EFFECT OF SODIUM ON PHOSPHATE-UPTAKE IN UNICELLULAR AND FILAMENTOUS CYANOBACTERIA

The effect of Na+ on phosphate uptake was studied in four strains of c yanobacteria: Synechococcus PCC 7942, Gloeothece PCC 6501, Phormidium sp. and Chlorogloeopsis PCC 6912. Phosphate uptake was stimulated by N a+ in all cases. Li+ and K+ acted as partial analogues for Na+. Half-s aturation [K-1/2(Na+)] of phosphate uptake was reached with Na+ concen trations ranging from 317 mu M in Chlorogloeopsis to 659 mu M in Phorm idium. The concentration of phosphate required to reach half-saturatio n of phosphate uptake [K-1/2(P-i)] was not changed by the presence of Na+.