research Categories: >> Origin and Evolution of Photosynthesis:
Evolution of Photosynthesis and the Transition from an Anaerobic to an Aerobic World
The evolutionary development of photosynthesis is being investigated, in particular the transition from anoxygenic to oxygenic forms of photosynthesis. The approach includes detailed molecular evolution analysis of existing photosynthetic organisms, including complete genome comparisons. The deep evolutionary link between photosynthesis and nitrogen fixation will be investigated in detail to understand the nature of the primitive reductase enzymes that may have been the ancestors to both these metabolic processes. Detailed sequence comparisons of the proteins that make up the Photosystem II reaction center that is the site of oxygen evolution will be carried out to learn the evolutionary relationships between the proteins of the related but simpler complexes found in anoxygenic bacteria and the much more complex Photosystem II. Our previous work has identified the ubiquity of horizontal gene transfer among phototrophs. We now plan to extend that work to include analysis of the roles of gene recruitment and gene duplication in the evolutionary processes that led to the development of linked photosystems and the oxygenic phenotype. The unique newly discovered chlorophyll d-containing photosynthetic prokaryote Acaryochloris marina will be investigated in detail, including analysis of cyanobacterial specific biomarkers. This organism may represent a "missing link" in the evolutionary transition from the anoxygenic to the oxygenic forms of photosynthesis. We have designed a set of PCR primers that are at the same time specific for photosynthetic organisms and universal in that they will recognize all known groups of phototrophs. We will use this method with environmental samples to determine if there are additional classes of phototrophs that have not yet been recognized.