Green Sulfur Bacteria and The Evolution of PS I
Molecular data show that PS I likely evolved from the photosystems of green-sulfur bacteria. The photosystems of green sulfur bacteria and those of cyanobacteria, algae, and higher plants are not the same, however there are many analogous functions and similar structures. Three main features are similar between the different photosystems. First, ferredoxin is able to be reduced due to a suitably high ionic concentration. Next, the electron-accepting reaction centers include iron-sulfur proteins. Last, the antenna complexes of both photosystems are constructed upon a protein subunit dimer. The photosystem of green sulfur bacteria even contains all of the same co-factors of the electron transport chain in PS I. The number and degree of similarities between the two photosystems strongly indicates that PS I is derived from the analogous photosystem of green-sulfur bacteria.
Read more about this topic: Photosystem I
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