Acquisition and Internalization of Copper by Methanotrophs

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Methanobactin (Mb) is a small copper-chelating molecule isolated from methanotrophic bacteria, organisms that utilize methane as their sole carbon source. Methanobactin facilitates copper uptake and may also function in regulation of methane monooxygenase (MMO) enzyme expression, catalysis by the copper-containing, particulate MMO (pMMO), and defense against copper toxicity and resultant oxidative stress. Although some insight into Cu-Mb structure and function has been gained in the past few years, major questions remain unanswered. First, Cu-Mb has only been characterized from one organism. It is not known whether Mb molecules from different species have similar structures. Cu-Mb from three types of methanotrophs will be isolated and characterized by analytical, spectroscopic, and structural methods. These data will provide insight into the structural diversity of Mb and into its role in interspecies competition for metal ions. Second, it is clear that methanotrophs secrete Mb into their growth medium when deprived of copper, but it is not known how Cu-Mb is taken back into the cell. Direct uptake of Cu-Mb will be established experimentally and a variety of biophysical, biochemical, and genetic approaches will be utilized to identify proteins involved in Cu-Mb uptake. Broader ImpactThe growth of methanotrophs, Mb isolation, and spectroscopic characterization have proven to be excellent training projects. Several undergraduate students will work on isolating Mb from different organisms. In addition to exposing undergraduates to this highly collaborative, interdisciplinary research project, underrepresented minority students will have the opportunity to participate as graduate students at Northwestern and through the Chicago State University-NU Masters to the PhD Bridge Program. An understanding of how methanotrophs acquire essential copper ions for methane oxidation will impact greenhouse gas models for various environments, particularly as pertains to acquisition of copper from mineral sources. In addition, Mb is potentially applicable in the semiconductor industry to remove copper from wastewater.