Confirmation of the Biomethylation of Antimony Compounds

Hakan Gürleyük, Verena Van Fleet-Stalder, and Thomas. G. Chasteen*

Department of Chemistry, Sam Houston State University, Huntsville, Texas, 77341-2117

Applied Organometallic Chemistry, 1997, 11, 471-483.


Abstract

We have evidence that an organic and an inorganic salt of antimony were reduced and methylated biologically by microorganisms in laboratory experiments. The organoantimony compound produced was trimethylstibine (CH3)3Sb and was detected in culture headspace. This was confirmed by matching the compound's retention time in capillary gas chromatography, as detected by fluorine-induced chemiluminescence, with a commercial standard and by its mass spectrum determined with gas chromatography/mass spectrometry. Trimethylstibine was detected in the headspace of soil samples amended with either potassium antimonyl tartrate or potassium hexahydroxy antimonate and augmented with any one of three different nitrate containing growth media. The identity of the microorganisms in soil that accomplished this are as yet unknown. Of 48 soil samples amended with these two compounds, 24 produced trimethylstibine. Bioreduction of trimethyldibromoantimony was also detected in a liquid monoculture of Pseudomonas fluorescens K27 which also produced trimethylstibine. This headspace production of (CH3)3Sb was determined to be linked to the culture's cell population as measured by optical density. This microbe, however, did not biomethylate either potassium antimonyl tartrate or potassium hexahydroxy antimonate in any experiments we performed.


As the abstract above notes, a strain of Pseudomonas fluorescens isolated by Dr. Ray Fall at the University of Colorado, produces trimethylstibine in the headspace above bacterial cultures grown on minimal medium amended with an antimony compound, trimethyldibromoantimony. The organism is grown anaerobically with nitrate as its terminal electron acceptor in sealed culture tubes with septa (caps) for gas phase sampling using a gas syringe.

The chromatographic determination of trimethylstibine over time (a time course experiment) is seen here, with the headspace concentration of (CH3)3Sb versus time plotted along with the bacterial cell population in replicate tubes of live bacterial cultures. The concentration of trimethyldibromoantimony added to these replicate culture tubes was 0.01 millimolar.

The calibration curve for trimethylstibine-also called trimethyl antimony-generated by our capillary gas chromatograph coupled to a fluorine-induced chemiluminescence detector can be seen here.

Trimethylstibine detection by this instrument broadens the suite of organometalloidal compounds detectable via this chemiluminescence detector. Initially applied to

this systems has also been used for gas phase detection of Earlier work also determined the viability of this system to determine
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