Far-Red Light Harvesting Chlorophyll a-Containing Antenna Complexes in Enrichment Cultures of Algae

Benjamin M. Wolfa,b, Jeremy D. Kinga,b, Gregory S. Orfa,b, Dariusz Niedzwiedzkia,b,d, Haijun Liua,b, Hao Zhanga,b, Robert E. Blankenshipa,b,c
aDepartment of Biology, Washington University in St. Louis, USA; bPhotosynthetic Antenna Research Center, Washington University in St. Louis, USA; cDepartment of Chemistry, Washington University in St. Louis, USA; dPARC Ultrafast Laser Facility, USA

During photosynthesis, plants, algae, and photosynthetic bacteria capture photons using antenna complexes composed of proteins and pigments. In higher plants and most algae, the spectral range absorbed by these antennas is limited to the visible range, 400-700 nm. However, some oxygenic photosynthetic organisms, which are adapted to growing under filtered light, contain antennas that extend this range up to 50 nm further into the far-red region. Several organisms were successfully enriched using far red light selection. One of these organisms appears to contain a far-red absorbing integral membrane complex which contains only chlorophyll a and carotenoids. We have purified the complex, allowing us to analyze its structure and function biochemically and spectroscopically. This complex contains only chlorophyll a. The interaction of the chlorophyll a with the protein environment appears to lead to the red-shifted properties. Understanding how these organisms utilize far-red light will allow us to expand the spectral range of photosynthetic light harvesting in agriculturally important plants and algae. This has the potential to increase the available photons driving oxygenic photosynthesis.