Alternative Technologies for In Situ Bioremediation of Radioactive Iodine: Microbial Reductive Methylation of Iodate to Iodocarbon Gas
EMSL Project ID
50930
Abstract
The reductive methylation of water soluble iodate (IO3-) to volatile iodine (iodocarbon) gas forms the basis of alternative remediation technologies in iodine-contaminated subsurface environments. The specific aim of the proposed FY2019 FICUS research project is to determine the transcriptome and proteome of Shewanella oneidensis catalyzing the step-wise reductive methylation of IO3- to the volatile iodocarbon gas methyl iodide (CH3I) with iodide (I-) as reactive intermediate. The molecular mechanism of microbial iodocarbon gas formation under anaerobic conditions is largely unexplored. Identification of the transcriptome and proteome of S. oneidensis during iodocarbon gas formation will thus shed light on the molecular mechanism of microbially catalyzed reductive methylation of iodate under anaerobic conditions. In a collaboration with Pacific Northwest National Laboratory, we recently discovered that S. oneidensis-catalyzed reduction of IO3- under anaerobic conditions requires components of the S. oneidensis metal reduction (Mtr) pathway. Results of chemical and transposon mutagenesis also indicated that IO3- reduction by S. oneidensis involved the formate hydrogenlyase (FHL) complex. Heterologous gene cloning experiments identified an iodide-specific methyl halide transferase (MHT) enzyme that produces volatile iodocarbon compounds such as CH3I. Based on these findings, we postulate that S. oneidensis transforms IO3- to volatile iodocarbons under anaerobic conditions via a two-step, formate-dependent reductive methylation pathway consisting of IO3- reduction to I- (Step 1) followed by I- methylation to CH3I (Step 2). Results of the proposed transcriptomic and proteomic analyses will identify cellular components of the S. oneidensis-catalyzed iodate reductive methylation pathway and will provide information critical to future application of microbial iodine gas formation as an alternative in situ remediation technology in iodine-contaminated subsurface environments.
Project Details
Project type
FICUS Research
Start Date
2019-10-01
End Date
2021-12-31
Status
Closed
Released Data Link
Team
Principal Investigator