Coexistence of liquid phases in the sodium polyphosphate-chromium nitrate-water system

Polyphosphate granule biogenesis is temporally and functionally tied to cell cycle exit during starvation in Pseudomonas aeruginosa

Polyphosphate (polyP) granule biogenesis is an ancient and ubiquitous starvation response in bacteria. Although the ability to make polyP is important for survival during quiescence and resistance to diverse environmental stresses, granule genesis is poorly understood. Using quantitative microscopy at high spatial and temporal resolution, we show that granule genesis in Pseudomonas aeruginosa is tightly organized under nitrogen starvation. Following nucleation as many microgranules throughout the nucleoid, polyP granules consolidate and become transiently spatially organized during cell cycle exit. Between 1 and 3 h after nitrogen starvation, a minority of cells have divided, yet the total granule number per cell decreases, total granule volume per cell dramatically increases, and individual granules grow to occupy diameters as large as ∼200 nm. At their peak, mature granules constitute ∼2% of the total cell volume and are evenly spaced along the long cell axis. Following cell cycle exit, granules initially retain a tight spatial organization, yet their size distribution and spacing relax deeper into starvation. Mutant cells lacking polyP elongate during starvation and contain more than one origin. PolyP promotes cell cycle exit by functioning at a step after DNA replication initiation. Together with the universal starvation alarmone (p)ppGpp, polyP has an additive effect on nucleoid dynamics and organization during starvation. Notably, cell cycle exit is temporally coupled to a net increase in polyP granule biomass, suggesting that net synthesis, rather than consumption of the polymer, is important for the mechanism by which polyP promotes completion of cell cycle exit during starvation.

Polyphosphates as inorganic polyelectrolytes interacting with oppositely charged ions, polymers and deposited on surfaces: fundamentals and applications

Polyphosphates are important but neglected polyelectrolytes that play a major role in biology and in surface science for the stabilization of colloids against flocculation and for the preservation of food. They are also known as "Calgon" ® and intensively used as additives in washing powders. This review aims to review recent developments in which linear polyphosphates are used for the design of new functional coatings using sol-gel processes and layer-by-layer deposition methods. All these methods rely on the high charge density of polyphosphates as inorganic polyelectrolytes, therefore the structure and properties of these molecules are also reviewed. New perspectives will also been given for the design of stimuli responsive coatings at the tiny frontier between biology and materials science.

Metal-induced phosphate extracellular nanoparticulate formation in Ochrobactrum tritici 5bvl1

Hexavalent chromium (Cr(VI)) is a toxic environmental contaminant which detoxification consists in reduction to Cr(III). In this work, the Cr(VI)-resistant and reducing Ochrobactrum tritici 5bvl1 produced phosphate nanoparticles upon exposure to Cr(VI) and Fe(III), effectively removing chromium from solution. Under Cr(VI) stress, higher siderophore production by strain 5bvl1 was observed. Cr(VI) toxicity was decreased in presence of Fe(III), increasing the growth and Cr(VI)-reduction rates in cell cultures, lowering the amount of morphologically compromised cells and promoting chromium immobilization as insoluble extracellular phosphate complexes. The formation of phosphate nanoparticles increased with Cr(VI) and Fe(III) concentrations and was also stimulated by Ni(II). Under these experimental conditions, nanoparticle formation occurred together with enhanced inorganic phosphate consumption by cells and increased polyphosphate kinase (PPK) activity. NMR analysis of the particles showed the presence of both polyphosphate and phosphonate together with orthophosphate, and FT-IR supported these results, also showing evidences of Cr(III) coordination. This work demonstrated that O. tritici 5bvl1 possesses protection mechanisms against chromium toxicity other than the presence of the Cr(VI) pump and SOD related enzymes previously described. Future assessment of the molecular regulation of production of these nanoparticles will open new perspectives for remediation of metal contaminated environments.

Spectroscopic study and local coordination of polyphosphate colloidal systems

The interaction between metaphosphate chains and the metal ions Ca2+ and Eu3+ has been studied in water by Eu3+ luminescence, infrared absorption, and 31P NMR spectroscopy. Two main families of sites could be identified for the metal ions in the aqueous polyphosphate colloidal systems: (1) cagelike sites provided by the polyphosphate chain and (2) a family which arises following saturation of cagelike sites. Occupation of this second family leads to supramolecular interactions between polyphosphate chains and the consequent destabilization of the colloidal system. In the polyphosphate-Ca2+ system, this destabilization appears as a coacervation process. Equilibrium existing between colloidal species as a function of the compositions could be reasoned based on the spectroscopic measurements. The determination of coordination numbers and the correlation of the results with the observation of coacervates show that Eu3+ luminescence properties can be used to probe in a unique way the coacervation process.