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 fluorine-induced 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 bacterial headspace above a tellurate-amended culture was achieved by
comparison with the chromatographic retention time of an authentic (CH3)2Te
standard and by gas chromatography/mass spectrometry (see red
adjacent figure).
The time course production of dimethyl telluride varied with amendment salts' Te 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 (see blue adjacent figure). Black elemental Te (Te0) was produced by live cultures amended with Te salts but not by sterile controls. The amount of tellurium in the solid phase (as Te0 and in/or on cells) harvested from replicate, anaerobic cultures of P. fluorescens sampled after 92 hours of incubation was approximately 34%.