Early Evolution of Photosynthesis1
Robert E. Blankenship*
+ Author Affiliations
Departments of Biology and Chemistry, Washington University, St. Louis, Missouri 63130
Plant Physiology October 2010 vol. 154 no. 2 434-438
Photosynthesis is the only significant solar energy storage process on Earth and is the source of all of our food and most of our energy resources. An understanding of the origin and evolution of photosynthesis is therefore of substantial interest, as it may help to explain inefficiencies in the process and point the way to attempts to improve various aspects for agricultural and energy applications.
A wealth of evidence indicates that photosynthesis is an ancient process that originated not long after the origin of life and has evolved via a complex path to produce the distribution of types of photosynthetic organisms and metabolisms that are found today (Blankenship, 2002; Björn and Govindjee, 2009). Figure 1 shows an evolutionary tree of life based on small-subunit rRNA analysis. Of the three domains of life, Bacteria, Archaea, and Eukarya, chlorophyll-based photosynthesis has only been found in the bacterial and eukaryotic domains. The ability to do photosynthesis is widely distributed throughout the bacterial domain in six different phyla, with no apparent pattern of evolution. Photosynthetic phyla include the cyanobacteria, proteobacteria (purple bacteria), green sulfur bacteria (GSB), firmicutes (heliobacteria), filamentous anoxygenic phototrophs (FAPs, also often called the green nonsulfur bacteria), and acidobacteria (Raymond, 2008). In some cases (cyanobacteria and GSB), essentially all members of the phylum are phototrop2hic, while in the others, in particular the proteobacteria, the vast majority of species are not phototrophic.