ABSTRACT
Volatilization through methylation is thought to be a protective mechanism used by microorganisms to avoid Se toxicity in seleniferous environments. In effect, the process permanently removes Se from soil and water under aerobic conditions. The predominant groups of Se-methylating organisms isolated from soils and sediments are bacteria and fungi [22-26]. In water bodies, bacteria are thought to play a dominant role (Table 1) [27]. Biomethylation of toxic Se species, including Se032-, Se042-, Se0, and various organoselenium compounds, into a less toxic, volatile form, DMSe, is apparently a widespread transformation in seleniferous environments [25,28,29]. Dimethylselenide is the major metabolite of Se volatilization, although other Se compounds such as DMDSe, dimethyl selenone ([CH3]2Se02), methane selenol (CH3SeH), and dimethyl selenenyl sulfide (CH3SeSCH3) may also be produced [28,30-32].
