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Kantnerová K, Kuhlbusch N, Juchelka D, Hilkert A, Kopf S, Neubauer C. A guide to precise measurements of isotope abundance by ESI-Orbitrap MS. Nat Protoc 2024; 19:2435-2466. [PMID: 38654136 DOI: 10.1038/s41596-024-00981-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 02/08/2024] [Indexed: 04/25/2024]
Abstract
Stable isotopes of carbon, hydrogen, nitrogen, oxygen and sulfur are widespread in nature. Nevertheless, their relative abundance is not the same everywhere. This is due to kinetic isotope effects in enzymes and other physical principles such as equilibrium thermodynamics. Variations in isotope ratios offer unique insights into environmental pollution, trophic relationships in ecology, metabolic disorders and Earth history including climate history. Although classical isotope ratio mass spectrometry (IRMS) techniques still struggle to access intramolecular information like site-specific isotope abundance, electrospray ionization-Orbitrap mass spectrometry can be used to achieve precise and accurate intramolecular quantification of isotopically substituted molecules ('isotopocules'). This protocol describes two procedures. In the first one, we provide a step-by-step beginner's guide for performing multi-elemental, intramolecular and site-specific stable isotope analysis in unlabeled polar solutes by direct infusion. Using a widely available calibration solution, isotopocules of trifluoroacetic acid and immonium ions from the model peptide MRFA are quantified. In the second approach, nitrate is used as a simple model for a flow injection routine that enables access to a diverse range of naturally occurring isotopic signatures in inorganic oxyanions. Each procedure takes 2-3 h to complete and requires expertise only in general mass spectrometry. The workflows use optimized Orbitrap IRMS data-extraction and -processing software and are transferable to various analytes amenable to soft ionization, including metabolites, peptides, drugs and environmental pollutants. Optimized mass spectrometry systems will enable intramolecular isotope research in many areas of biology.
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Affiliation(s)
- Kristýna Kantnerová
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, CO, USA
| | - Nils Kuhlbusch
- Thermo Fisher Scientific GmbH, Bremen, Germany
- University of Münster, Münster, Germany
| | | | | | - Sebastian Kopf
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, CO, USA
| | - Cajetan Neubauer
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, CO, USA.
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2
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Gessler A, Wieloch T, Saurer M, Lehmann MM, Werner RA, Kammerer B. The marriage between stable isotope ecology and plant metabolomics - new perspectives for metabolic flux analysis and the interpretation of ecological archives. THE NEW PHYTOLOGIST 2024. [PMID: 39021246 DOI: 10.1111/nph.19973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Accepted: 07/01/2024] [Indexed: 07/20/2024]
Abstract
Even though they share many thematical overlaps, plant metabolomics and stable isotope ecology have been rather separate fields mainly due to different mass spectrometry demands. New high-resolution bioanalytical mass spectrometers are now not only offering high-throughput metabolite identification but are also suitable for compound- and intramolecular position-specific isotope analysis in the natural isotope abundance range. In plant metabolomics, label-free metabolic pathway and metabolic flux analysis might become possible when applying this new technology. This is because changes in the commitment of substrates to particular metabolic pathways and the activation or deactivation of others alter enzyme-specific isotope effects. This leads to differences in intramolecular and compound-specific isotope compositions. In plant isotope ecology, position-specific isotope analysis in plant archives informed by metabolic pathway analysis could be used to reconstruct and separate environmental impacts on complex metabolic processes. A technology-driven linkage between the two disciplines could allow to extract information on environment-metabolism interaction from plant archives such as tree rings but also within ecosystems. This would contribute to a holistic understanding of how plants react to environmental drivers, thus also providing helpful information on the trajectories of the vegetation under the conditions to come.
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Affiliation(s)
- Arthur Gessler
- Institute of Terrestrial Ecosystems, ETH Zurich, 8092, Zurich, Switzerland
- Ecosystem Ecology, Swiss Federal Research Institute WSL, 8903, Birmensdorf, Switzerland
| | - Thomas Wieloch
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
- Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå Plant Science Centre, 90736, Umeå, Sweden
| | - Matthias Saurer
- Ecosystem Ecology, Swiss Federal Research Institute WSL, 8903, Birmensdorf, Switzerland
| | - Marco M Lehmann
- Ecosystem Ecology, Swiss Federal Research Institute WSL, 8903, Birmensdorf, Switzerland
- Forest Soils and Biogeochemistry, Swiss Federal Research Institute WSL, 8903, Birmensdorf, Switzerland
| | - Roland A Werner
- Institute of Agricultural Sciences, ETH Zurich, 8092, Zurich, Switzerland
| | - Bernd Kammerer
- Core Competence Metabolomics, Albert-Ludwigs-University Freiburg, 79104, Freiburg, Germany
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3
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Caro TA, McFarlin J, Jech S, Fierer N, Kopf S. Hydrogen stable isotope probing of lipids demonstrates slow rates of microbial growth in soil. Proc Natl Acad Sci U S A 2023; 120:e2211625120. [PMID: 37036980 PMCID: PMC10120080 DOI: 10.1073/pnas.2211625120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 03/06/2023] [Indexed: 04/12/2023] Open
Abstract
The rate at which microorganisms grow and reproduce is fundamental to our understanding of microbial physiology and ecology. While soil microbiologists routinely quantify soil microbial biomass levels and the growth rates of individual taxa in culture, there is a limited understanding of how quickly microbes actually grow in soil. For this work, we posed the simple question: what are the growth rates of soil microorganisms? In this study, we measure these rates in three distinct soil environments using hydrogen-stable isotope probing of lipids with 2H-enriched water. This technique provides a taxa-agnostic quantification of in situ microbial growth from the degree of 2H enrichment of intact polar lipid compounds ascribed to bacteria and fungi. We find that growth rates in soil are quite slow and correspond to average generation times of 14 to 45 d but are also highly variable at the compound-specific level (4 to 402 d), suggesting differential growth rates among community subsets. We observe that low-biomass microbial communities exhibit more rapid growth rates than high-biomass communities, highlighting that biomass quantity alone does not predict microbial productivity in soil. Furthermore, within a given soil, the rates at which specific lipids are being synthesized do not relate to their quantity, suggesting a general decoupling of microbial abundance and growth in soil microbiomes. More generally, we demonstrate the utility of lipid-stable isotope probing for measuring microbial growth rates in soil and highlight the importance of measuring growth rates to complement more standard analyses of soil microbial communities.
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Affiliation(s)
- Tristan A. Caro
- Department of Geological Sciences, University of Colorado Boulder, Boulder, CO80309
| | - Jamie McFarlin
- Department of Geology and Geophysics, University of Wyoming, Laramie, WY82071
| | - Sierra Jech
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO80309
| | - Noah Fierer
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO80309
- Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO80309
| | - Sebastian Kopf
- Department of Geological Sciences, University of Colorado Boulder, Boulder, CO80309
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4
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Neubauer C, Kantnerová K, Lamothe A, Savarino J, Hilkert A, Juchelka D, Hinrichs KU, Elvert M, Heuer V, Elsner M, Bakkour R, Julien M, Öztoprak M, Schouten S, Hattori S, Dittmar T. Discovering Nature's Fingerprints: Isotope Ratio Analysis on Bioanalytical Mass Spectrometers. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:525-537. [PMID: 36971362 DOI: 10.1021/jasms.2c00363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
For a generation or more, the mass spectrometry that developed at the frontier of molecular biology was worlds apart from isotope ratio mass spectrometry, a label-free approach done on optimized gas-source magnetic sector instruments. Recent studies show that electrospray-ionization Orbitraps and other mass spectrometers widely used in the life sciences can be fine-tuned for high-precision isotope ratio analysis. Since isotope patterns form everywhere in nature based on well-understood principles, intramolecular isotope measurements allow unique insights into a fascinating range of research topics. This Perspective introduces a wider readership to current topics in stable isotope research with the aim of discussing how soft-ionization mass spectrometry coupled with ultrahigh mass resolution can enable long-envisioned progress. We highlight novel prospects of observing isotopes in intact polar compounds and speculate on future directions of this adventure into the overlapping realms of biology, chemistry, and geology.
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Affiliation(s)
- Cajetan Neubauer
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, Colorado 80303, United States
| | - Kristýna Kantnerová
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, Colorado 80303, United States
| | - Alexis Lamothe
- University Grenoble Alpes, CNRS, IRD, INRAE, Grenoble-INP, IGE, Grenoble 38400, France
| | - Joel Savarino
- University Grenoble Alpes, CNRS, IRD, INRAE, Grenoble-INP, IGE, Grenoble 38400, France
| | | | | | - Kai-Uwe Hinrichs
- MARUM Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Marcus Elvert
- MARUM Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Verena Heuer
- MARUM Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Martin Elsner
- Department of Chemistry, Technical University of Munich, D-85748 Garching, Germany
| | - Rani Bakkour
- Department of Chemistry, Technical University of Munich, D-85748 Garching, Germany
| | - Maxime Julien
- GFZ German Research Center for Geosciences, 14473 Potsdam, Germany
| | - Merve Öztoprak
- NIOZ Royal Netherlands Institute for Sea Research, Texel 1797 SZ, Netherlands
| | - Stefan Schouten
- NIOZ Royal Netherlands Institute for Sea Research, Texel 1797 SZ, Netherlands
| | - Shohei Hattori
- International Center for Isotope Effects Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China
| | - Thorsten Dittmar
- Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, 26129 Oldenburg, Germany
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Koch GW, Schwartz E. Isotopic labeling of metabolic water with 18 O 2. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37:e9447. [PMID: 36464810 DOI: 10.1002/rcm.9447] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 11/23/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
RATIONALE Water is the medium of life, is involved in biochemical reactions, and is exchanged among internal pools and with the water in the external environment of organisms. Understanding these processes can be improved by isotopically labeling the metabolic water that is produced inside the cells of organisms during aerobic respiration. METHODS Here we describe a new method for isotopically labeling cellular water by incubating microbes and plant tissues in air enriched in 18 O2 . As oxygen gas is reduced during respiration, H2 18 O is produced. The rate of H2 18 O production and the synthesis of biomolecules that incorporate 18 O from H2 18 O can be quantified using cavity ringdown spectrometry and isotope ratio mass spectrometry. RESULTS For Escherichia coli in solution culture, soil microbial communities, and respiring tissues of plants, the amount of H2 18 O produced was strongly correlated with that of 18 O2 consumed during incubations. Measurements of 18 O in DNA, microbial biomass, and CO2 showed that metabolic water was an important substrate in biosynthesis reactions. CONCLUSIONS Any organism with aerobic respiration is amenable to labeling with 18 O2 , and the method described here enables a new approach to investigate questions regarding plant and microbial physiology. In plants, 18 O introduced as metabolic water could be tracked as it moves between living cells and exchanges with external water. For probing soil microbial physiology, the method described here has the advantage over the application of exogenous H2 18 O of not increasing the soil moisture, a disturbance that can affect microbial metabolism.
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Affiliation(s)
- George W Koch
- Department of Biological Sciences and Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, Arizona, USA
| | - Egbert Schwartz
- Department of Biological Sciences and Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, Arizona, USA
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Kim J, Seo S, Kim TY. Metabolic deuterium oxide (D 2O) labeling in quantitative omics studies: A tutorial review. Anal Chim Acta 2023; 1242:340722. [PMID: 36657897 DOI: 10.1016/j.aca.2022.340722] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 11/25/2022] [Accepted: 12/13/2022] [Indexed: 12/15/2022]
Abstract
Mass spectrometry (MS) is an invaluable tool for sensitive detection and characterization of individual biomolecules in omics studies. MS combined with stable isotope labeling enables the accurate and precise determination of quantitative changes occurring in biological samples. Metabolic isotope labeling, wherein isotopes are introduced into biomolecules through biosynthetic metabolism, is one of the main labeling strategies. Among the precursors employed in metabolic isotope labeling, deuterium oxide (D2O) is cost-effective and easy to implement in any biological systems. This tutorial review aims to explain the basic principle of D2O labeling and its applications in omics research. D2O labeling incorporates D into stable C-H bonds in various biomolecules, including nucleotides, proteins, lipids, and carbohydrates. Typically, D2O labeling is performed at low enrichment of 1%-10% D2O, which causes subtle changes in the isotopic distribution of a biomolecule, instead of the complete separation between labeled and unlabeled samples in a mass spectrum. D2O labeling has been employed in various omics studies to determine the metabolic flux, turnover rate, and relative quantification. Moreover, the advantages and challenges of D2O labeling and its future prospects in quantitative omics are discussed. The economy, versatility, and convenience of D2O labeling will be beneficial for the long-term omics studies for higher organisms.
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Affiliation(s)
- Jonghyun Kim
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea
| | - Seungwoo Seo
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea
| | - Tae-Young Kim
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea.
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7
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Larson EA, Rensner JJ, Larsen KR, Bellaire B, Lee YJ. Rapid Antibiotic Susceptibility Testing by Deuterium Labeling of Bacterial Lipids in On-Target Microdroplet Cultures. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1221-1228. [PMID: 35623100 PMCID: PMC9264383 DOI: 10.1021/jasms.2c00056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Antimicrobial resistance is a serious challenge facing human and veterinary health. Current methods of detecting resistance are limited in turn-around time or universal detection. In this work, a new antimicrobial susceptibility test is developed and validated, which utilizes deuterium labeling of membrane lipids to track the growth of bacterial cells. We hypothesize that deuterium uptake and subsequent labeling of lipids can be detected using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Additionally, bacteria growth is performed on the MALDI target, minimizing sample preparation materials and time. When two Escherichia coli strains are grown in the presence of deuterium oxide, labeling can be detected in as little as 30 min to 2 h. The labeling efficiency, or the ratio of labeled to unlabeled lipid peaks, provides information about the growth rate of bacteria. This growth ratio can differentiate between resistant and susceptible strains of bacteria as a resistant strain will maintain ∼50% labeling efficiency between untreated and treated cultures. In comparison, a susceptible strain will see a decrease in fractional abundance of deuterium from ∼50% in the untreated to ∼10% in the treated. This approach is applied to measure the minimum inhibitory concentration (MIC) of the resistant and susceptible strains from on-target microdroplet culture in a range of antibiotic concentrations. The first antibiotic concentration with a significant decrease in fractional abundance of deuterium correlates well with a traditionally obtained MIC using broth dilution, indicating the clinical relevance of the results.
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Affiliation(s)
- Evan A. Larson
- Department
of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Josiah J. Rensner
- Department
of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Kristina R. Larsen
- Department
of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, Iowa 50011, United States
| | - Bryan Bellaire
- Department
of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, Iowa 50011, United States
| | - Young Jin Lee
- Department
of Chemistry, Iowa State University, Ames, Iowa 50011, United States
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8
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Hilkert A, Böhlke JK, Mroczkowski SJ, Fort KL, Aizikov K, Wang XT, Kopf SH, Neubauer C. Exploring the Potential of Electrospray-Orbitrap for Stable Isotope Analysis Using Nitrate as a Model. Anal Chem 2021; 93:9139-9148. [PMID: 34165950 DOI: 10.1021/acs.analchem.1c00944] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Widely used isotope ratio mass spectrometers have limited capabilities to measure metabolites, drugs, or small polyatomic ions without the loss of structural isotopic information. A new approach has recently been introduced that uses electrospray ionization Orbitrap to measure multidimensional isotope signatures of intact polar compounds. Using nitrate as a model compound, this study aims to establish performance metrics for comparisons with conventional IRMS at the natural abundance level. We present a framework on how to convert isotopolog intensities to δ values that are commonly used in the isotope geochemistry community. The quantification of seven nitrate isotopologs provides multiple pathways for obtaining the primary N and O δ values including non-mass-dependent O isotope variations, as well as opportunities to explore nonrandom isotopic distributions (i.e., clumping effects) within molecular nitrate. Using automation and the adaptation of measurement principles that are specific to isotope ratio analysis, nitrate δ15NAIR, δ18OVSMOW, and δ17OVSMOW were measured with a long-term precision of 0.4‰ or better for isotopic reference materials and purified nitrate from environmental samples. In addition, we demonstrate promising results for unpurified environmental samples in liquid form. With these new developments, this study connects the two largely disparate mass spectrometry fields of bioanalytical MS and isotope ratio MS, thus providing a route to measure new isotopic signatures in diverse organic and inorganic solutes.
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Affiliation(s)
- Andreas Hilkert
- Thermo Fisher Scientific (Bremen), Hanna-Kunath Strasse 11, 28199 Bremen, Germany
| | - John K Böhlke
- U.S. Geological Survey, Reston, Virginia 20192, United States
| | | | - Kyle L Fort
- Thermo Fisher Scientific (Bremen), Hanna-Kunath Strasse 11, 28199 Bremen, Germany
| | - Konstantin Aizikov
- Thermo Fisher Scientific (Bremen), Hanna-Kunath Strasse 11, 28199 Bremen, Germany
| | - Xingchen T Wang
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Sebastian H Kopf
- Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309, United States.,Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80303, United States
| | - Cajetan Neubauer
- Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80303, United States
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9
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Neubauer C, Crémière A, Wang XT, Thiagarajan N, Sessions AL, Adkins JF, Dalleska NF, Turchyn AV, Clegg JA, Moradian A, Sweredoski MJ, Garbis SD, Eiler JM. Stable Isotope Analysis of Intact Oxyanions Using Electrospray Quadrupole-Orbitrap Mass Spectrometry. Anal Chem 2020; 92:3077-3085. [PMID: 32011865 DOI: 10.1021/acs.analchem.9b04486] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The stable isotopes of sulfate, nitrate, and phosphate are frequently used to study geobiological processes of the atmosphere, ocean, as well as land. Conventionally, the isotopes of these and other oxyanions are measured by isotope-ratio sector mass spectrometers after conversion into gases. Such methods are prone to various limitations on sensitivity, sample throughput, or precision. In addition, there is no general tool that can analyze several oxyanions or all the chemical elements they contain. Here, we describe a new approach that can potentially overcome some of these limitations based on electrospray hyphenated with Quadrupole Orbitrap mass spectrometry. This technique yields an average accuracy of 1-2‰ for sulfate δ34S and δ18O and nitrate δ15N and δ18O, based on in-house and international standards. Less abundant variants such as δ17O, δ33S, and δ36S, and the 34S-18O "clumped" sulfate can be quantified simultaneously. The observed precision of isotope ratios is limited by the number of ions counted. The counting of rare ions can be accelerated by removing abundant ions with the quadrupole mass filter. Electrospray mass spectrometry (ESMS) exhibits high-throughput and sufficient sensitivity. For example, less than 1 nmol sulfate is required to determine 18O/34S ratios with 0.2‰ precision within minutes. A purification step is recommended for environmental samples as our proposed technique is susceptible to matrix effects. Building upon these initial provisions, new features of the isotopic anatomy of mineral ions can now be explored with ESMS instruments that are increasingly available to bioanalytical laboratories.
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Affiliation(s)
- Cajetan Neubauer
- Division of Geological and Planetary Sciences , California Institute of Technology , Pasadena , California 91125 , United States
| | - Antoine Crémière
- Division of Geological and Planetary Sciences , California Institute of Technology , Pasadena , California 91125 , United States
| | - Xingchen T Wang
- Division of Geological and Planetary Sciences , California Institute of Technology , Pasadena , California 91125 , United States.,Department of Earth and Environmental Sciences , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Nivedita Thiagarajan
- Division of Geological and Planetary Sciences , California Institute of Technology , Pasadena , California 91125 , United States
| | - Alex L Sessions
- Division of Geological and Planetary Sciences , California Institute of Technology , Pasadena , California 91125 , United States
| | - Jess F Adkins
- Division of Geological and Planetary Sciences , California Institute of Technology , Pasadena , California 91125 , United States
| | - Nathan F Dalleska
- Environmental Analysis Center , California Institute of Technology , Pasadena , California 91125 , United States
| | - Alexandra V Turchyn
- Department of Earth Sciences , University of Cambridge , Cambridge , CB2 3EQ , United Kingdom
| | - Josephine A Clegg
- Department of Earth Sciences , University of Cambridge , Cambridge , CB2 3EQ , United Kingdom
| | - Annie Moradian
- Proteome Exploration Laboratory , California Institute of Technology , Pasadena , California 91125 , United States
| | - Michael J Sweredoski
- Proteome Exploration Laboratory , California Institute of Technology , Pasadena , California 91125 , United States
| | - Spiros D Garbis
- Proteome Exploration Laboratory , California Institute of Technology , Pasadena , California 91125 , United States
| | - John M Eiler
- Division of Geological and Planetary Sciences , California Institute of Technology , Pasadena , California 91125 , United States
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10
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Deuterium and its impact on living organisms. Folia Microbiol (Praha) 2019; 64:673-681. [DOI: 10.1007/s12223-019-00740-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 07/15/2019] [Indexed: 12/12/2022]
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11
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Refining the Application of Microbial Lipids as Tracers of Staphylococcus aureus Growth Rates in Cystic Fibrosis Sputum. J Bacteriol 2018; 200:JB.00365-18. [PMID: 30249710 DOI: 10.1128/jb.00365-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 09/19/2018] [Indexed: 02/04/2023] Open
Abstract
Chronic lung infections in cystic fibrosis (CF) could be treated more effectively if the effects of antimicrobials on pathogens in situ were known. Here, we compared changes in the microbial community composition and pathogen growth rates in longitudinal studies of seven pediatric CF patients undergoing intravenous antibiotic administration during pulmonary exacerbations. The microbial community composition was determined by counting rRNA with NanoString DNA analysis, and growth rates were obtained by incubating CF sputum with heavy water and tracing incorporation of deuterium into two branched-chain ("anteiso") fatty acids (a-C15:0 and a-C17:0) using gas chromatography-mass spectrometry (GC/MS). Prior to this study, both lipids were thought to be specific for Staphylococcaceae; hence, their isotopic enrichment was interpreted as a growth proxy for Staphylococcus aureus Our experiments revealed, however, that Prevotella is also a relevant microbial producer of a-C17:0 fatty acid in some CF patients; thus, deuterium incorporation into these lipids is better interpreted as a more general pathogen growth rate proxy. Even accounting for a small nonmicrobial background source detected in some patient samples, a-C15:0 fatty acid still appears to be a relatively robust proxy for CF pathogens, revealing a median generation time of ∼1.5 days, similar to prior observations. Contrary to our expectation, pathogen growth rates remained relatively stable throughout exacerbation treatment. We suggest two straightforward "best practices" for application of stable-isotope probing to CF sputum metabolites: (i) parallel determination of microbial community composition in CF sputum using culture-independent tools and (ii) assessing background levels of the diagnostic metabolite.IMPORTANCE In chronic lung infections, populations of microbial pathogens change and mature in ways that are often unknown, which makes it challenging to identify appropriate treatment options. A promising tool to better understand the physiology of microorganisms in a patient is stable-isotope probing, which we previously developed to estimate the growth rates of S. aureus in cystic fibrosis (CF) sputum. Here, we tracked microbial communities in a cohort of CF patients and found that anteiso fatty acids can also originate from other sources in CF sputum. This awareness led us to develop a new workflow for the application of stable-isotope probing in this context, improving our ability to estimate pathogen generation times in clinical samples.
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