Cyanobacteria photosynthesis

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... 

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. 

Photoautotrophic organisms, such as algae, cyanobacteria, and plants, all contain chlorophyll a and obtain energy by a process known as oxygenic photosynthesis. The overall chemical reaction of this process is ... 

A decade after the discovery of the Rieske protein in mitochondria (90), a similar FeS protein was identified in spinach chloroplasts (91) on the basis of its unique EPR spectrum and its unusually high reduction potential. In 1981, the Rieske protein was shown to be present in purified cytochrome Sg/complex from spinach (92) and cyanobacteria (93). In addition to the discovery in oxygenic photosynthesis, Rieske centers have been detected in both single-RC photosynthetic systems [2] (e.g., R. sphaeroides (94), Chloroflexus (95)) and [1] (Chlo-robium limicola (96, 97), H. chlorum (98)). They form the subject of a review in this volume. 

Cyanobacteria, prokaryotic algae that perform oxygenic photosynthesis, respond to a decrease in ambient growth temperature by desaturating the fatty acids of membrane lipids to compensate for the decrease in the molecular motion of the membrane lipids at low temperatures. During low-temperature acclimation of cyanobacterial cells, the desaturation of fatty acids occurs without de novo synthesis of fatty acids [110, 111]. All known cyanobacterial desaturases are intrinsic membrane proteins that act on acyl-Hpid substrates. 

Algae have the ability to directly utilize sunlight and carbon dioxide for photosynthesis. Due to this activity, cyanobacteria may help to solve a global environmental problem, the greenhouse effect, which increasingly threatens mankind at the beginning of the 21st century. 

Cohen Y, Jorgensen BB, Revsbech NP, et al. 1986. Adaptation to hydrogen sulfide of oxygenic and anoxygenic photosynthesis among cyanobacteria. Appl Environ Microbiol 51 398-407. 

Molecular, spectroscopic, and functional genomics studies have demonstrated the remarkable similarity among the components of the photosynthetic machinery of cyanobacteria, algae, and plants. These organisms also share the need to balance the collection of energy for photosynthesis with the threat of photodestruction. Carotenoids are central to attaining this balance. 

According to the endosymbiotic hypothesis, the eukaryotes used genes from both bacteria (alpha-protobacteria) and cyanobacteria. The first led to the development of mitochondria, the second to that of chloroplasts, i.e., cell organelles which are highly important for energy production (ATP synthesis) and photosynthesis. 

Prokaryote heterotrophs precursors of cyanobacteria. Stromatolites. Sulfur bacteria Beginning of photosynthesis Traces... 

Unlike the photosynthetic apparatus of photosynthetic bacteria, that of cyanobacteria consits of two photosystems, PS I and II, connected by an electron transport chain. The only chlorophyll present is chlorophyll a, and, therefore, chlorophylls b—d are not of interest in this article. Chlorophyll a is the principal constituent of PS I. Twenty per cent of isolated pigment-protein complexes contain one P700 per 20—30 chlorophyll a molecules the other 80% contain only chlorophyll a20). The physical and chemical properties of chlorophyll a and its role in photosynthesis have recently been described by Meeks77), Mauzerall75), Hoch60), Butler10), and other authors of the Encyclopedia of Plant Physiology NS Vol. 5. 

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.

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