Reduction of Hypoiodous Acid by Shewanella oneidensis MR-1 Using Extracellular Electron Transfer Components

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Hypoiodous acid (HIO) is a critical iodine species in global biogeochemical cycles.
• Microbial roles in HIO transformation are not well understood.
• Understanding these microbial pathways is essential for iodine cycling research.

Purpose of the Study:

• To investigate the microbial reduction of Hypoiodous acid (HIO) by the bacterium Shewanella oneidensis MR-1.
• To identify the specific microbial pathways and components involved in HIO transformation.
• To elucidate the role of HIO reduction in microbial detoxification and its impact on other iodine species.

Main Methods:

• Utilized genetic mutants of Shewanella oneidensis MR-1 with disruptions in extracellular electron transfer components.
• Quantified HIO reduction rates by wild-type and mutant strains.
• Investigated the role of outer-membrane c-type cytochromes (MtrC, OmcA) and the DmsEFAB pathway.
• Assessed the chemical reactivity of flavins with HIO.
• Examined the effect of HIO reduction on iodate reduction.

Main Results:

• Shewanella oneidensis MR-1 actively reduces HIO to iodide.
• Disruption of the MtrCAB-OmcA transmembrane electron conduit significantly impaired HIO reduction.
• Mutants lacking MtrC and OmcA showed reduced HIO reduction efficiencies.
• Flavin secretion was not essential, but reduced riboflavin chemically reduced HIO.
• HIO reduction inhibited iodate reduction, indicating a detoxification role.

Conclusions:

• Shewanella-mediated HIO reduction is a rapid detoxification pathway.
• The MtrCAB-OmcA pathway is the primary mediator of HIO reduction in S. oneidensis MR-1.
• The DmsEFAB pathway and endogenous electron shuttles play minor roles in HIO reduction.