Polyphosphate formation by Acinetobacter johnsonii 210A: effect of cellular energy status and phosphate-specific transport system

In acetate-limited chemostat cultures of Acinetobacter johnsonii 210A at a dilution rate of 0.1 h(-1) the polyphosphate content of the cells increased from 13% to 24% of the biomass dry weight by glucose (100 mM), which was o nly oxidized to gluconic acid. At this dilution rate, only about 17% of the energy from glucose oxidation was calculated to be used for polyphosphate synthesis, the remaining 83% being used for biomass formation. Suspensions of non-growing, phosphate-deficient cells had a six- to tenfold increased u ptake rate of phosphate and accumulated polyphosphate aerobically up to 53% of the biomass dry weight when supplied with only orthophosphate and Mg2The initial polyphosphate synthesis rate was 98 +/- 17 nmol phosphate min(- 1) mg protein(-1). Intracellular poly-beta-hydroxybutyrate and lipids serve d as energy sources for the active uptake of phosphate and its subsequent s equestration to polyphosphate. The H+-ATPase inhibitor N,N'-dicyclohexylcar bodiimide caused low ATP levels and a severe inhibition of polyphosphate fo rmation, suggesting the involvement of polyphosphate kinase in polyphosphat e synthesis. It is concluded that, in A. johnsonii 210A, (i) polyphosphate is accumulated as the energy supply is in excess of that required for biosy nthesis, (ii) not only intracellular poly-beta-hydroxybutyrate but also neu tral lipids can serve as an energy source for polyphosphate-kinase-mediated polyphosphate formation, (iii) phosphate-deficient cells may accumulate as much polyphosphate as activated sludges and recombinants of Escherichia co li designed for polyphosphate accumulation.