CAREER: Sulfur Oxidation in Chlorobium tepidum, a Model Phototrophic Bacterium

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This career development plan emphasizes genome-enabled studies of microbial physiology in a non-traditional microbial model system. The research component will provide a deeper understanding of how green sulfur bacteria (Chlorobiaceae), a widespread group of anoxygenic phototrophic bacteria, oxidize reduced sulfur compounds under anaerobic conditions. Anaerobic sulfur oxidation consumes reduced sulfur compounds, which are toxic to humans and other organisms. Anaerobic sulfur oxidation is a critical part of energy generation pathways in green sulfur bacteria, but it is one of the most poorly understood functions carried out by the Chlorobiaceae. The specific genetic components required for sulfur oxidation will be identified by a molecular genetic approach in Chlorobium tepidum, a recognized model system for the Chlorobiaceae. Characterization of mutants lacking sulfur oxidation enzymes coupled with biochemical studies will detail the contributions of these enzymes to the physiology of C. tepidum. This project will develop and disseminate genetic tools that will assist in analysis of the nine other Chlorobiaceae genomes currently being sequenced.Broader impacts: An outreach component will produce a science curriculum module that satisfies national educational standards. The module will use Winogradsky columns to illustrate the dynamic interaction between microbes and their environment. One unique aspect of the project is a strong integration with the research program. This will be accomplished by using student-constructed Winogradsky columns as sources of sulfur dependent phototrophs, which will be brought into axenic culture in the PI's laboratory. These cultures will be analyzed to assess the diversity and distribution of key sulfur oxidation genes identified by the research component. Culture properties, histories, images and data will be placed on a Web site for access by participating classrooms and the general public to complete an interactive loop between university research and K-12 education.