Structures inside rare bacteria are similar to those that power photosynthesis in plants today, suggesting the process is older than assumed. The finding could mean the evolution of photosynthesis needs a rethink, turning traditional ideas on their head. Photosynthesis is the ability to use the Sun's energy to produce sugars via chemical reactions. Plants, algae, and some bacteria today perform “oxygenic” photosynthesis, which splits water into oxygen and hydrogen to power the process, releasing oxygen as a waste product. Some bacteria instead perform “anoxygenic” photosynthesis, a version that uses molecules other than water to power the process and does not release oxygen. Scientists have always assumed that anoxygenic photosynthesis is more “primitive,” and that oxygenic photosynthesis evolved from it. Under this view, anoxygenic photosynthesis emerged about 3.5 billion years ago and oxygenic photosynthesis evolved a billion years later. However, by analysing structures inside an ancient type of bacteria, Imperial College London researchers have suggested that a key step in oxygenic photosynthesis may have already been possible a billion years before commonly thought. The new research was published online on July 24, 2019 in Trends in Plant Science. The article is titled “Evolution of Photochemical Research Centres: More Twists?” Lead author of the study, Dr. Tanai Cardona from the Department of Life Sciences at Imperial, said: "We're beginning to see that much of the established story about the evolution of photosynthesis is not supported by the real data we obtain about the structure and functioning of early bacterial photosynthesis systems." The bacteria they studied, Heliobacterium modesticaldum, is found around hot springs, soils, and waterlogged fields, where it performs anoxygenic photosynthesis.
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