RESEARCH

Background:

Chemical and metabolic reduction of molecular oxygen (O₂) results in the production of reactive oxygen species (ROS), including superoxide (O₂^-), hydrogen peroxide (H₂O₂), and hydroxyl radical (OH^·).  The enzymes and proteins involved in protecting aerobic organisms from oxygen toxicity include superoxide dismutase which disproportionates superoxide, catalase which removes peroxide, and peroxidases which utilize organic substrates to provide reducing power to eliminate peroxide.  However, superoxide dismutase and catalase both generate O₂ allowing for the further generation of ROS and therefore problematic for more oxygen sensitive strict anaerobes. Complete genome sequencing confirms that many strict anaerobes lack superoxide dismutase and catalase genes, although there are a few exceptions.  Evidence supports that strict anaerobes contain novel enzymes for the reduction of O₂, H₂O₂, or O₂^-, that do not catalyze the formation of O₂.  For example, Pyrococcus furiosus is a fermentative anaerobe from the Archaea domain that synthesizes superoxide reductase, which directly reduces superoxide to hydrogen peroxide.  Superoxide reductase is also called rubredoxin oxidoreductase or desulfoferrodoxin.

Research Goals:

The biochemistry and molecular biology of how anaerobic methane-producing Archaea interact with O₂ is not understood. The aim of my investigation is to use genetic, genomic, and biochemical approaches to identify and characterize novel proteins involved in oxidative stress in the methanogen, Methanosarcina acetivorans.  Along with the complete sequence of this archaeon, powerful genetic tools are available, including plasmid shuttle vectors, transformation ability, multiple selectable markers, and reporter gene fusions. The ability to perform genetic analysis, along with the complete genome sequence make M. acetivorans an excellent model organism for studying O₂ adaptation in methane-producing Archaea.