Algae. 2012; 27(4): 295-301.
Influence of CO2 concentration on carbon concentrating mechanisms in cyanobacteria and green algae: a proteomic approach
Rishiram Ramanan, Nadimuthu Vinayagamoorthy, Saravana Devi Sivanesan, Krishnamurthi Kannan, Tapan Chakrabarti
1Environmental Health Division, National Environmental Engineering Research Institute (NEERI), Nehru Marg, Nagpur 440 020, Maharashtra, India
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%) CO2 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 CO2 concentration and the repression of CCM related proteins in the sample maintained at 10% CO2. Liquid chromatography-mass spectroscopy analysis revealed the presence of two important Ci 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 CO2 concentrations and are not functional at high CO2 concentration.
Keywords : carbon concentrating mechanism (CCM); Chlorella sp.; cyanobacteria; proteomics; Rubisco; Spirulina