Carbon

Publisher:
Springer
Publication Type:
Chapter
Citation:
Ecology of Cyanobacteria II: Their Diversity in Space and Time, 2012, 9789400738553 pp. 443 - 460
Issue Date:
2012-07-01
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© 2012 Springer Science+Business Media B.V. All rights reserved. Summary: All cyanobacteria are actually or potentially photolithotrophic, with the exception of a recently discovered non-auotrophic free-living diazotroph which is presumably a (photo-)organotroph. Photolithotrophy involves CO 2 assimilation by Form 1A or Form 1B Rubiscos with low affinity for CO 2 and a small discrimination between CO 2 and O 2 and, at present CO 2 levels, invariably involves an inorganic carbon concentrating mechanism (CCM). About half of the cyanobacterial strains tested are facultatively photo-organotrophic, a few of which are also facultative chemo-organotrophs; the rest are obligate photolithotrophs. In the natural environment the best-established cases of photo- or chemo-organotrophy are in symbioses of diazotrophic cyanobacteria with organisms that are already photosynthetic. The quantitative contribution of dissolved organic matter to otherwise photolithotrophically growing cyanobacteria is unclear. Extent cyanobacteria are involved in both biologically mediated calcification (direct role of the organism) and biologically related calcification (indirect role of the organism). The timing of the evolution of cyanobacterial CCM is unclear: the CCM probably evolved in low-CO 2 episodes in the late Neoproterozoic or the Carboniferous, with spread to all cyanobacteria in the already established major clades by horizontal gene transfer. Cyanobacteria may be the last surviving photolithotrophs as the sun emits more energy and (by whatever mechanism) there is a decreased greenhouse gas, including CO 2 , content, of the atmosphere.
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