Chapter 6: Oxygen-Evolving Cyanobacteria

This chapter describes photosynthetic antenna systems of cyanobacteria, with special emphasis on two points: (i) diversity of pigments and associated changes in proteins of antenna and reaction centers and (ii) stress-induced changes in antenna systems. The basic concepts of the constitution of pigment-protein complexes and energy transfer processes are very important for a general understanding of the systems. Furthermore, analyses of perturbed systems will also provide important information. After a short introduction, three kinds of photosynthetic pigments, chlorophylls, carotenoids, and phycobiliproteins, are briefly discussed with respect to their functions and diversity, including minor pigments. Secondly, we focus on the molecular architecture of the complexes and their functional relationships. A third point of the description is stress-induced changes in antenna, i.e., the iron-depleted condition, followed by considerations on changes in the stoichiometric ratio between photosystem I and photosystem II and their relevance for the antenna systems. Throughout this chapter, the evolution of cyanobacteria from anoxygenic photosynthetic bacteria is always considered as a cryptic topic, like figured bass.