Molecular analysis of polyphosphate accumulation in bacteria

The dynamic behavior of inorganic polyphosphate (polyP), its accumulation a nd disappearance, is the most striking aspect of polyP metabolism in bacter ia. Imbalance between polyP synthesis and degradation results in fluctuatio ns of polyP by 100- to 1000-fold. We here review recent results with respec t to this polyP metabolism in bacteria. Polyp accumulation in response to a mino acid starvation, accompanied by increased levels of stringent factors, has been observed in Escherichia coli. Inhibition by stringent factors of polyphosphatase interrupts the dynamic balance between the synthesis and de gradation of polyP, accounting for polyP accumulation. Polyphosphate kinase is required for activation of intracellular protein degradation, which is required for adaptation at the onset of amino acid starvation. The adaptati on to amino acid starvation is mediated by the network of stringent respons e and polyp metabolism. PolyP accumulation independent of stringent respons e has also been observed. Novobiocin, an inhibitor for DNA gyrase, stimulat ed accumulation of polyp but not that of stringent factors. However, a temp erature-sensitive DNA gyrase mutant did not exhibit polyP accumulation at t he non-permissive temperature. Antagonistic relationship of polyp to nuclei c acid synthesis, explored by Harold, appears to be more complicated We dis cuss relationship of P-i regulation to polyP accumulation in E. coli and Kl ebsiella aerogenes. A function of polyP as an in vivo phosphagen affecting polyP accumulation is also discussed.