Phosphatase Synthesis in a Citvobacter sp. Growing in Continuous Culture

SUMMARY: When a Citrobacter sp. was grown aerobically at D = 0.5 μmax in glycerol-limited chemostat culture, maximum phosphatase specific activity was obtained at 30°C and pH 7.0. This was a four-fold increase on the maximum activity obtained in batch culture and detailed tests implicated an atypical acid-type phosphatase. The activity was very resistant to cadmium, confirming an earlier postulate that a cadmium-resistant phosphatase was indispensable for the high uptakes of cadmium (as CdHPO4) obtained with this strain. Cobalt and nickel also had little effect on activity, but zinc was inhibitory at pH 7.0 and copper at pH 5.0 and 7.0. The enzyme was not activated by Mg2+ and the cells could be stored in saline for at least 17 d without any loss of phosphatase activity.