Microbial Transformations and Genetics
The objective of this research is to identify genes involved in SRB and IRB mercury methylation and establish the relationships among environmental conditions and expression of genes involved in mercury methylation. Previous investments by DOE offer a unique opportunity to achieve a molecular-level understanding of mercury methylation by sulfur reducing bacteria that was not previously available. The genetic sequences of two Desulfovibrio that are capable of carrying out the methylation reaction have been obtained and the sequencing of a third is pending at Joint Genome Institute. Comparisons of these sequences with related Desulfovibrio that do not methylate have allowed identification of candidate genes that could be the critical genes involved. Gene expression studies and molecular studies (e.g., knockout studies) will help confirm the identity of the critical proteins. These results will be used to develop a new functional gene arrays to assess the microbial communities in the field and will aid in selection of proteins to be characterized in Biomolecular Structure, Dynamics, and Simulation studies. This Task will also examine biogeochemical influences on Hg methylation and gene expression, which will be used with data from the microcosm and laboratory studies to identify bioavailable Hg species.