Phosphate utilization and alkaline phosphatase activity in Anacystis nidulans (Synechococcus).

Anacystis nidulans (Synechococcus) was maintained in a medium of low phosphate concentration (0.1 mM) and grew with a normal doubling time of 5 hrs at 30 degrees C. Such cultures had a normal pigment composition and alkaline phosphatase was detectable at low specific activities only. The onset of phosphate-limited growth occurred when the phosphate concentration in the medium fell to a value below 4 muM (the limit of accurate determination by the assay method used ) and resulted in increases in alkaline phosphatase activity, reaching a final 10 to 15 fold increase in specific activity after a period of several hours. Marked changes in the overall pigment composition occurred in this period of growth restriction. The addition of phosphate to such cultures resulted in a halt in synthesis of the enzyme and the restoration of normal pigmentation before growth resumed at the normal rate. Several oraganic phosphate esters could replace inorganic phosphate for growth and were also hydrolyzed by the partially purified enzyme, but growth rates were characteristically lower and the specific activity only 3 to 4 fold higher than in cultures grown in phosphate excess. Studies with the partially purified enzyme suggested that it differed in some of its properties from other alkaline phosphatases described in the literature.