A photoferrotrophic bacterium (one that does photosynthesis and uses ferrous iron as a reductant) will be sought. This organism is a hypothetical phototroph that is a missing link in the evolution of the oxygen-evolving photosystem II reaction center in cyanobacteria and the distantly related quinone type reaction centers of the purple bacteria and Chloroflexus. Large differences in the sequences of the reaction center polypeptides and large gaps in the reduction potentials and hence the nature of reductants used for photosynthesis in these distantly related organisms suggest the probable existence of one or more organisms that were evolutionary intermediates in photosynthesis. Such an intermediate organism that photochemically oxidized iron would explain the geochemical appearance of oxidized iron in the Archean eon before the advent of oxygenic photosynthesis. Although intermediate organisms may have existed in the evolutionary history of the reaction center, they may be extinct today. Consequently this research is exploratory and high risk in nature. Suitable environments have been identified and will be carefully analyzed for the presence of microhabitats the could sustain photoferrrotrophy. These environments include iron-rich acid mine drainage areas, iron springs, and the sediments of shallow iron rich lakes. The microhabitats will be sought by using microelectrodes to find anoxic microzones that are exposed to light and that are high in ferrous iron, low in sulfide, and of neutral or acidic pH. Once suitable microhabitats have been found, samples will be collected for microscopy, pigment content, and culture to attempt to isolate a photoferrotroph.
