Polyphosphate body and acid phosphatase localization in Nostoc sp.
Polyphosphate bodies and acid phosphatase activity were characterized in Nostoc sp. to determine if the hydrolysis of polyphosphate bodies occurs during dark (energy stress) periods. Electron and light microscopy were used to locate polyphosphate bodies. Acid phosphatase activity was measured using p-nitrophenyl phosphate as the substrate to determine net changes in the level of the enzyme activity. To induce energy stress, Nostoc sp. cells were kept in the dark for 72 h to deplete stored carbon compounds. Cells incubated in the light for 72 h (controls) showed acid phosphatase activity localized around the perimeter of polyphosphate bodies. When cells were incubated in the dark, acid phosphatase activity occurred throughout the polyphosphate body matrix. However, complete hydrolysis of the polyphosphate body did not occur and the rate of acid phosphatase activity was not affected.