Calculating The Total Biological Production Of Volatile Sulfur And Selenium Compounds By Determining Their Henry's Law Constants

Hakan Gurleyuk and Thomas G. Chasteen

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

Experiments will be described in which gas and solution phase amounts of two organosulfur and two organoselenium compounds were quantitated in bacterial cultures which bioremediate oxyanions of selenium. Although headspace analysis with gas chromatography is a powerful tool for quantitating the volatile compounds produced by a culture, it can not go further than an estimation since some of these compounds remain dissolved in the aqueous medium. Therefore, we determined their Henry's Law constants in the studied bacterial medium at the growth temperature of a phototrophic bacterium, Rhodobacter sphaeroides 2.4.1 and used the ratio of gas phase to solution phase concentrations to determine the total extracellular amounts of these compounds produced by the reduction and methylation of selenate and selenite by this microbe.