Purple Bacteria Develops Its Own Form of "Sunscreen"

Found that specific pigments in the light harvesting complex of a photosynthetic bacterium act primarily to protect the cell from damage by excess sunlight

May aid the design of both natural and artificial light harvesting systems to minimize deleterious effects of exposure to too much light energy

• In photosynthetic organisms, carotenoids typically act as supplementary pigments to capture wavelengths of light that the major pigments can not efficiently harvest
• However, steady-state absorption and fluorescence spectra showed that carotenoids in the photosynthetic bacterium Thermochomatium tepidum play a negligible role in energy capture and transfer
• Instead, the composition and structure of the carotenoids has been optimized to protect the light harvesting complex from sun damage

The orange ring surrounding Grand Prismatic Spring, Yellowstone National Park, is due to carotenoid molecules, produced by huge mats of algae and bacteria (Photo from http://en.wikipedia.org/wiki/Carotenoid)

Reference: D. M. Niedzwiedzhi, M. Kobayashi, R. E. Blankenship, Triplet excited state spectra and dynamics of carotenoids from the thermophilic purple photosyntheticbacterium Thermochromatium tepidum, Photosynthesis Research, 107, 177-186 (2011) [DOI: 10.1007/s11120-011-9620-x].

Support: Work was performed at University of Washington University of St. Louis and supported by the Photosynthetic Antenna Research Center, an EFRC led by Robert Blankenship at Washington University in St. Louis.