Carbon Fixation; Rubisco Minireview

Photosynthesis Research

, Volume 16, Issue 1, pp 141-154

Uptake and utilization of inorganic carbon by cyanobacteria

  • John PierceAffiliated withCentral Research and Development Department, E.I. Du Pont de Nemours and Company, Experimental Station
  • , Tatsuo OmataAffiliated withSolar Energy Research Group, The Institute of Physical and Chemical Research (RIKEN)

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Abstract

In the cyanobacteria, mechanisms exist that allow photosynthetic CO2 reduction to proceed efficiently even at very low levels of inorganic carbon. These inducible, active transport mechanisms enable the cyanobacteria to accumulate large internal concentrations of inorganic carbon that may be up to 1000-fold higher than the external concentration. As a result, the external concentration of inorganic carbon required to saturate cyanobacterial photosynthesis in vivo is orders of magnitude lower than that required to saturate the principal enzyme (ribulose bisphosphate carboxylase) involved in the fixation reactions. Since CO2 is the substrate for carbon fixation, the cyanobacteria somehow perform the neat trick of concentrating this small, membrane permeable molecule at the site of CO2 fixation. In this review, we will describe the biochemical and physiological experiments that have outlined the phenomenon of inorganic carbon accumulation, relate more recent genetic and molecular biological observations that attempt to define the constituents involved in this process, and discuss a speculative theory that suggests a unified view of inorganic carbon utilization by the cyanobacteria.

Key words

carbonic anhydrase carboxysomes CO2 transport cyanobacteria inorganic carbon utilization ribulose bisphosphate carboxylase