Inorganic polyphosphate: the multifunctional regulator and the guardian of environmental stresses in bacteria

Abstract:

Inorganic polyphosphate (polyP) is a linear polymer consisting of dozens to hundreds of orthophosphate residues (Pi) linked by high-energy phosphoanhydride bond. The studies have demonstrated that polyP is accumulated in bacteria under the unsuitable life conditions and endows bacteria with strong tolerance against environmental stresses, which trigger the stringent response along with the related enzymes of PPK, PPX and pppGpp. In oligotrophic environment, polyP acts as energy and Pi reservoir. More importantly, it participates in a series of starvation stress response together with RpoS, protease Lon, σ factor, etc. Such survival mechanism is similar to the life style of oligotrophic bacteria. All of these benefits from the flexibility and electron-density of polyP polymer, but its specific regulation mechanisms are still unclear. This review states the DAPI-based method to observe (fluorescent or electron microscope) and determine (fluorospectrophotometer) polyP in bacterial bodies, and mainly summarizes and analyzes the “core polyP” mechanistic alternatives in tuning microbial fitness for the adaptation under harsh living conditions.