Inorganic polyphosphate in the origin and survival of species

Inorganic polyphosphate (poly P), in chains of tens to hundreds of phosphate residues, linked by high-energy bonds, is environmentally ubiquitous and abundant. In prebiotic evolution it could have provided a flexible, polyanionic scaffold to assemble macromolecules. It has been conserved in every cell in nature. In prokaryotes, a major poly P synthetic enzyme is poly P kinase 1 (PPK1), which is found in 100 bacterial genomes, including numerous pathogens. Null mutants of PPK1, with low poly P levels, are defective in survival: namely, they show defective responses to physical/chemical stresses and predation. Pathogens with a PPK1 deletion are defective in biofilm formation, quorum sensing, general stress and stringent responses, motility, and other virulence properties. With the exception of Dictyostelium , PPK1 is absent in eukaryotes and provides a novel target for chemotherapy that would affect both virulence and susceptibility to antibacterial compounds. Remarkably, another PPK in Dictyostelium discoideum (PPK2) is an actin-related protein (Arp) complex that is polymerized into an actin-like filament, concurrent with its reversible synthesis of a poly P chain from ATP.