SGER: The Rapid Evolution of MerA Encoded Metal Ion Reduction: A Novel Mutagenesis Protocol

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9415295 Meagher Heavy metal contamination has reached toxic levels in many parts of the world and has become an urgent problem. It would be useful to be able to manipulate single gene traits in plants, which could process heavy metals and remediate heavy metal pollution by resistance, sequestration and perhaps even assist in the removal of these contaminants from the environment. The product of the bacterial merA gene, mercuric ion reductase (MerA) can detoxify ionic mercury by reducing it to its less toxic metallic form, Hgo. A highly mutagenized merA gene confers significant levels of resistance to Hg++ in transgenic higher plants. It is hypothesized that MerA can be mutated to direct the efficient reduction of a wide variety of metal ions for harvest or remediation. The specific aims of this research are #1: to explore the present substrate range of MerA; #2: to develop genetic selections or powerful screens for the reduction of gold Au+++, silver (Ag+), lead (Pb++), and cadmium (Cd++) in bacteria; #3: to generate merA mutants with novel substrate specificities (e.g. enhanced reduction of Au+++ and novel reduction of Pb++ and Cd++; and #4: to develop a powerful new RE-PCR (recombination polymerase chain reaction) mutagenesis protocol in which tens of thousands of mutant clones are the only survivors. The method takes advantage of the incredible natural transformability and high frequency of homologous recombination with in certain strains of the soil bacterium, Acinetobacter calcoaceticus. %%% Once developed, this powerful approach will benefit many areas of biological research and development, but in particular, it should accelerate progress in bioremediation. ***