Immobilization results in sustained calcium transport in Nostoc calcicola Bréb

The uptake pattern of Ca2+ by the cyanobacterium Nostoc calcicola Bréb in its freely suspended and immobilized form is comprised of two distinct phages; (a) rapid uptake for 1st 10 min followed by (b) slower transport at least up to 60 min. Entrapment of cyanobacterial cells in polyvinyl foam always maintained a higher Ca2+ profile over freely suspended cells. Also, the intracellular Ca2+ concentration was three times more in the former under similar experimental conditions. Whereas, illumination supported maximum Ca2+ transport in all the sets, darkness resulted in drastic reduction (90%) of Ca2+ uptake in freely suspended cells and least (15%) in polyvinyl entrapped cyanobacterial cells. Exogenously added ATP (10 microM) on the other hand, enhanced Ca2+ uptake in dark incubated freely suspended cells; ATP at the same concentration failed to bring out any significant enhancement in cation uptake in immobilized cells facing dark exposure. It was observed that these cells were still able to sustain sufficient ATP preserves to drive active transport of Ca2+ even in the dark. Furthermore, the immobilized cells exhibited remarkable Ca2+ transport rate even at the age of 20 and 50 days at which its free living counterpart took up insignificant Ca2+. These findings suggest the improved metabolic efficiency of polyvinyl foam entrapped cells over freely suspended cells in terms of Ca2+ accumulation and its possible use as a bioreactor for metal accumulation/removal in repetitive cycles without any measurable loss in cell biomass.