Purple bacteria photosynthetic properties

Since the first isolation of a reaction center preparation from the membrane of a facultative photosynthetic bacterium [6] our knowledge on the structure and function of these complexes has made great advances. Today the RC from purple bacteria, and particularly from the carotenoid-less strain R26 of Rhodopseudomonas sphaeroides, are by far the best known examples of photosynthetic complexes studied. Other RC from different bacteria species have also been studied and differences in components sometimes observed these differences will be mentioned below, whenever necessary, while discussing the properties of the preparations from Rp. sphaeroides R26. 

According to modern taxonomy, four divisions of photosynthetic bacteria are discerned (1) the purple bacteria, the green sulfur bacteria (Chlorobiaceae), the green filamentous (or gliding) bacteria (Chloroflexaceae) and the heliobacteria. This contribution concerns the antenna properties of the last three groups groups which have been studied less extensively than the purple bacteria, but which are not less interesting from the scientific point of view. 

The unique energetic and dynamic properties of the Bu and the 2A states of carotenoids have been discussed in relation to the light-harvesting function in purple photosynthetic bacteria (Koyama et al.. 

Evidence for the possible participation of an intermediate Chi a molecule comes from a recent ESR study (53) and an analogy with the properties of the corresponding photosystem (56) in purple photosynthetic bacteria. When the electron transfer chain on the... 

Carotenoids in aerobically grown cells of Erythrobacter sp. OCh 114 have been identified [2]. Spheroidenone is dominant, and small amounts of 2,2 -diketospirilloxanthin and OH-spheroidenone are also found. All of these carotenoids are bound to a photosynthetic reaction center or light-harvesting complexes, whose properties are similar to those of the purple photosynthetic bacteria [1]. 

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