"LiT": Regulation of 5-Aminolevulinic Acid Biosynthesis in the Bacterium Rhodobacter sphaeroides

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-15).Intellectual meritTetrapyrroles are essential biomolecules required for metabolism in all organisms. They form the basis of heme moieties, which act in energy-generating electron transfer reactions, and they also form the core of chlorophylls, which perform the major light harvesting function in photosynthesis. Thus, tetrapyrroles are indispensable for energy transformations in living systems. The proposed research investigates an important step in tetrapyrrole biosynthesis, the biosynthesis of the precursor molecule 5-aminolevulinic acid (ALA). The activity and regulation of two ALA synthase genes, hemA and hemT will be studied in the bacterium Rhodobacter sphaeroides, which is capable of harvesting both chemical and light energy and can fix both carbon and nitrogen, all processes which require tetrapyrroles. The ability to grow using distinct metabolic programs allows this organism to optimally utilize environmental resources, and not surprisingly its metabolism is exquisitely regulated in response to the environment. The proposed research will investigate regulation of hemA and hemT, including the role of novel sigma factor SigT, which is involved in hemT transcription. The significance of the presence of these two different ALA synthases as they relate to growth conditions will be tested. Experiments involve basic bacterial molecular genetics and biochemistry. The proposed studies will provide new insights into how organisms use genetic flexibility to adapt to different environments. In addition, fundamental information will be gained about regulation of gene expression and metabolism of a pathway that no doubt has been critical to the evolution of life on earth.Broader ImpactsThe difference in color of R. sphaeroides growing aerobically vs. photosynthetically provides an extraordinarily convincing demonstration of specific gene regulation. These visually observable metabolic changes in response to the environment continue to pique the curiosity and interest students. Over 38 students, the vast majority of whom are women, have worked in the lab where they have learned first-hand why basic research is important and worthwhile; nearly all have remained in science, leaving no doubt of the broader outcomes that can emerge from the proposed investigations. Support for this research will remain a cornerstone to quality classroom and lab instruction; students have self-reported being acquainted with state-of-the-art science made them more competitive for graduate and professional programs. ALA has agricultural and medical uses. Its economical production by anoxygenic phototrophic organisms has been of interest throughout the world for many years. A clearer understanding of its regulated formation and the enzymes involved, as well as energy metabolism in these cells, has and will continue to remove existing impediments to improvements in its production.