The Phototrophic Way of Life / Evolutionary Considerations

The Phototrophic Way of Life / Chemotrophic Growth with O₂ / Evolutionary Considerations: "Porphyrins are found in all organisms from archaebacteria through plants to animals, and are indispensable as prosthetic groups for energy conservation. In contrast, the partially reduced derivates of porphyrins, the (bacterio)chlorophylls, are synthesized by members of only a few bacterial divisions (Fig. 1). This indicates that the capability for synthesis of porphyrins is a very ancient trait, whereas only a few prokaryotes acquired the capability to form photosynthetic pigments. Photosynthesis requires the presence of various complex protein structures and cofactors, and thus the expression of a large number of different genes (see Photosynthetic gene cluster). Previously, it had therefore appeared justified to consider all phototrophic prokaryotes as a monophyletic group only distantly related to nonphototrophic bacteria (Pfennig and Tr?per, 1974; Tr?per and Pfennig, 1978). Two lines of evidence have been used to recon struct the evolution of photosynthesis."