POLYPHOSPHATE AS ACCUMULATOR OF PHOSPHORUS AND ENERGY

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Abstract
In resting" (cells of Mycobacterium cheslonei and M. thamnopheos) polyphosphate decreases in the presence of glucose and increases in the presence of malate. On the other hand, the ribonucleic acid (RNA) content of cells aerated in the presence of glucose is greater than that of cells aerated in the presence of malate. Dinitrophenol, an inhibitor of oxidative phosphorylation, inhibits polyphosphate accumulation. The reciprocal relationship between nucleic acid synthesis and polyphosphate accumulation is shown more clearly in "growing" mycobacterial cells. In phosphate-starved cells, aeration in Dubos-glucose medium produces a greater increment in RNA-P and deoxyribonucleic acid (DNA)-P than in Dubos-malate medium, or in Dubos-glucose or Dubos-malate medium plus azaserine (the azaserine acting as inhibitor of purine and hence nucleic acid synthesis). The increment in polyphos-phate-P in Dubos-glucose medium is smaller than that in the other cases. Thus, under conditions of growth there is a competitive relationship between nucleic acid synthesis and accumulation of polyphosphate. In cells first charged with polyphosphate containing P32 and then placed under "growing" conditions, transfer of P32 from polyphosphate to RNA-P was demonstrated. Stored polyphosphate is then utilizable for nucleic acid synthesis. In the present study the accumulation and disappearance of polyphosphate granules was followed by 3 parallel procedures: (a) cytochemical stains and light microscopy; (b) electron microscopy; and (c) chemical partitioning of P. The 3 methods lead to essentially the same interpretations of over-all events. Electron microscopy, however, permits a more precise localization within the cells of the sites of deposition of polyphosphate.