In their natural environments, photosynthetic organisms are often exposed to widely varied light environments. Species adapted to shade light, often found growing in lower layers of photosynthetic biofilms, must survive on filtered light alone. Filtered light is highly enriched in far-red wavelengths, which are normally unavailable for photosynthetic energy production in most oxygenic phototrophs. To overcome light limitations in filtered light environments, some species of algae and cyanobacteria utilize specialized photosynthetic pigments and antenna systems to harvest these far-red wavelengths. By sampling the natural environment and using custom-built far-red light growth chambers, I have isolated several species of oxygenic phototrophs that are capable of utilizing far-red light, and have characterized their photosynthetic antenna systems. The Eustigmatophyte alga I isolated from Forest Park, St. Louis, MO uses a red-shifted light-harvesting complex that contains Chlorophyll a as its only chlorophyll. The filamentous cyanobacterium LSP65 isolated from the underside of a lily pad in Ludington, MI, contains far-red-absorbing Chlorophyll f, with which it harvests far-red wavelengths. These far-red light-harvesting systems may play an important role in the improvement of photosynthetic light utilization in crop plants in the future
