Expression of a Cyanobacterial Gene Regulated by CO₂ Concentration

Abstract

Cyanobacteria, a large diverse group of photosynthetic prokaryotes, are known to possess an inducible inorganic carbon (C_i) concentrating mechanism which allows them to photosynthesize efficiently under the CO₂ limitations of their environments (1). The accumulation of a large body of physiological evidence has led to the postulation that this mechanism is comprised of several components including a CO₂ pump, a HCO₃ ⁻ pump, and the enzyme carbonic anhydrase (CA), which function in concert to supply Rubisco with saturating levels of CO₂ when C_i levels in the external medium are limiting (2). This study explores the molecular biology of the cyanobacterial response to low C_i by attempting to clone and characterize the expression of a gene which appears to be regulated by CO₂ concentration in the medium.