Article

Plant and Soil

, Volume 230, Issue 1, pp 39-48

N2 fixation in phototrophs: adaptation to a specialized way of life

  • J.R. GallonAffiliated withBiochemistry Research Group, School of Biological Sciences, University of Wales Swansea

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Abstract

Phototrophic diazotrophs include the photosynthetic green and purple bacteria, the heliobacteria, many cyanobacteria and the unusual chlorophyll-containing rhizobia that are found in the stem nodules of Aeschynomene spp. In this review, which concentrates on cyanobacteria, the interrelations between photosynthesis and N2 fixation are discussed. Photosynthesis can, in theory, directly provide the ATP and reductant needed to support N2 fixation but the link between these two processes is usually indirect, mediated through accumulated carbon reserves. In cyanobacteria, which possess an oxygenic photosynthesis, this serves to separate the O2 that is produced by photosynthesis from the O2-sensitive nitrogenase. However, in certain circumstances, oxygenic photosynthesis and N2 fixation coexist. Under these conditions, respiratory consumption of photosynthetically generated O2 may have an important role in minimizing O2-damage to nitrogenase.

ATP and reductant cyanobacteria nitrogen fixation oxygen photosynthetic bacteria phototrophs