Photoautotrophy is the process by which organisms convert radiant energy into biologically useful energy and synthesize metabolic compounds using only carbon dioxide or carbonates as a source of carbon.

Keywords: photosynthesis; prokaryotes

Figure 1.

An integral membrane‐localized photosynthetic unit from an anoxygenic photosynthetic bacterium, comprising a reaction centre (RC) surrounded by 15 light‐harvesting complexes I (LHI), and each LHI surrounded by eight light‐harvesting complexes II (LHII). RC taken from Rhodopseudomonas viridis (Deisenhofer and Michel, ). Conserved helices from the L and M polypeptides of the RC are drawn. The special pair bacteriochlorophylls, and bacteriophaeophytins are also drawn. The stoichiometry is 1:15:120, for RC:LHI:LHII, respectively. Light can be captured by any of the three photosynthetic complexes. When captured by the LHII or LHI complexes the energy can resonate within the complexes until an RC0 is available, even an RC0 within a different photosynthetic unit.

Figure 2.

A water ecosystem. Gradients of light, oxygen and redox determine the localization of the different groups of photosynthetic bacteria. Oxygenic photosynthesis occurs at the surface, carried out by plants, algae and cyanobacteria. They absorb most light, leaving near IR and IR radiation to go through to the deeper layers. Anoxygenic photosynthesis, carried out by bacteria, occurs when oxygen becomes unavailable, in the deeper layers. hυ, light; IR, infrared; LH, light‐harvesting; mV, millivolts; nm, nanometres; PS, photosynthesis; RC, reaction centre. Reprinted with modifications from Pfennig with the kind permission of Plenum Press.



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Further Reading

Cogdell RJ, Monger TJ and Parson WW (1975) Carotenoid triplet states in reaction centers from Rhodopseudomonas sphaeroides. Biochimica et Biophysica Acta 408: 189–199.

Debus RJ, Feher G and Okamura MY (1985) LM complex of reaction centers from Rhodopseudomonas sphaeroides R‐26: characterization and reconstitution with the H subunit. Biochemistry 24: 2488–2500.

Kaplan S (1978) Control and kinetics of photosynthetic membrane development. In: Clayton R and Sistrom WR (eds) The Photosynthetic Bacteria, pp. 809–839. New York: Plenum Press.

Lascelles J (1978) Regulation of pyrrole synthesis. In: Clayton R and Sistrom WR (eds) The Photosynthetic Bacteria, pp. 795–808. New York: Plenum Press.

McDermott G, Prince SM, Freer AA et al. (1995) Crystal structure of an integral membrane light‐harvesting complex from photosynthetic bacteria. Nature 374: 517–521.

Paddock ML, Rongey SH, Feher G and Okamura MY (1989) Pathway of proton transfer in bacterial reaction centers: replacement of glutamic acid 212 in the L subunit by glutamine inhibits quinone (secondary acceptor) turnover. Proceedings of the National Academy of Sciences of the USA 86: 6602–6606.

van Neil CB (1944) The culture, general physiology, and classification of the non‐sulfur purple and brown bacteria. Bacteriological Reviews 8: 1–118.

Wraight CA, Cogdell RJ and Chance B (1978) Ion transport and electrochemical gradients in photosynthetic bacteria. In: Clayton R and Sistrom WR (eds) The Photosynthetic Bacteria, pp. 471–511. New York: Plenum Press.

Zeilstra‐Ryalls J, Gomelsky M, Eraso JM, Yeliseev A, O'Gara J and Kaplan S (1998) Control of photosystem formation in Rhodobacter sphaeroides. Journal of Bacteriology 180: 2801–2809.

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Eraso, Jesus M, and Kaplan, Samuel(Apr 2001) Photoautotrophy. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001424]