Studies on inorganic carbon uptake and photosynthesis in blue green alga Nostoc calcicola.

Inorganic carbon uptake and utilization efficiency of a diazotrophic cyanobacterium, Nostoc calcicola, an 'usar' land isolate and its bicarbonate resistant mutant was investigated. The wild type strain showed significantly higher rate uptake of inorganic carbon as compared to mutant strain. The rate of photosynthesis and carbohydrate content of wild type strain was higher than mutant strain at ambient atmosphere, while at higher concentrations of inorganic carbon (100-250 mM NaHCO3) mutant strain showed better response. However the photosynthetic rate and carbohydrate content of the mutant strain was higher than wild type at their respective optimal NaHCO3 concentrations (75 and 250mM, respectively). This is indicative of the mutant strain required higher level of bicarbonate in the medium for optimal activity/growth. It may be concluded that the mutant strain is defective in carbon concentrating mechanism (CCM), and may provide a useful tool in understanding of CCM in these organisms, which in turn has a huge potential to act as global CO, sink.