• ALGAE
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• v.27 no.4
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• pp.295-301
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• 2012

Carbon concentrating mechanisms play a vital role in photosynthesis in microalgae and cyanobacteria especially in the proper functioning of Rubisco and assimilation of carbon via the Calvin cycle. This study evaluates the role of carbon dioxide on carbon concentrating mechanism (CCM) in a cynaobacteria, Spirulina platensis and a microalga, Chlorella sp. 786. The study organisms were grown in both atmospheric (control sample, 0.035%) and high (exposed sample, 10%) $CO_2$ concentrations. Second dimension (2D) electrophoresis revealed a huge difference in the protein profiles of both organisms suggesting the induction of CCM related proteins in the sample maintained at atmospheric $CO_2$ concentration and the repression of CCM related proteins in the sample maintained at 10% $CO_2$. Liquid chromatography-mass spectroscopy analysis revealed the presence of two important $C_i$ transporter proteins in the control sample of S. platensis, namely ferredoxin-$NADP^+$ reductase and ATP binding cassette (ABC) transport system protein. These proteins were only expressed in the control sample and were downregulated or not expressed at all in the exposed sample. Consequently, this study conclusively proves that CCMs are only inducted at low $CO_2$ concentrations and are not functional at high $CO_2$ concentration.

• Ocean and Polar Research
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• v.44 no.3
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• pp.209-220
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• 2022

Carbonic anhydrase (CA) is a key controller of the carbon concentrating mechanism (CCM), and is known to be affected by ambient pH and CO₂ compositions. Herein, we characterized three novel CAs genes (PmCA1, 2, and 3) from the marine dinoflagellate Prorocentrum minimum, and evaluated the relative expressions of the PmCAs and photosynthetic genes PmatpB and PmrbcL under different pH conditions. Each PmCA was predicted to have amino acid residues constituting the zinc binding site. With signal peptide, PmCA1 and PmCA2 were predicted to be intracellular CAs located in the cytoplasm and chloroplast membrane, respectively. On the other hand, PmCA3 was predicted to be extracellular CA located in the plasma membrane. Also, PmCA1 was classified into the beta family, and PmCA2 and PmCA3 were classified into the alpha family via phylogenic analysis. The photosynthesis efficiency of P. minimum was similar at pH 7 to 9, and decreased significantly at pH 6 and pH 10. Overall, relative gene expression levels of the three PmCAs decreased at low pH, and increased as pH increased. Photosynthesis related genes, PmatpB and PmrbcL, showed similar expression patterns to those of PmCAs. These results suggest that changes in seawater pH may affect photosynthesis and CO₂ metabolism in marine dinoflagellates.

• Journal of Korean Society on Water Environment
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• v.38 no.6
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• pp.282-291
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• 2022

Since the efficiency of wastewater treatment using microalgae differs depending on the metabolic characteristics of the species, it is important to understand the characteristics of target algae prior to the application in wastewater treatment. In this study, for the application of Arthrospira platensis to wastewater treatment, which is a filamentous alkaliphilic cyanobacteria, basic species specificity was identified and the possibility of application to wastewater treatment was investigated. As a result of the species specificity investigation, the specific growth rate between pH 7.0 and 11.0 showed the highest value near pH 9 at 0.25/day. The reason for the relatively low growth(0.08/day) at pH 11 was thought to be the CA(carbonic anhydrase) enzyme that is involved in carbon fixation during photosynthesis has the highest activity at pH 8.0 to 9.0, and at pH 11, CA activity was relatively low. In addition, A. platensis showed optimal growth at 400 PPFD(photosynthetic photon flux density) and 30℃, and this means that cyanobacteria such as A. platensis have a larger number of PS-I(photosystem I) than that of PS-II(photosystem II). It was speculated that it was because higher light intensity and temperature were required to sufficiently generate electrons to transfer to PS-I. Regarding the applicability of A. platensis, it was suggested that if a system using the synergistic effect of co-culture of A. platensis and bacteria was developed, a more efficient system would be possible. And different from single cocci, filamentous A. platensis expected to have a positive impact on harvesting, which is very important in the latter part of the wastewater treatment process.