Evolution of Thylakoid Structure

Abstract

Photosynthesis, an ancient process, originated among the earliest forms of life. Its broad distribution through at least half of the eubacterial phyla is an indication of this antiquity and, as stated by Woese (1987), the complexity of this process deems it unlikely that such a process arose on multiple occasions. This chapter summarizes and compares the structure of reaction centers of oxygenic photosynthetic organisms, purple bacteria, green bacteria and heliobacteria. Though there are two different types of contemporary photochemical reaction centers, recent comparative studies of structure and function revealed remarkable similarities that led to speculation of a common ancestor. A feature common to reaction centers is their association with a pigment bed that serves as a light-harvesting antenna. Evolutionary relationships of peripheral light-harvesting antenna complexes in chloroplasts also suggest a monophyletic origin of the organelle.