Phosphate uptake in chemostat cultures of Escherichia coli K-12 subjected to periodic beta-glycerophosphate pulsing: a system for assaying alkaline phosphatase.

Limiting concentrations of beta-glycerophosphate were pulsed into chemostat cultures of Escherichia coli K-12 at intervals equal to the population doubling time. The resultant culture density fluctuations are interpreted in terms of inorganic phosphate uptake which, in this system, is a function of alkaline phosphatase activity. Information concerning in vivo alkaline phosphatase activity at suboptimal (acidic) pH with very low concentrations of substrate (beta-glycerophosphate) is obtained from kinetic analysis of uptake data.