Fig. 7.

Preexposure of two DSRB cultures to mercury did not increase MeHg production rates. D. desulfuricans ND132 and D. desulfuricans T2 were exposed to 0, 0.5, 5, or 50 μg Hg/ml through four batch culture cycles and then assayed for MeHg production from batch cultures with 500 ng/ml added HgCl₂. Bars show the amount of MeHg produced by cells preexposed to different Hg concentrations. Each bar represents the average and standard deviation of results from 4 methylation assays. Cell growth was not affected by preexposure to Hg, as assessed by the final optical density and the growth rate in the methylation assays (data not shown).