The antagonistic role of selenium in mercury bioassimilation by living organisms

摘要

Our first results showed a clear antagonistic effect between Se and Hg in the tissues of two freshwater fish species, yellow perch and walleye. This was confirmed by the low levels of Hg in tissues containing high concentrations of Se. We present results showing similar trends with other aquatic species situated at lower levels of the food chain in lakes characterized by various levels of dissolved Hg and Se. Higher concentrations of total Hg and methyl mercury in tissues of zooplankton, mayflies and amphipods can be directly correlated with increasing distance from Sudbury smelters and inversely correlated with Se concentrations in lake water, once again suggesting the action of an antagonistic mechanism of Se on Hg assimilation. A separate study on the bacterium Pseudomonas fluorescens shows that bacteria can develop a detoxifying mechanism to eliminate an excess of Se by reducing it to an insoluble form of Se(0) and reducing Hg:' by generating a volatile form of the metal, likely Hg(0) through the onset of some mercury reductase enzymes. When the two elements are present in the culture, it appears clearly that Se is playing a detoxifying role by limiting the availability of Hg to the bacteria.