DETECTION OF THE MERA GENE AND ITS EXPRESSION IN THE ENVIRONMENT

Bacterial transformation of mercury in the environment has received mu ch attention owing to the toxicity of both the ionic form and organome rcurial compounds, Bacterial resistance to mercury and the role of bac teria in mercury cycling have been widely studied. The genes specifyin g the required functions for resistance to mercury are organized on th e mer operon. Gene probing methodologies have been used for several ye ars to detect specific gene sequences in the environment that are homo logous to cloned mer genes. While mer genes have been detected in a wi de variety of environments, less is known about the expression of thes e genes under environmental conditions. We combined new methodologies for recovering specific gene mRNA transcripts and mercury detection wi th a previously described method for determining biological potential for mercury volatilization to examine the effect of mercury concentrat ions and nutrient availability on rates of mercury volatilization and merA transcription. Levels of merA-specific transcripts and Hg(II) vol atilization were influenced more by microbial activity (as manipulated by nutrient additions) than by the concentration of total mercury. Th e detection of merA-specific transcripts in some samples that did not reduce Hg(II) suggests that rates of-mercury volatilization in the env ironment may not always be proportional to merA transcription.