Carbon concentration mechanisms in photosynthetic microorganisms

Abstract

Unicellular green algae and cyanobacteria have mechanism to actively concentrate dissolved inorganic carbon into the cells, only if they are grown with air levels of CO₂, The carbon concentration mechanisms are commonly known as "CCM"

or "DIC-pumps". The D1C-pumps are environmental adaptation that function to actively transport and accumulate inorganic carbon (HCO₃ - and CO₂; C_i) within the cell and then uses this C_i pool to actively increase the concentration of CO₂ at the site of ribulose bisphosphate carboxylase-oxygenase (Rubisco), the primary CO₂ fixing enzyme. The current working model for dissolved inorganic carbon concentration mechanism in unicellular green algae includes several isoforms of carbonic

<span style="font-size:12.0pt;font-family:" times="" new="" roman";="" mso-fareast-font-family:hiddenhorzocr;mso-ansi-language:en-in;mso-fareast-language:="" en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">anhydrase (CA), and ATPase driven active transporters at the plasmalemma and at the inner chloroplast envelopes. In the past fifteen years, significant progress has been made in isolating and characterizing the various isoforms of carbonic anhydrase at the biochemical and molecular level. However, we have an inadequate understanding, of active transporters that are located on the plasmalemma and at the chloroplast envelopes. In this mini-review we focus on certain aspects of the induction, function and significance of the dissolved inorganic carbon concentration mechanisms in aquatic photosynthetic microorganisms.</span>