Cyanobacteria evolution

During prebiotic times, water-soluble ferrous iron was present and was used in the first stage of life, while copper was in the water-insoluble Cu(I) state, as highly insoluble sulphides. About 109 years ago the metabolism of a primitive prokaryote (cyanobacteria) led to the evolution of dioxygen into the Earth s atmosphere. A... 

In this system, oxygen is produced by photosystem II, as in green plants and cyanobacteria. The photosynthetic electron transfer, via photosystem I, is linked by low-potential electron carriers to hydrogenase, which produces H2 (Fig. 10.3). Benemann and Weare (1974) then went on to investigate H2 evolution by N2-fixing cyanobacterial cultures as a whole-cell source of hydrogen energy. 

Flores, E. and Herrero, A. (1994) Molecular evolution and taxonomy of the cyanobacteria. In D. A. Bryan (ed.), The Molecular Biology of Cyanobacteria. Dordrecht, The Netherlands Kluwer Academic Publishers, pp. 487-517. 

A comparison of P7J0 in PS I from plants, green algae and cyanobacteria,204 showed only very small variations of the electronic structure, which indicates that P70o and its protein surrounding must be highly conserved in the evolution of species. 

With the evolution of cyanobacteria that produced 02 from water, the earth s atmosphere became aerobic and organisms were under selective pressure to develop aerobic metabolism, which, as we have seen, is much more efficient than anaerobic fermentation. 

Fig. 2. An evolution diagram illustrating a suggestion of common ancestry of some present-day organisms. The essential features of present-day photosynthesis may have originated in the prebiotic era and is preserved in its most primitive form in (at least some) present-day phototrophs. The heterotrophs may have developed parallel with the aerobic nonphotosynthetic bacteria, some l to 1.5 x 109 years after the emergence of the cyanobacteria. The eukaryotic photosynthetic organisms developed much later, perhaps some 1.5 to 0.5 x 109 years ago. The archaebacteria are primitive organisms that seem to have no evolutionary relation with the present prokaryotes.21 Little is known about their energy metabolism. Tentatively, they are considered as a very early form of cellular life.

Iron is concentrated most by cyanobacteria followed closely by phytoplankton (Jones et al., 1978) 7S). Copper is concentrated most by phytoplankton and next by cyanobacteria. Primitive photosynthesizers such as the cyanobacteria are especially rich in non-heme iron, which is involved in the reduction of C02, molecular nitrogen and many other substances. It has been speculated that during the evolution of the plant kingdom, the ratio of iron to other polyvalent metals decreased because the latter became more and more involved in metabolism, chiefly in oxidation reactions in the cells (Ochiai, 1983)76). Therefore, cyanobacteria contain much more iron than other plants. It has been also concluded from analyses of individual fossils that the evolution of different algal groupings in the Precambrian was accompanied by a decrease in the iron content and simultaneous enrichment in copper and others (Udel nova et al., 1981)77). Copper has been interpreted to be a marker element of the younger Proterozoic as far as its biological association is concerned. Thus, the two elements iron and copper cover the important period of the Earth s history, between 3.8 — 1.5 and 1.5 — 0.6 Ga resp. (Ochiai, 1983)76>. 

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... 

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