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Sci Tech
Photosynthesis analysis
PHOTOSYNTHESIS IS a chemical process that transforms sunlight into chemical energy.
Biochemists now understand that this critical biological process depends on elaborate and rapid chemistry involving a series of large and complex molecules.
"History of photosynthesis's development is hard to trace," said Robert Blankenship, professor of biochemistry at Arizona State University. "There's a bewildering diversity of photosynthetic micro organisms out there that use clearly related, but somewhat different processes. They have some common threads tying them together, but it has never been clear how they relate to each other and how the process of photosynthesis started, how it developed, and how we actually wind up with two photo systems working together in more complex photosynthetic organisms."
In a paper in the journal Science, Blankenship and colleagues partially unravel this mystery through an analysis of the genomes of five basic groups of photosynthetic bacteria and the complete range of known photosynthetic processes.
The analysis revealed clear evidence that photosynthesis did not evolve through a linear path of steady change and growing complexity but through a merging of evolutionary lines that brought together independently evolving chemical systems — the swapping of blocks of genetic material among bacterial species known as horizontal gene transfer.
The team examined the genes of five already sequenced photosynthetic bacterial genomes.
The five species belong to very separate classifications, but since they share, to varying degrees, the same photosynthetic chemical systems, the team deduced that the photosynthesis-related genes must be among the shared genes.
Blankenship says different pieces of the system evolved separately in different organisms, perhaps to serve purposes different from their current function in the photosynthesis.
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