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


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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Available from: G. Dean Price
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    • "It has been reported that, in order to prevent the growth of invading microorganisms in cyanobacteria cultures, the pH can be increased towards alkalinity since many cyanobacteria can still grow despite such harsh environmental conditions (Pikuta and Hoover 2007; McGinn et al. 2011). Synechocystis possesses a CO 2 -concentrating mechanism enabling them to acquire and concentrate inorganic carbon from the extracellular environment (Badger and Price 2003). Moreover, they can also utilize HCO 3 − as carbon source, by converting it to CO 2 with the enzyme carbonic anhydrase. "
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    ABSTRACT: Culturing cyanobacteria in a highly alkaline environment is a possible strategy for controlling contamination by other organisms. Synechocystis PCC 6803 cells were grown in continuous cultures to assess their growth performance at different pH values. Light conversion efficiency linearly decreased with the increase in pH and ranged between 12.5 % (PAR) at pH 7.5 (optimal) and decreased to 8.9 % at pH 11.0. Photosynthetic activity, assessed by measuring both chlorophyll fluorescence and photosynthesis rate, was not much affected going from pH 7.5 to 11.0, while productivity, growth yield, and biomass yield on light energy declined by 32, 28, and 26 % respectively at pH 11.0. Biochemical composition of the biomass did not change much within pH 7 and 10, while when grown at pH 11.0, carbohydrate content increased by 33 % while lipid content decreased by about the same amount. Protein content remained almost constant (average 65.8 % of dry weight). Cultures maintained at pH above 11.0 could grow free of contaminants (protozoa and other competing microalgae belonging to the species of Poterioochromonas).
    Full-text · Article · Nov 2015 · Applied Microbiology and Biotechnology
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    • "To cope up with this loss, cyanobacteria developed a carbon concentrating mechanism (CCM), which involves carboxysomes and CO2:bicarbonate transporters (Rae et al., 2013). The primary function of carboxysome is to concentrate CO2 around RubisCO and reduce the efflux of CO2 (Price and Badger, 2003). Two types of carboxysomes came into existence, possibly by convergent evolution with similar designs and function but with different protein makeup. "
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    ABSTRACT: The impact of great oxidation event on RuBisCO has been tremendous. It has led to the competition between carbon dioxide and oxygen at the active site of the enzyme. Cyanobacteria developed strategies to combat this change by concentrating carbon dioxide in organelles called carboxysomes. RbcX helps in proper folding of RuBisCO by interacting with RbcL. However, it is not an absolute requirement for RuBisCO to attain proper folding only with the aid of RbcX. RbcX has a chaperone like activity. The present analysis led to the finding that cyanobacterial species lacking RbcX contain multitude of proteins showing homology to chaperone like proteins. These proteins might be playing the same role as RbcX in these cyanobacterial species to help RuBisCO acquire proper folding. Analyses also indicated that in general the rbcX motif is present between rbcL and rbcS.
    Full-text · Article · Aug 2015
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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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    DESCRIPTION: Carbon dioxide formation mirrors the final carbon oxidation steps of aerobic metabolism in microbial and mammalian cells. As a consequence CO2/HCO3- dissociation equilibria arise in fermenters by the growing culture. Anaplerotic reactions make use of the abundant CO2/HCO3- levels for refueling citric acid cycle demands and for enabling oxaloacetate derived products. At the same time CO2 is released manifold in metabolic reactions via decarboxylation activity. The levels of extracellular CO2/HCO3- depend on cellular activities and physical constraints such like hydrostatic pressures, aeration and the efficiency of mixing in large-scale bioreactors. Besides, local CO2/HCO3- levels might also act as metabolic inhibitors or transcriptional effectors triggering regulatory events inside the cells. This review gives an overview about fundamental physicochemical properties of CO2/HCO3- in microbial and mammalian cultures effecting cellular physiology, production processes, metabolic activity and transcriptional regulation.
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