Production of dimethyl telluride and elemental tellurium by bacteria amended with tellurite or tellurate

Abstract

The purpose of this study was to determine whether a facultative anaerobe, Pseudomonas fluorescens K27, would produce dimethyl telluride when anaerobic cultures were amended with differing concentrations of sodium tellurate and/or sodium tellurite and how that volatile organotellurium production varied over time. Batch bacterial bioreactor experiments were undertaken in order to observe the changes in the headspace of a growth medium solution inoculated with P. fluorescens and amended with tellurium salts. Gas samples were taken from the bioreactor every hour and were analyzed by capillary gas chromatography using fluorineinduced chemiluminescence detection to determine compounds in the headspace. Liquid samples were analyzed by spectrophotometer to determine optical densities, which were used as an indicator of cell growth. Verification of the identity of the dimethyl telluride produced in the bacterial headspace above a tellurate-amended culture was achieved by comparison with the chromatographic retention time of an authentic (CH 3 ) 2 Te standard and by gas chromatography/ mass spectrometry. The time course production of dimethyl telluride varied with amendment salts' tellurium oxidation states and concentrations. Increasing tellurate concentrations caused slower bacterial growth, but those cultures reached the stationary phase sooner than cultures amended with tellurite concentrations 10 or 100 times less. Black elemental tellurium

Aeration Controls the Reduction and Methylation of Tellurium by the Aerobic, Tellurite-Resistant Marine Yeast Rhodotorula mucilaginosa

“…Resistance to tellurite has been reported in a few Gram-positive bacteria (2,26,33) and in a number of Gram-negative Proteobacteria (1,7,10,13,22,27,38). To date, all tellurite-resistant microbes reduce tellurite to Te(0) (26,34), and some have been documented to produce volatile, methylated Te species (5,33). Reduction and methylation is thought to be a protective mechanism used by microorganisms to detoxify Te oxyanions.…”

Capillary electrophoretic determination of selenocyanate and selenium and tellurium oxyanions in bacterial cultures

“…The analytical methods previously used for this task were hydride generation atomic absorption spectrometry or ICP. Both techniques are much more involved and substantially slower that the CE method described here, but with comparable detection limits and linear range for ICP but much narrower linear range for AAS, 0 ppb to 20 ppb (Basnayake et al, 2001). …”

“…To investigate bacterial cultures as a means of probing bacteria as a possible source of this anion, this method can be successfully used. Bioremediation of both Se and Te (Araya et al, 2002, Swearingen et al, 2006 was a main point of interest in Dr. Chasteen's research group; however, effort has also been made in this research group to track oxyanion concentrations in growing cultures and the amounts of elemental metalloids produced by metalloid-resistant bacteria as they detoxify their cultures (Hapuarachchi et al, 2004, Basnayake et al, 2001). The analytical methods previously used for this task were hydride generation atomic absorption spectrometry or ICP.…”

“…It can be clearly observed that the peak area of tellurite drops down as the bacterium approaches its death phase. In the first hour after inoculation ~5% of added tellurite has been biologically reduced; Te 0 is eventually seen as a black precipitate (Basnayake et al, 2001), and although this culture reaches stationary phase in 5.5 h, it is only between the 5th and 8th…”

“…Volatile organo-selenium/tellurium compounds such as dimethyl selenide (DMSe), dimethyl diselenide (DMDSe), dimethyl telluride (DMTe), and dimethyl ditelluride (DMDTe) can be determined using gas chromatography (GC) equipped with a fluorine-induced chemiluminescence detector Basnayake et al, 2001). For the identification of unknown compounds, a GC equipped with a mass spectrometer (GC-MS) can be used provided that the concentration of volatiles in the headspace is very high.…”