Transcript Identification of dimethyl tellurenyl sulfide and methanetellurol in the headspace gases above tellurium-amended bacterial cultures using gas chromatography with fluorine-induced chemiluminescence and mass spectrometric.

Identification of dimethyl tellurenyl sulfide and methanetellurol
in the headspace gases above tellurium-amended bacterial
cultures using gas chromatography with fluorine-induced
chemiluminescence and
mass spectrometric detection
Presented By: Jerry W. Swearingen Jr.
Mary F. Plishker
Thomas G. Chasteen
Sam Houston State University
Huntsville, TX
Manuel A. Araya
Claudia P. Saavedra
Claudio C. Vásquez
Universidad de Santiago de Chile
Organo-metalloid detection in headspace gases above bacteria
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Methods of Extraction
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Manual Gas Syringe (1mL)
Solid Phase Micro Extraction (SPME)
Instrumentation
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Gas Chromatography – F2-induced
Chemiluminescence Detection
Gas Chromatography – Mass
Spectrometry
Geobacillus stearothermophilus V
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Resistant to TeO3-2 and TeO4-2
Growth Conditions of this thermophile
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Temperature: 60º C
Aerobic Environment
Difficult to perform headspace analysis.
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Oxidation of organo-sulfides and tellurides.
Volatiles are purged out of the headspace.
Genetic Modification of E. Coli JM109 Cells
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Open Reading Frames (ORF)
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ORF 600 – UbiE methyltransferase
ORF 780 – uroporphyrin-III C-methyltransferase (cobA)
ORF 399 – BtuR protein
pSP72 cloning vector
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Plasmid is coded for ampicillin resistance.
DNA was inserted at the HindIII restriction site.
GC- SCD Chromatogram of E. Coli 1VH Headspace
Methanetellurol
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Was the chromatographic peak dimethyl selenide or
methanetellurol?
If so, that means the tellurium amendments were
contaminated with selenium.
Boiling Point of CH3SeCH3 - 54º C
Boiling Point of CH3TeH – 57º C
Gas Phase Concentrations
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Temperature: 37º C
Headspace Pressure: ~1 atm
CH3SSCH3 – 1216 ppbv
CH3TeCH3 – 94 ppbv
CH3TeH and CH3SSSCH3 standards were not available.
GC- MS Total Ion Chromatogram of E. Coli 1VH Headspace
Mass Spectrum of dimethyl tellurenyl sulfide CH3TeTeCH3
Mass Spectrum of dimethyl tellurenyl sulfide - CH3TeSCH3
Synthesis of CH3TeH and CH3TeSCH3
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There are no commercially available standards of CH3TeH and CH3TeSCH3.
A CAS registry number has not been assigned for CH3TeSCH3.
Reaction Mixture
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25 μL CH3SSCH3
25 μL CH3TeTeCH3
1 mL of Reducing Agent
Reducing Agents Used
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1.0 M HCl + zinc
1.0 M H2SO4 + zinc
0.5 mM DL-dithiothreitol (DTT)
GC-SCD Chromatogram of Headspace Above an Aqueous Reaction
Boiling Point Determination
Are DMDS, DMDTe, and DMTeS produced from bacterial metabolism?
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Disproportionation Reaction
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CH3TeSCH3 + CH3SH
CH3TeSCH3 + CH3TeH
Exchange Reaction
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CH3SSCH3 + CH3TeH
CH3TeTeCH3 + CH3SH
CH3SSCH3 + CH3TeTeCH3
2 CH3TeSCH3
Combination Reaction
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2 CH3SH
CH3SSCH3
CH3SH + CH3TeH
CH3TeSCH3
2 CH3TeH
CH3TeTeCH3
The Future – dimethyl tellurenyl selenide – CH3TeSeCH3
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Pseudomonas fluorescens K27
Amend bacterium with any combination of:
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SeO3-2, SeO4-2
TeO3-2, TeO4-2
Synergistic Toxic Effect
B.P. of CH3TeSeCH3 is 173º C (based on chromatography).
The retention time of this compound is 12.78 minutes.
The retention time of CH3SSSCH3 is 12.57 minutes. (170º C)
Adjust the temperature ramp to allow for base line
separation.
Mass Spectrum of dimethyl tellurenyl selenide
Acknowledgements
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This research was supported by the Robert A. Welch
Foundation
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And by FONDECYT (Chile)
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And by DICYT grants from University of Santiago, Chile
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And by a doctoral fellowship from MECESUP (Chile)