Article

Badger MR, Price GD.. CO2 concentrating mechanisms in cyanobacteria: molecular components, their diversity and evolution. J Exp Bot 54: 609-622

Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, PO Box 475, Canberra City, ACT 2601, Australia.
Journal of Experimental Botany (Impact Factor: 5.53). 03/2003; 54(383):609-22. DOI: 10.1093/jxb/erg076
Source: PubMed

ABSTRACT

Cyanobacteria have evolved an extremely effective single-cell CO(2) concentrating mechanism (CCM). Recent molecular, biochemical and physiological studies have significantly extended current knowledge about the genes and protein components of this system and how they operate to elevate CO(2) around Rubisco during photosynthesis. The CCM components include at least four modes of active inorganic carbon uptake, including two bicarbonate transporters and two CO(2) uptake systems associated with the operation of specialized NDH-1 complexes. All these uptake systems serve to accumulate HCO(3)(-) in the cytosol of the cell, which is subsequently used by the Rubisco-containing carboxysome protein micro-compartment within the cell to elevate CO(2) around Rubisco. A specialized carbonic anhydrase is also generally present in this compartment. The recent availability of at least nine cyanobacterial genomes has made it possible to begin to undertake comparative genomics of the CCM in cyanobacteria. Analyses have revealed a number of surprising findings. Firstly, cyanobacteria have evolved two types of carboxysomes, correlated with the form of Rubisco present (Form 1A and 1B). Secondly, the two HCO(3)(-) and CO(2) transport systems are distributed variably, with some cyanobacteria (Prochlorococcus marinus species) appearing to lack CO(2) uptake systems entirely. Finally, there are multiple carbonic anhydrases in many cyanobacteria, but, surprisingly, several cyanobacterial genomes appear to lack any identifiable CA genes. A pathway for the evolution of CCM components is suggested.

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    • "strain PCC7942. Two different transport mechanisms for HCO 3 − maintain with the combined action of CA elevated levels of CO2 in the carboxysomes required for efficient carbon fixation by RubisCO (Ritchie et al., 1996; Badger and Price, 2003). "
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