Phosphate uptake kinetics and its regulation in N2-fixing cyanobacterium Anabaena oryzae Fritsch under salt stress

Phosphorous (P) starved cells of the cyanobacterium Anabaena oryzae showed higher phosphate uptake rates than P-sufficient cells. The P-uptake obeyed saturation kinetics. The Km value for P-deficient cells was lower (54.34 mu M) than P-sufficient cells (82.64 mu M) while V-max was higher in P-deficient and lower in P-sufficient cells. Salinity (NaCl) stimulated phosphate uptake significantly in the cyanobacterium which is followed by greater amount of P- accumulation in the form of polyphosphate bodies. Inhibition of P- uptake in P-deficient cells was 45% in dark grown compared to light grown cells. P-uptake was inhibited 52 and 85% in culture treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU; 10 mM) and carbonyl cyanide m-chloro phenylhydrazone (CCCP; 100 mM), respectively, suggesting that energy for uptake could be derived from oxidative phosphorylation and photophosphorelation.