Molecular Genetics and the Light Reactions of Photosynthesis
Youvan D.C., Marrs B.L.
- Exxon Research and Engineering Company, Route 22 East, Clinton Township, Annandale, NJ
08801
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- If the endosymbiotic theory is correct, we should expect to see similarities between
chloroplasts and photosynthetic bacteria. Comparison of certain protein and nucleic
acid sequences strongly suggest that one group of photosynthetic bacteria, the
cyanobacteria, is phylogenetically related to chloroplasts from higher plants.
Cyanobacteria, like chloroplasts, carry out oxygen-evolving ("water-splitting")
photosynthesis utilizing two photosystems, while some photosynthetic bacteria, for example
the green and purple bacteria, do not evolve oxygen and utilize only one photosystem
(reaction center). The relationship between the oxygen-evolving systems and the
simpler anoxygenic bacterial systems has been a topic of speculation for years. This
is a very important relationship for molecular biologists and biophysicists to understand
because many investigators study members of the purple nonsulfur bacterial genus Rhodopseudomonas
as a model system, and it behooves them to be able to answer the question, For what is
that a model?
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