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Wood PL, Erol E. Construction of a Bacterial Lipidomics Analytical Platform: Pilot Validation with Bovine Paratuberculosis Serum. Metabolites 2023; 13:809. [PMID: 37512516 PMCID: PMC10383236 DOI: 10.3390/metabo13070809] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 06/23/2023] [Accepted: 06/27/2023] [Indexed: 07/30/2023] Open
Abstract
Lipidomics analyses of bacteria offer the potential to detect and monitor infections in a host since many bacterial lipids are not present in mammals. To evaluate this omics approach, we first built a database of bacterial lipids for representative Gram-positive and Gram-negative bacteria. Our lipidomics analysis of the reference bacteria involved high-resolution mass spectrometry and electrospray ionization with less than a 1.0 ppm mass error. The lipidomics profiles of bacterial cultures clearly distinguished between Gram-positive and Gram-negative bacteria. In the case of bovine paratuberculosis (PTB) serum, we monitored two unique bacterial lipids that we also monitored in Mycobacterium avian subspecies PTB. These were PDIM-B C82, a phthiodiolone dimycocerosate, and the trehalose monomycolate hTMM 28:1, constituents of the bacterial cell envelope in mycolic-containing bacteria. The next step will be to determine if lipidomics can detect subclinical PTB infections which can last 2-to-4 years in bovine PTB. Our data further suggest that it will be worthwhile to continue building our bacterial lipidomics database and investigate the further utility of this approach in other infections of veterinary and human clinical interest.
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Affiliation(s)
- Paul L Wood
- Metabolomics Unit, College of Veterinary Medicine, Lincoln Memorial University, 6965 Cumberland Gap Pkwy, Harrogate, TN 37752, USA
| | - Erdal Erol
- Department of Veterinary Science, Veterinary Diagnostic Laboratory, University of Kentucky, Lexington, KY 40546, USA
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2
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Lipid and Lipoarabinomannan Isolation and Characterization. Methods Mol Biol 2021. [PMID: 34235650 DOI: 10.1007/978-1-0716-1460-0_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The very high content of structurally diverse and biologically active lipids of exotic structures is the hallmark of Mycobacteria. As such the lipid composition is commonly used to characterize mycobacterial strains at the species and type-species levels. The present chapter describes the methods that allow the purification of the most commonly isolated biologically active lipids and those used for analyzing extractable lipids and their constituents, cell wall-linked mycolic acids (MA), and lipoarabinomannan (LAM). These involve various chromatographic techniques and analytical procedures necessary for structural and metabolic studies of mycobacterial lipids. In addition, as the use of physical methods has brought important overhang on chemical structures of the very-long-chain MA, which typify mycobacteria, NMR and mass spectrometry data of these specific fatty acids are included.
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Alhuwaymil ZS, Al-Araj IQM, Al Dulayymi AR, Jones A, Gates PJ, Valero-Guillén PL, Baird MS, Al Dulayymi JR. Mycobacterium alvei (ω-1)-methoxy mycolic acids: Absolute stereochemistry and synthesis. Chem Phys Lipids 2020; 233:104977. [PMID: 32961166 DOI: 10.1016/j.chemphyslip.2020.104977] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/24/2020] [Accepted: 09/14/2020] [Indexed: 11/28/2022]
Abstract
Cells of Mycobacterium alvei are known to contain a unique set of mycolic acids with a (ω-1)-methoxy group; although the various enzymes in the biosynthesis of other types of mycolic acid have been widely studied, the biosynthetic route to this substituent is unclear. We now define the stereochemistry of the (ω-1)-methoxy fragment as R, and describe the synthesis of a major R-(ω-1)-methoxy-mycolic acid and its sugar esters, and of two natural M. alvei diene mycolic acids.
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Affiliation(s)
- Zamzam S Alhuwaymil
- School of Natural Sciences, Bangor University, Bangor, Gwynedd, LL57 2UW, UK
| | | | - Ahmad R Al Dulayymi
- School of Natural Sciences, Bangor University, Bangor, Gwynedd, LL57 2UW, UK
| | - Alison Jones
- School of Natural Sciences, Bangor University, Bangor, Gwynedd, LL57 2UW, UK
| | - Paul J Gates
- School of Chemistry, Bristol University, Bristol, BS8 1TS, UK
| | - Pedro L Valero-Guillén
- Departamento de Genética y Microbiología, Facultad de Medicina, Universidad de Murcia, Spain, Instituto Murciano de Investigación Biosanitaria (IMIB), Spain
| | - Mark S Baird
- School of Chemistry, Bangor University, Bangor, Gwynedd, LL57 2UW, UK
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Wang HYJ, Tatituri RVV, Goldner NK, Dantas G, Hsu FF. Unveiling the biodiversity of lipid species in Corynebacteria- characterization of the uncommon lipid families in C. glutamicum and pathogen C. striatum by mass spectrometry. Biochimie 2020; 178:158-169. [PMID: 32659445 DOI: 10.1016/j.biochi.2020.07.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/21/2020] [Accepted: 07/03/2020] [Indexed: 10/23/2022]
Abstract
Uncommon lipids in biotechnologically important Corynebacterium glutamicum and pathogen Corynebacterium striatum in genus Corynebacterium are isolated and identified by linear ion-trap multiple stage mass spectrometry (LIT MSn) with high resolution mass measurement. We redefined several lipid structures that were previously mis-assigned or not defined, including cytidine diphosphate diacylglycerol (CDP-DAG), glucuronosyl diacylglycerol (GlcA-DAG), (α-d-mannopyranosyl)-(1 → 4)-(α-D-glucuronyl diacyglycerol (Man-GlcA-DAG), 1-mycolyl-2-acyl-phosphatidylglycerol (MA-PG), acyl trehalose monomycolate (acyl-TMM). We also report the structures of mycolic acid, phosphatidylglycerol, phosphatidylinositol, cardiolipin, trehalose dimycolate lipids in which many isomeric structures are present. The LIT MSn approaches afford identification of the functional group, the fatty acid substituents and their regiospecificity in the molecules, revealing the biodiversities of the lipid species in two Corynebacterium strains that have played very different and important roles in human nutrition and health.
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Affiliation(s)
- Hay-Yan J Wang
- Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biological Sciences, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan
| | - Raju V V Tatituri
- Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital, Harvard Medical School, 60 Fenwood Road, Boston, MA, 02115, USA
| | - Nicholas K Goldner
- The Edison Family Center for Genome Sciences, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Gautam Dantas
- The Edison Family Center for Genome Sciences, Washington University School of Medicine, St Louis, MO 63110, USA; Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO 63110, USA; Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, 63110, USA; Department of Biomedical Engineering, Washington University in St Louis, St Louis, MO 63130, USA
| | - Fong-Fu Hsu
- Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Frankfater C, Henson WR, Juenger-Leif A, Foston M, Moon TS, Turk J, Kao JLF, Haas A, Hsu FF. Structural Determination of a New Peptidolipid Family from Rhodococcus opacus and the Pathogen Rhodococcus equi by Multiple Stage Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:611-623. [PMID: 31967470 DOI: 10.1021/jasms.9b00059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The cell walls of the genus Rhodococcus including the pathogenic bacterium Rhodococcus equi (R. equi) and biotechnologically important bacterium Rhodococcus opacus (R. opacus) contain an abundant peptidolipid (or termed lipopeptide) family whose structures have not been reported previously. Here, we describe a linear ion-trap multiple-stage mass spectrometric (LIT MSn) approach with high resolution mass spectrometry (HRMS), in conjunction with NMR spectroscopy, chemical reactions, and GC/MS analysis to define the structures of these compounds. We employed LIT MSn (n = 2-8) on the [M + Na]+ ion species to establish the peptide sequence, the identity of the fatty acyl substituent, and its location within the molecule, while NMR spectroscopy and GC/MS were used to recognize the Leu and Ile moieties. The major new lipopeptide found in R. opacus is defined as C17H35CH(OH)CH2CO-NHLeu-Ser-Leu-Ile-Thr-Ile-PheCOOH, where a β-OH fatty acyl (C18-C22) substituent is attached to the N-terminal of the LSLITIF peptide chain via a NH-CO bond. By contrast, the main peptidolipids found in R. equi belong to the cyclopeptidolipid family, which possesses the same peptide sequence and lipid chain, but the β-OH group of the fatty acyl moiety and the C-terminus of the peptide (i.e., the -COOH) are cyclized by an ester bond formation to a lactone, with a structure similar to iturin-A (Peypoux, F. et al. Biochemistry 1978, 17, 3992-3996). The antibiotic activity test of these new lipids did not reveal an activity against any of seven microorganisms tested.
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Affiliation(s)
| | | | - Alexandra Juenger-Leif
- Institute for Cell Biology, University of Bonn, Ulrich-Haberland-Strasse 61a, 53121 Bonn, Germany
| | | | | | | | | | - Albert Haas
- Institute for Cell Biology, University of Bonn, Ulrich-Haberland-Strasse 61a, 53121 Bonn, Germany
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Cai T, Guo ZQ, Xu XY, Wu ZJ. Recent (2000-2015) developments in the analysis of minor unknown natural products based on characteristic fragment information using LC-MS. MASS SPECTROMETRY REVIEWS 2018; 37:202-216. [PMID: 27341181 DOI: 10.1002/mas.21514] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 06/02/2016] [Indexed: 06/06/2023]
Abstract
Liquid chromatography-Mass Spectrometry (LC-MS) has been widely used in natural product analysis. Global detection and identification of nontargeted components are desirable in natural product research, for example, in quality control of Chinese herbal medicine. Nontargeted components analysis continues to expand to exciting life science application domains such as metabonomics. With this background, the present review summarizes recent developments in the analysis of minor unknown natural products using LC-MS and mainly focuses on the determination of the molecular formulae, selection of precursor ions, and characteristic fragmentation patterns of the known compounds. This review consists of three parts. Firstly, the methods used to determine unique molecular formula of unknown compounds such as accurate mass measurements, MSn spectra, or relative isotopic abundance information, are introduced. Secondly, the methods improving signal-to-noise ratio of MS/MS spectra by manual-MS/MS or workflow targeting-only signals were elucidated; pure precursor ions can be selected by changing the precursor ion isolated window. Lastly, characteristic fragmentation patterns such as Retro-Diels-Alder (RDA), McLafferty rearrangements, "internal residue loss," and so on, occurring in the molecular ions of natural products are summarized. Classical application of characteristic fragmentation patterns in identifying unknown compounds in extracts and relevant fragmentation mechanisms are presented (RDA reactions occurring readily in the molecular ions of flavanones or isoflavanones, McLafferty-type fragmentation reactions of some natural products such as epipolythiodioxopiperazines; fragmentation by "internal residue loss" possibly involving ion-neutral complex intermediates). © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:202-216, 2018.
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Affiliation(s)
- Tian Cai
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
- Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Ze-Qin Guo
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
- College of Bioengineering, Chongqing University, Chongqing, 400044, China
| | - Xiao-Ying Xu
- Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Zhi-Jun Wu
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
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7
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Crick PJ, Guan XL. Lipid metabolism in mycobacteria--Insights using mass spectrometry-based lipidomics. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1861:60-67. [PMID: 26515252 DOI: 10.1016/j.bbalip.2015.10.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 10/14/2015] [Accepted: 10/23/2015] [Indexed: 11/18/2022]
Abstract
Diseases including tuberculosis and leprosy are caused by species of the Mycobacterium genus and are a huge burden on global health, aggravated by the emergence of drug resistant strains. Mycobacteria have a high lipid content and complex lipid profile including several unique classes of lipid. Recent years have seen a growth in research focused on lipid structures, metabolism and biological functions driven by advances in mass spectrometry techniques and instrumentation, particularly the use of electrospray ionization. Here we review the contributions of lipidomics towards the advancement of our knowledge of lipid metabolism in mycobacterial species.
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Affiliation(s)
- Peter J Crick
- Swiss Tropical and Public Health Institute, CH-4051 Basel, Switzerland; University of Basel, CH-4000 Basel, Switzerland
| | - Xue Li Guan
- Swiss Tropical and Public Health Institute, CH-4051 Basel, Switzerland; University of Basel, CH-4000 Basel, Switzerland; Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore.
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Taher SG, Muzael M, Al Dulayymi JR, Baird MS. Synthetic trehalose esters of cis-alkene and diene α′-mycolic acids of Mycobacteria. Chem Phys Lipids 2015; 189:28-38. [DOI: 10.1016/j.chemphyslip.2015.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 05/18/2015] [Indexed: 11/24/2022]
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Wang C, Wang M, Han X. Applications of mass spectrometry for cellular lipid analysis. MOLECULAR BIOSYSTEMS 2015; 11:698-713. [PMID: 25598407 PMCID: PMC4376555 DOI: 10.1039/c4mb00586d] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Mass spectrometric analysis of cellular lipids is an enabling technology for lipidomics, which is a rapidly-developing research field. In this review, we briefly discuss the principles, advantages, and possible limitations of electrospray ionization (ESI) and matrix assisted laser desorption/ionization (MALDI) mass spectrometry-based methodologies for the analysis of lipid species. The applications of these methodologies to lipidomic research are also summarized.
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Affiliation(s)
- Chunyan Wang
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, 6400 Sanger Road, Orlando, Florida 32827, USA.
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10
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Abstract
Mycobacteria are microorganisms that contain a very high content of structurally diverse lipids, some of them being biologically active substances. As such the lipid composition is commonly used to characterize mycobacterial strains at the species and type-species level. This chapter describes the methods that allow the purification of the most commonly isolated biologically active lipids and those used for analyzing extractable lipids and their constituents, cell wall-linked mycolic acids and lipoarabinomannan (LAM). The latter involve simple chromatographic and analytical techniques, such as thin-layer chromatography and gas chromatography coupled to mass spectrometry.
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Affiliation(s)
- Marie-Antoinette Lanéelle
- Tuberculosis & Infection Biology Department, Institut de Pharmacologie et de BiologieStructurale (IPBS), Centre National de la Recherche Scientifique (CNRS), BP 64182, 205 route de Narbonne, 31077, Toulouse, France
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11
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Whittingham JL, Blagova EV, Finn CE, Luo H, Miranda-CasoLuengo R, Turkenburg JP, Leech AP, Walton PH, Murzin AG, Meijer WG, Wilkinson AJ. Structure of the virulence-associated protein VapD from the intracellular pathogen Rhodococcus equi. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:2139-51. [PMID: 25084333 PMCID: PMC4118825 DOI: 10.1107/s1399004714012632] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 05/30/2014] [Indexed: 01/17/2023]
Abstract
Rhodococcus equi is a multi-host pathogen that infects a range of animals as well as immune-compromised humans. Equine and porcine isolates harbour a virulence plasmid encoding a homologous family of virulence-associated proteins associated with the capacity of R. equi to divert the normal processes of endosomal maturation, enabling bacterial survival and proliferation in alveolar macrophages. To provide a basis for probing the function of the Vap proteins in virulence, the crystal structure of VapD was determined. VapD is a monomer as determined by multi-angle laser light scattering. The structure reveals an elliptical, compact eight-stranded β-barrel with a novel strand topology and pseudo-twofold symmetry, suggesting evolution from an ancestral dimer. Surface-associated octyl-β-D-glucoside molecules may provide clues to function. Circular-dichroism spectroscopic analysis suggests that the β-barrel structure is preceded by a natively disordered region at the N-terminus. Sequence comparisons indicate that the core folds of the other plasmid-encoded virulence-associated proteins from R. equi strains are similar to that of VapD. It is further shown that sequences encoding putative R. equi Vap-like proteins occur in diverse bacterial species. Finally, the functional implications of the structure are discussed in the light of the unique structural features of VapD and its partial structural similarity to other β-barrel proteins.
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Affiliation(s)
- Jean L. Whittingham
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Elena V. Blagova
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Ciaran E. Finn
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Haixia Luo
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Raúl Miranda-CasoLuengo
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Johan P. Turkenburg
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Andrew P. Leech
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Paul H. Walton
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
| | - Alexey G. Murzin
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, England
| | - Wim G. Meijer
- UCD School of Biomolecular and Biomedical Science and UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Anthony J. Wilkinson
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, England
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Prescottia equi gen. nov., comb. nov.: a new home for an old pathogen. Antonie van Leeuwenhoek 2012; 103:655-71. [DOI: 10.1007/s10482-012-9850-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 11/04/2012] [Indexed: 11/26/2022]
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Sydor T, von Bargen K, Hsu FF, Huth G, Holst O, Wohlmann J, Becken U, Dykstra T, Söhl K, Lindner B, Prescott JF, Schaible UE, Utermöhlen O, Haas A. Diversion of phagosome trafficking by pathogenic Rhodococcus equi depends on mycolic acid chain length. Cell Microbiol 2012; 15:458-73. [PMID: 23078612 PMCID: PMC3864644 DOI: 10.1111/cmi.12050] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 09/19/2012] [Accepted: 10/11/2012] [Indexed: 12/30/2022]
Abstract
Rhodococcus equi is a close relative of Mycobacterium spp. and a facultative intracellular pathogen which arrests phagosome maturation in macrophages before the late endocytic stage. We have screened a transposon mutant library of R. equi for mutants with decreased capability to prevent phagolysosome formation. This screen yielded a mutant in the gene for β-ketoacyl-(acyl carrier protein)-synthase A (KasA), a key enzyme of the long-chain mycolic acid synthesizing FAS-II system. The longest kasA mutant mycolic acid chains were 10 carbon units shorter than those of wild-type bacteria. Coating of non-pathogenic E. coli with purified wild-type trehalose dimycolate reduced phagolysosome formation substantially which was not the case with shorter kasA mutant-derived trehalose dimycolate. The mutant was moderately attenuated in macrophages and in a mouse infection model, but was fully cytotoxic.Whereas loss of KasA is lethal in mycobacteria, R. equi kasA mutant multiplication in broth was normal proving that long-chain mycolic acid compounds are not necessarily required for cellular integrity and viability of the bacteria that typically produce them. This study demonstrates a central role of mycolic acid chain length in diversion of trafficking by R. equi.
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Affiliation(s)
- Tobias Sydor
- Institute for Cell Biology, University of Bonn, Bonn, Germany
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Hsu FF, Pacheco S, Turk J, Purdy G. Structural determination of glycopeptidolipids of Mycobacterium smegmatis by high-resolution multiple-stage linear ion-trap mass spectrometry with electrospray ionization. JOURNAL OF MASS SPECTROMETRY : JMS 2012; 47:1269-1281. [PMID: 23019158 PMCID: PMC3462375 DOI: 10.1002/jms.3070] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Glycopeptidolipids (GPLs) are abundant in the cell walls of different species of mycobacteria and consist of tripeptide-amino-alcohol core of D-Phe-D-allo-Thr-D-Ala-L-alaninol linked to 3-hydroxy or 3-methoxy C(26-34) fatty acyl chain at the N-terminal of D-Phe via amide linkage, and a 6-deoxytalose (6-dTal) and an O-methyl rhamnose residues, respectively, attach to D-allo-Thr and the terminal L-alaninol. They are important cell-surface antigens that are implicated in the pathogenesis of opportunistic mycobacteria belonging to the Mycobacterium avium complex. In this contribution, we described multiple-stage linear ion trap in conjunction with high-resolution mass spectrometry towards structural characterization of complex GPLs as [M + Na](+) ions isolated from Mycobacterium smegmatis, a fast-growing and non-pathogenic mycobacterial species. Following resonance excitation in an ion trap, MS(n) spectra of the [M + Na](+) ions of GPLs contained mainly b and y series ions that readily determine the peptide sequence. Fragment ions from MS(n) also afford locating the 6-dTal and O-methyl rhamnose residues linked to the D-allo-Thr and terminal L-alaninol of the peptide core, respectively, as well as recognizing the modifications of the glycosides, including their acetylation and methylation states and the presence of succinyl group. The GPL families consisting of 3-hydroxy fatty acyl and of 3-methoxy fatty acyl substituents are readily distinguishable. The MS profiles of the GPLs from cells are dependant on the conditions they were grown, and several isobaric isomers were identified for many of the molecular species. These multiple-stage mass spectrometric approaches give detailed structures of GPL in complex mixtures of which the isomeric structures are difficult to define using other analytical methods.
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Affiliation(s)
- Fong-Fu Hsu
- Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
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