Main bioreactions for polyphosphate (polyP) biosynthesis and degradation and accumulation levels in P . putida KT2440. (A) Organization of genes involved in polyP metabolism in P. putida. Bioreactions catalyzed by polyP kinase (Ppk) and exopolyphosphatase (Ppx, annotated as a Ppx/GppA phosphatase) are outlined along with the gene encoding the corresponding enzyme involved in that transformation step. Relevant ORFs surrounding the polyP-genes locus are rho (encoding a Rho transcriptional terminator factor), trx-2 (encoding a thioredoxin protein) and PP5218 (encoding a DedA family protein). Elements in this outline are not drawn to scale. (B) Growth curves for P. putida KT2440 (wt) and its Δppk and Δppx mutant derivatives developed under both glycolytic and gluconeogenic regimes. Experiments were conducted in M9 minimal medium with 0.2% (w/v) glucose or succinate as the sole C source as indicated in each plot. Time points in which the polyP content was assessed are identified with slanted arrows during both exponential growth (E) and in the stationary phase (S) (see below). Results represent the average of five independent replicates from at least three independent cultures, and error bars (consistently <10% of the means) are omitted here for the sake of clarity. (C) PolyP accumulation in P. putida KT2440 (wt) and its Δppk and Δppx mutant derivatives. Determinations were carried out in cells grown on M9 minimal medium with 0.2% (w/v) glucose or succinate as the sole C source as indicated in each plot either during exponential growth (E) and in the stationary phase (S). The polyP concentration was normalized to the cell dry weight (CDW) in each determination. Each bar represents the mean value of the polyP content ± SD of duplicate measurements from at least three independent experiments, and the asterisk identifies a significant difference at the P < 0.05 level (ANOVA).