FIG. 3.

Effects of thiol modification and temperature on the synthesis of βHgS and Hg(0). (A) Extracellular thiol alkylation by iodoacetamide in Limnothrix planctonica was followed by a 120-ppb Hg(II) application (closed symbols). Controls without alkylation are represented by open symbols. Results for total Hg (squares) and acid reduction-detectable Hg (circles) are shown. (B) Intracellular thiol oxidation by dimethylfumarate in Phormidium limnetica. Cultures were exposed to 140 ppb Hg(II). At 1.5 h (↓), half were treated with dimethylfumarate (triangles); untreated controls are represented by squares. An additional 140 ppb Hg(II) was applied at 1.75 h. Results for total Hg (closed symbols) and acid reduction-detectable Hg (open symbols) are shown. (C) Effect of temperature on biotransformation by Limnothrix planctonica. Mercury-free preincubation was for 150 min, followed by 5-h treatments in 120 ppb Hg(II). Results for acid-detectable Hg (white), total Hg (gray), and β-HgS (black) are shown. All cultures had initial OD₆₆₅s of 0.32. All values are means ± SE for triplicate determinations.