Photosynthesis in cyanobacteria

Life on earth started anaerobically and anaerobic organisms flourished for more than 500 million years before oxygen became available and started to play a role in the further evolution of life (Fenchel and Finlay 1994). The evolution of photosynthesis in cyanobacteria resulted in a steady increase in the amount of oxygen in the atmosphere. This presence of oxygen opened new ways for the degradation of substrates and resulted in the evolution of aerobic energy metabolism, i.e. production of ATP. Many prokaryotes use oxygen... 

As indicated in the introduction, it is possible to carry out PAC experiments under physiological conditions, and even in vivo experiments are possible. One example of the latter is the study of the fast inhibition of photosynthesis in cyanobacteria. Photosynthesis in cyanobacteria is inhibited within about 15 min after exposure to Cd(II). Exposing the cyanobacteria to " "Cd it was possible to follow the fate of Cd(II) in terms of binding to biomolecules, as the biological... 

Padan E. (1979) Facultative anoxygenic photosynthesis in cyanobacteria. Ann. Rev. Plant Physiol. Plant Molecul. Biol. 30, 27-40. 

As noted in the previous section, photosynthesis In the green and purple bacteria does not generate oxygen, whereas photosynthesis In cyanobacteria, algae, and higher plants does. This difference Is attributable to the presence of two types of photosystem (PS) in the latter organisms PSI reduces NADP to NADPH, and PSII forms O2 from H2O. In contrast, the green and purple bacteria have only one type of photosystem, which cannot form O2. We first discuss the simpler photosystem of purple bacteria and then consider the more complicated photosynthetic machinery in chloroplasts. 

Nogales J, Gudmundsson S, Knight EM, et al Detailing the optimahty of photosynthesis in cyanobacteria through systems biology analysis, Proc Natl Acad Sci USA 109(7) 2678-2683, 2012. 

Bentley FK, Garcia-Cerdan JG, Chen H-C, Melis A (2013) Paradigm of monoterpene (-p-phellandrene) hydrocarbons production via photosynthesis in cyanobacteria. Bioenergy Res 6(3) 917-929... 

In cyanobacteria and the eukaryotic photosynthetic cells of algae and higher plants, HgA is HgO, as implied earlier, and 2 A is O,. The accumulation of O, to constitute 20% of the earth s atmosphere is the direct result of eons of global oxygenic photosynthesis. 

Z-scheme of oxygenic photosynthesis in green algae cyanobacteria, showing links to hydrogenase... 

Figure 10.3 Z-scheme of oxygenic photosynthesis in green algae and cyanobacteria, showing links to hydrogenase. Q (plastoquinone) and X (an iron-sulfur cluster) are electron acceptors from photosystems II and I, respectively.The two hydrogenases shown are the NADP-dependent bidirectional hydrogenase and a ferredoxin-dependent enzyme.

Cyanobacteria can synthesize ATP by oxidative phosphorylation or by photophosphorylation, although they have neither mitochondria nor chloroplasts. The enzymatic machinery for both processes is in a highly convoluted plasma membrane (see Fig. 1-6). Two protein components function in both processes (Fig. 19-55). The proton-pumping cytochrome b6f complex carries electrons from plastoquinone to cytochrome c6 in photosynthesis, and also carries electrons from ubiquinone to cytochrome c6 in oxidative phosphorylation—the role played by cytochrome bct in mitochondria. Cytochrome c6, homologous to mitochondrial cytochrome c, carries electrons from Complex III to Complex IV in cyanobacteria it can also carry electrons from the cytochrome b f complex to PSI—a role performed in plants by plastocyanin. We therefore see the functional homology between the cyanobacterial cytochrome b f complex and the mitochondrial cytochrome bc1 complex, and between cyanobacterial cytochrome c6 and plant plastocyanin. 

The invention of aerobic photosynthesis, the light-driven oxidation of water to oxygen, stands as one of the pivotal evolutionary innovations in the history of life on Earth. The process is carried out only at the oxygen-evolving complex (OEC) of PSII in plants and algae, as well as in cyanobacteria. Despite the biological uniqueness of water oxidation to 02, several of the core proteins of PSII have homologues in the so-called type I and type II anaerobic photosynthetic reaction... 

Scherer, S., Almon, H. Boger, P. 1988. Interactions of photosynthesis, respiration, and nitrogen fixation in cyanobacteria. Photosyn. Res. 15, 95-114. 

Cyt b-c complex forms the evolutionary link betw.een the respiratory and photosynthetic electron-transport pathways [3]. In both systems it oxidizes quinols and reduces metalloproteins while generating protonmotive force. In cyanobacteria, the Cyt /jg-/complex is shared by both respiration and photosynthesis [21]. 

Figure 3 A schematic representation of photosystems and associated standard potentials involved in oxygenic photos5mthesis in cyanobacteria (left panel) and anoxygenic photosynthesis (right panel). The flow of electrons in the...

In the early Archean before oxygenic photosynthesis evolved, cyanobacteria were limited. 

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