coli and Bacillus anthracis DHDPS enzymes have dramatically reduced activity compared to their wild-type tetrameric counterparts. These results suggest that Mtb-DHDPS-A204R is similar to the natively dimeric enzyme from Staphylococcus aureus, and highlight our incomplete understanding of the role played by oligomerisation in relating protein structure and function.
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Affiliation(s)
- Genevieve Evans
- Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
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Hinchey J, Jeon BY, Alley H, Chen B, Goldberg M, Derrick S, Morris S, Jacobs WR, Porcelli SA, Lee S. Lysine auxotrophy combined with deletion of the SecA2 gene results in a safe and highly immunogenic candidate live attenuated vaccine for tuberculosis. PLoS One 2011; 6:e15857. [PMID: 21264335 PMCID: PMC3018466 DOI: 10.1371/journal.pone.0015857] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 11/26/2010] [Indexed: 11/18/2022] Open
Abstract
Tuberculosis (TB) caused by Mycobacterium tuberculosis remains a major global health problem, despite the widespread use of the M. bovis Bacille Calmette-Guerin (BCG) vaccine and the availability of drug therapies. In recent years, the high incidence of coinfection of M. tuberculosis and HIV, as well as escalating problems associated with drug resistance, has raised ominous concerns with regard to TB control. Vaccination with BCG has not proven highly effective in controlling TB, and also has been associated with increasing concerns about the potential for the vaccine to cause disseminated mycobacterial infection in HIV infected hosts. Thus, the development of an efficacious and safe TB vaccine is generally viewed as a critical to achieving control of the ongoing global TB pandemic. In the current study, we have analyzed the vaccine efficacy of an attenuated M. tuberculosis strain that combines a mutation that enhances T cell priming (ΔsecA2) with a strongly attenuating lysine auxotrophy mutation (ΔlysA). The ΔsecA2 mutant was previously shown to be defective in the inhibition of apoptosis and markedly increased priming of antigen-specific CD8+ T cells in vivo. Similarly, the ΔsecA2ΔlysA strain retained enhanced apoptosis and augmented CD8+ T cell stimulatory effects, but with a noticeably improved safety profile in immunosuppressed mice. Thus, the M. tuberculosis ΔsecA2ΔlysA mutant represents a live attenuated TB vaccine strain with the potential to deliver increased protection and safety compared to standard BCG vaccination.
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Affiliation(s)
- Joseph Hinchey
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Bo Y. Jeon
- Department of Microbiology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Holly Alley
- Duke Human Vaccine Institute, Durham, North Carolina, United States of America
| | - Bing Chen
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Michael Goldberg
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Steven Derrick
- Center for Biologics Evaluation, US Food and Drug Administration, Bethesda, Maryland, United States of America
| | - Sheldon Morris
- Center for Biologics Evaluation, US Food and Drug Administration, Bethesda, Maryland, United States of America
| | - William R. Jacobs
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Steven A. Porcelli
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Sunhee Lee
- Duke Human Vaccine Institute, Durham, North Carolina, United States of America
- * E-mail:
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Flores AR, Parsons LM, Pavelka MS. Genetic analysis of the beta-lactamases of Mycobacterium tuberculosis and Mycobacterium smegmatis and susceptibility to beta-lactam antibiotics. MICROBIOLOGY-SGM 2005; 151:521-532. [PMID: 15699201 DOI: 10.1099/mic.0.27629-0] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Mycobacteria produce beta-lactamases and are intrinsically resistant to beta-lactam antibiotics. In addition to the beta-lactamases, cell envelope permeability and variations in certain peptidoglycan biosynthetic enzymes are believed to contribute to beta-lactam resistance in these organisms. To allow the study of these additional mechanisms, mutants of the major beta-lactamases, BlaC and BlaS, were generated in the pathogenic Mycobacterium tuberculosis strain H37Rv and the model organism Mycobacterium smegmatis strain PM274. The mutants M. tuberculosis PM638 (DeltablaC1) and M. smegmatis PM759 (DeltablaS1) showed an increase in susceptibility to beta-lactam antibiotics, as determined by disc diffusion and minimal inhibitory concentration (MIC) assays. The susceptibility of the mutants, as assayed by disc diffusion tests, to penicillin-type beta-lactam antibiotics was affected most, compared to the cephalosporin-type beta-lactam antibiotics. The M. tuberculosis mutant had no detectable beta-lactamase activity, while the M. smegmatis mutant had a residual type 1 beta-lactamase activity. We identified a gene, blaE, encoding a putative cephalosporinase in M. smegmatis. A double beta-lactamase mutant of M. smegmatis, PM976 (DeltablaS1DeltablaE : : res), had no detectable beta-lactamase activity, but its susceptibility to beta-lactam antibiotics was not significantly different from that of the DeltablaS1 parental strain, PM759. The mutants generated in this study will help determine the contribution of other beta-lactam resistance mechanisms in addition to serving as tools to study the biology of peptidoglycan biosynthesis in these organisms.
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Affiliation(s)
- Anthony R Flores
- University of Rochester School of Medicine and Dentistry and Department of Microbiology and Immunology, Rochester, NY 14642, USA
| | - Linda M Parsons
- The Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Martin S Pavelka
- University of Rochester School of Medicine and Dentistry and Department of Microbiology and Immunology, Rochester, NY 14642, USA
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Flores AR, Parsons LM, Pavelka MS. Characterization of novel Mycobacterium tuberculosis and Mycobacterium smegmatis mutants hypersusceptible to beta-lactam antibiotics. J Bacteriol 2005; 187:1892-900. [PMID: 15743935 PMCID: PMC1064048 DOI: 10.1128/jb.187.6.1892-1900.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Our laboratory previously constructed mutants of Mycobacterium tuberculosis and Mycobacterium smegmatis with deletions in the genes for their major beta-lactamases, BlaC and BlaS, respectively, and showed that the mutants have increased susceptibilities to most beta-lactam antibiotics, particularly the penicillins. However, there is still a basal level of resistance in the mutants to certain penicillins, and the susceptibilities of the mutants to some cephalosporin-based beta-lactams are essentially the same as those of the wild types. We hypothesized that characterizing additional mutants (derived from beta-lactamase deletion mutants) that are hypersusceptible to beta-lactam antibiotics might reveal novel genes involved with other mechanisms of beta-lactam resistance, peptidoglycan assembly, and cell envelope physiology. We report here the isolation and characterization of nine beta-lactam antibiotic-hypersusceptible transposon mutants, two of which have insertions in genes known to be involved with peptidoglycan biosynthesis (ponA2 and dapB); the other seven mutants have insertions which affect novel genes. These genes can be classified into three groups: those involved with peptidoglycan biosynthesis, cell division, and other cell envelope processes. Two of the peptidoglycan-biosynthetic genes (ponA2 and pbpX) may encode beta-lactam antibiotic-resistant enzymes proposed to be involved with the synthesis of the unusual diaminopimelyl linkages within the mycobacterial peptidoglycan.
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Affiliation(s)
- Anthony R Flores
- Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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Consaul SA, Wright LF, Mahapatra S, Crick DC, Pavelka MS. An unusual mutation results in the replacement of diaminopimelate with lanthionine in the peptidoglycan of a mutant strain of Mycobacterium smegmatis. J Bacteriol 2005; 187:1612-20. [PMID: 15716431 PMCID: PMC1064014 DOI: 10.1128/jb.187.5.1612-1620.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterial peptidoglycan contains L-alanyl-D-iso-glutaminyl-meso-diaminopimelyl-D-alanyl-D-alanine peptides, with the exception of the peptidoglycan of Mycobacterium leprae, in which glycine replaces the L-alanyl residue. The third-position amino acid of the peptides is where peptidoglycan cross-linking occurs, either between the meso-diaminopimelate (DAP) moiety of one peptide and the penultimate D-alanine of another peptide or between two DAP residues. We previously described a collection of spontaneous mutants of DAP-auxotrophic strains of Mycobacterium smegmatis that can grow in the absence of DAP. The mutants are grouped into seven classes, depending on how well they grow without DAP and whether they are sensitive to DAP, temperature, or detergent. Furthermore, the mutants are hypersusceptible to beta-lactam antibiotics when grown in the absence of DAP, suggesting that these mutants assemble an abnormal peptidoglycan. In this study, we show that one of these mutants, M. smegmatis strain PM440, utilizes lanthionine, an unusual bacterial metabolite, in place of DAP. We also demonstrate that the abilities of PM440 to grow without DAP and use lanthionine for peptidoglycan biosynthesis result from an unusual mutation in the putative ribosome binding site of the cbs gene, encoding cystathionine beta-synthase, an enzyme that is a part of the cysteine biosynthetic pathway.
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Affiliation(s)
- Sandra A Consaul
- University of Rochester Medical Center, Department of Microbiology and Immunology, 601 Elmwood Ave., Box 672, Rochester, NY 14642, USA
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