Addition of orthophosphate to strain 3(0) organisms previously subjected to phosphate starvation induced accumulation of inorganic polyphosphate within the organisms. With resumption of growth the polyphosphate was degraded and served as a source of nucleic acid phosphorus. During phosphate starvation the specific activity of polyphosphate kinase and inorganic polyphosphatase increased five- to tenfold while the amount of alkaline phosphatase increased 50 times. The results suggest that synthesis of polyphosphate kinase and alkaline phosphatase was subject to repression by exogenous orthophosphate. Two mutant strains blocked in polyphosphate accumulation were found to carry defects in the synthesis of these enzymes. Mutants of class Pn-1 contained normal amounts of all three enzymes, but repression of their synthesis was not annulled by phosphate starvation. Mutants of class Pn-2 contained no polyphosphate kinase. It is suggested that synthesis of polyphosphate kinase is controlled by two genes, a structural gene and a regulator gene; the latter gene also appears to control the synthesis of alkaline phosphatase and perhaps polyphosphatase. The patterns of polyphosphate accumulation under various nutritional conditions are discussed in relation to the amounts and activities of the enzymes of polyphosphate synthesis and degradation.


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