The elemental composition dynamics of large polyphosphate granules in Acinetobacter strain 210A

The Composition and Implications of Polyphosphate-Metal in Enhanced Biological Phosphorus Removal Systems

The individual cellular level and quantitative Polyphosphate (PolyP)-metal compositions in EBPR (enhanced biological phosphorus removal) systems have hardly been investigated and its potential link to EBPR performance therefore remain largely unknown. In this study, we applied scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM/EDX) method that enabled detection and semiquantification of metal elemental compositions in intact intracellular PolyP granules in individual PAO (polyphosphate accumulating organism) cells. We, for the first time, revealed diverse and dynamic distributions of different metals ions in the PolyP-metal granules in different EBPR systems operated with the same influent metal composition but varying SRT of 5-30 days. We further demonstrated that the PolyP-metal composition diversity correlated with 16S rRNA gene based PAO phylogenetic diversity, suggesting the possible phylogeny-dependent PolyP-metal composition variation. The impact of PolyP metal composition in EBPR system, especially the Mg content in PolyP granules, was evidenced by the significant and strong positive correlation between PolyP-Mg content and the long-term stability of the four EBPR systems with varying SRTs. The PolyP-Mg content can therefore possibly serve as an indicator for EBPR performance monitoring. The results demonstrated that phenotyping techniques, such as PolyP-metal-based profiling, in compliment, or combined with genotyping techniques such as phylogenetic and functional gene sequencing, can provide more insights into the mechanisms and performance prediction of this important microbial ecosystem.

Biogenic Polyphosphate Nanoparticles from a Marine Cyanobacterium Synechococcus sp. PCC 7002: Production, Characterization, and Anti-Inflammatory Properties In Vitro

Probiotic-derived polyphosphates have attracted interest as potential therapeutic agents to improve intestinal health. The current study discovered the intracellular accumulation of polyphosphates in a marine cyanobacterium Synechococcus sp. PCC 7002 as nano-sized granules. The maximum accumulation of polyphosphates in Synechococcus sp. PCC 7002 was found at the late logarithmic growth phase when the medium contained 0.74 mM of KH₂PO₄, 11.76 mM of NaNO₃, and 30.42 mM of Na₂SO₄. Biogenic polyphosphate nanoparticles (BPNPs) were obtained intact from the algae cells by hot water extraction, and were purified to remove the organic impurities by Sephadex G-100 gel filtration. By using 100 kDa ultrafiltration, BPNPs were fractionated into the larger and smaller populations with diameters ranging between 30–70 nm and 10–30 nm, respectively. 4′,6-diamidino-2-phenylindole fluorescence and orthophosphate production revealed that a minor portion of BPNPs (about 14–18%) were degraded during simulated gastrointestinal digestion. In vitro studies using lipopolysaccharide-activated RAW264.7 cells showed that BPNPs inhibited cyclooxygenase-2, inducible nitric oxide (NO) synthase expression, and the production of proinflammatory mediators, including NO, tumor necrosis factor-α, interleukin-6, and interleukin-1β through suppressing the Toll-like receptor 4/NF-κB signaling pathway. Overall, there is promise in the use of the marine cyanobacterium Synechococcus sp. PCC 7002 to produce BPNPs, an anti-inflammatory postbiotic.

Biogenic Polyphosphate Nanoparticles from Synechococcus sp. PCC 7002 Exhibit Intestinal Protective Potential in Human Intestinal Epithelial Cells In Vitro and Murine Small Intestine Ex Vivo

Polyphosphates are one of the active compounds from probiotics to maintain gut health. The current research extracted and purified intact biogenic polyphosphate nanoparticles (BPNPs) from Synechococcus sp. PCC 7002 cells. BPNPs were near-spherical anionic particles (56.9 ± 15.1 nm) mainly composed of calcium and magnesium salt of polyphosphate and were colloidally stable at near-neutral and alkaline pH. BPNPs survived gastrointestinal digestion in mice and could be absorbed and transported by polarized Caco-2 cell monolayers. They dose-dependently increased the tightness of intercellular tight junction and the expression of claudin-4, occludin, zonula occludens-1, and heat shock protein 27 in Caco-2 cell monolayers. BPNPs also effectively attenuated H₂O₂-induced cell death, plasma membrane impairment, and intracellular superoxide production in NCM460 cells. In addition, they conferred resistance to H₂O₂-induced barrier disruption in freshly excised mouse small intestine. Our results suggest that BPNPs are a promising postbiotic nanomaterial with potential applications in gut health maintenance.

Size-controlled synthesis of granular polyphosphate nanoparticles at physiologic salt concentrations for blood clotting

Size-controlled granular polyphosphate (PolyP) nanoparticles were synthesized by precipitation in aqueous solutions containing physiological concentrations of calcium and magnesium. We demonstrate using dynamic light scattering (DLS) that the solubility is correlated inversely with PolyP chain length, with very long chain PolyP (PolyP1000+, more than 1000 repeating units) normally found in prokaryotes precipitating much more robustly than shorter chains like those found in human platelet dense granules (PolyP80, range 76-84 repeating units). It is believed that the precipitation of PolyP is a reversible process involving calcium coordination to phosphate monomers in the polymer chain. The particles are stable in aqueous buffer and albumin suspensions on time scales roughly equivalent to catastrophic bleeding events. Transmission electron microscopy images demonstrate that the PolyP nanoparticles are spherical and uniformly electron dense, with a particle diameter of 200-250 nm, closely resembling the content of acidocalcisomes. X-ray elemental analysis further reveals that the P/Ca ratio is 67:32. The granular nanoparticles also manifest promising procoagulant effects, as measured by in vitro clotting tests assaying contact pathway activity.

Inhibitory effect of metal ions on the poly-phosphate release from sewage sludge during thermal treatment

The purpose of this study was aimed at identifying the influence of metal cations such as Mg2+, Ca2+, Al3+ and Fe3+ on poly-phosphate (poly-P) and total phosphate (T-P) release from sewage sludge collected from wastewater treatment plant during thermal treatment at 70 degrees C for 80 min. With the addition of chelating reagent such as EDTA, release of poly-P and T-P was improved obviously during thermal treatment. Inhibitory effect of metal cations on phosphorus release was apparent by adding metal cations into sludge sample. Most of Ca, Al and Fe inside of cell could be released into the supernatant, but captured in extracellular polymeric substance (EPS); oppositely, large quantity of Mg could be released into the supernatant directly and not concentrated in EPS. Performance of sewage sludge on phosphorus release in summer and winter was different; different precipitation and temperature possibly result in this phenomenon.

Extraction of Poly-Phosphate from the Activated Sludge with Thermal Treatment for Phosphorus Recovery

Fast consumption of high quality phosphorus mines and uneven distribution in the world result in the shortage crisis for phosphorus, meanwhile lots of phosphate compounds which are discharged into nature water bodies by human beings have already induced many environmental problems. Because of this situation, phosphorus recovery from sewage sludge working in the aeration tank of wastewater treatment plant (WWTP) has been researched in the present study. Poly-phosphate (poly-P) and total phosphate (T-P) accumulated inside activated sludge could be released by thermal treatment at low temperature, 30% poly-P and 29% T-P could be released from sludge by heating at 70°C. Different kinds of pretreatments had been tested to improve phosphorus release from activated sludge in thermal treatment; addition of chelating reagent at final concentration of 2 mM before thermal treatment could improve the phosphorus release obviously, 68% poly-P and 53% T-P could be released into liquid phase. Approximately 85% T-P could be precipitated with calcium at pH 11; it was interesting to find precipitation occurred in neutral condition without pH adjustment.

Requirement of Acinetobacter junii for magnesium, calcium and potassium ions

The goal of this study was to determine the concentrations of Mg, Ca and K ions required for the formation of metabolically active population of phosphate (P)-accumulating bacterium Acinetobacter junii. The availability of Mg, Ca and K originating from natural minerals in the conditions of severe shortage of these cations was tested. In the case of shortage of Mg, Ca and K ions in wastewater the P removal was absent due to the decay of A. junii. In the cases of Mg or K shortage in wastewater the P removal was negligible due to the decay of A. junii, while Ca was not essential for the examined bacterium. The minimal required concentrations of Mg and K in synthetic wastewater were 0.64 mg Mg/mg P and 0.50 mg K/mg P. The natural zeolitized tuffs and bentonite, either in Mg, Ca or K form, successfully replaced the lack of Mg, Ca, K and trace metals in wastewater. The requirement of A. junii for examined cations was in the order: Mg>K>Ca.

Interaction mechanisms of bacterial strains isolated from extreme habitats with uranium

This paper summarizes the effect of pH on the speciation and cellular localization of uranium bound by bacterial strains isolated from the S15 deep-well montoring site, located at the Siberian radioactive subsurface depository Tomsk-7, Russia. Microbiological methods in combination with extended X-ray absorption fine structure (EXAFS) spectroscopy, transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX) were applied. EXAFS analysis showed that the cells of the two isolates, Microbacterium oxydans S15-M2 and Sphingomonas sp. S15-S1, precipitate U(VI) as m-autunite-like phase at pH 4.5, probably due to the release of inorganic phosphate from the cells as result of the microbial metabolism. However, at pH 2 uranium formed complexes with organically bound phosphates of the cell surface. The results of the EXAFS studies corroborate those found using TEM and EDX analysis. Hypotheses explaining the different coordination chemistry of uranium to bacteria as a function of pH of uranium solution in terms of solubility of m-autunite and/or microbial activity are discussed.

Interactions between calcium precipitation and the polyphosphate-accumulating bacteria metabolism

A sequencing batch reactor that is operated for biological phosphorus removal has been operated under different influent calcium concentrations to study the precipitation process and the possible effects of phosphorus precipitation in the biological phosphorus removal process. Four experiments were carried out under different influent calcium concentrations ranging from 10 to 90 g Ca m(-3). The experimental results and the equilibrium study, which are based on the saturation index calculation, confirm that the process controlling the calcium behaviour is the calcium phosphate precipitation. This precipitation takes place at two stages: initially, precipitation of the amorphous calcium phosphate, and later crystallization of hydroxyapatite. Also the accumulation of phosphorus precipitated was observed when the influent calcium concentration was increased. In all the experiments, the influent wastewater ratio P/COD was kept constant. It has been observed that, at high calcium concentration, the ratio between phosphate release and acetate uptake (P(rel)/Ac(uptake)) decreases. Changes in the polyphosphate-accumulating organism (PAO) population and in the glycogen-accumulating organism (GAO) population during the experimental period were ruled out by means of fluorescence in situ hybridization. These results could suggest that PAO are able to change their metabolic pathways based on external conditions, such as influent calcium concentration. The accumulation of phosphorus precipitated as calcium phosphate at high influent calcium concentration throughout the experimental period confirmed that phosphate precipitation is a process that can affect the PAO metabolism.

Growth of polychlorinated-biphenyl-degrading bacteria in the presence of biphenyl and chlorobiphenyls generates oxidative stress and massive accumulation of inorganic polyphosphate

Inorganic polyphosphate (polyP) plays a significant role in increasing bacterial cell resistance to unfavorable environmental conditions and in regulating different biochemical processes. Using transmission electron microscopy of the polychlorinated biphenyl (PCB)-degrading bacterium Pseudomonas sp. strain B4 grown in defined medium with biphenyl as the sole carbon source, we observed large and abundant electron-dense granules at all stages of growth and following a shift from glucose to biphenyl or chlorobiphenyls. Using energy dispersive X-ray analysis and electron energy loss spectroscopy with an integrated energy-filtered transmission electron microscope, we demonstrated that these granules were mainly composed of phosphate. Using sensitive enzymatic methods to quantify cellular polyP, we confirmed that this polymer accumulates in PCB-degrading bacteria when they grow in the presence of biphenyl and chlorobiphenyls. Concomitant increases in the levels of the general stress protein GroEl and reactive oxygen species were also observed in chlorobiphenyl-grown cells, indicating that these bacteria adjust their physiology with a stress response when they are confronted with compounds that serve as carbon and energy sources and at the same time are chemical stressors.

The microbiology of biological phosphorus removal in activated sludge systems

Activated sludge systems are designed and operated globally to remove phosphorus microbiologically, a process called enhanced biological phosphorus removal (EBPR). Yet little is still known about the ecology of EBPR processes, the microbes involved, their functions there and the possible reasons why they often perform unreliably. The application of rRNA-based methods to analyze EBPR community structure has changed dramatically our understanding of the microbial populations responsible for EBPR, but many substantial gaps in our knowledge of the population dynamics of EBPR and its underlying mechanisms remain. This review critically examines what we once thought we knew about the microbial ecology of EBPR, what we think we now know, and what still needs to be elucidated before these processes can be operated and controlled more reliably than is currently possible. It looks at the history of EBPR, the currently available biochemical models, the structure of the microbial communities found in EBPR systems, possible identities of the bacteria responsible, and the evidence why these systems might operate suboptimally. The review stresses the need to extend what have been predominantly laboratory-based studies to full-scale operating plants. It aims to encourage microbiologists and process engineers to collaborate more closely and to bring an interdisciplinary approach to bear on this complex ecosystem.

Electron-dense granules in Desulfovibrio gigas do not consist of inorganic triphosphate but of a glucose pentakis(diphosphate)

Under certain growth conditions the sulfate-reducing bacterium Desulfovibrio gigas forms electron-dense granules in the cells which had been claimed to consist of a magnesium triphosphate). We observed granules after cultivation in media with a low Fe2+ or NH4+ concentration and reinvestigated the nature of the electron-dense bodies. Energy-dispersive X-ray analysis of the granules in the cells showed that they contain large amounts of P, Mg, and K. Gel electrophoresis and chromatographic analyses of isolated granules which had been dissolved in 20 mM EDTA, however, revealed discrepancies with commercially available polyphosphates. 31P-NMR spectra also lacked the peaks in the -22-ppm region which are characteristic for inner phosphates of polyphosphates confirming that the phosphocompound as isolated from the electron-dense bodies of D. gigas did not consist of polyphosphates. Using multinuclear NMR spectroscopy we showed that the electron-dense bodies of D. gigas contained a novel metabolite which was identified as alpha-glucose 1,2,3,4,6-pentakis(diphosphate).

Biology of polyphosphate-accumulating bacteria involved in enhanced biological phosphorus removal

Recent research on the process of biological phosphorus removal in lab-scale treatment systems has indicated that: (i) the development of an actively polyP-accumulating bacterial community after the introduction of an anaerobic period may take at least 4 months; (ii) up to 80% of all aerobic bacteria isolated from these communities are able to accumulate polyP; (iii) polyP synthesized by the bacterial communities of lab-scale treatment systems is probably mainly low polymeric, not exceeding 20 P-residues, and this polyP is rapidly degraded during the anaerobic period; (iv) the enzymatic hydrolysis of polyP under anaerobic conditions is accompanied by PHB formation from exogenous acetate, reducing equivalents are provided by the degradation of carbohydrates; and (v) nitric oxide inhibits the release of phosphate under anaerobic conditions in Renpho and F&D sludges. Bacteria belonging to the genus Acinetobacter occur in a wide variety of activated sludges in which enhanced biological phosphate removal is observed. A. johnsonii 210A was studied in detail with respect to the elemental composition of polyP granules, the enzymatic synthesis and degradation of polyP, the regulation of polyP metabolism, and the transport of phosphate. A. johnsonii 210A reflects activated sludge in a number of ways as far as polyP metabolism is concerned but its polyP is highly polymeric and the phosphate efflux rate under anaerobic conditions is relatively low and not increased by exogenous acetate. In addition to Acinetobacter, other polyP-accumulating microorganisms may be involved in biological phosphorus removal. The isolation of polyP-accumulating denitrifying bacteria may well have interesting implications for a new process design in wastewater treatment systems. Further studies on the enzymes involved in polyP biosynthesis and on the uptake and efflux systems of phosphate, potassium, magnesium and lower fatty acids in pure cultures will enlarge our insight in the energetics of the metabolism of polyP. In addition, the regulation of the metabolism of polyP-accumulating organisms needs to be studied in more detail.

Properties of polyphosphatase of Acinetobacter johnsonii 210A

Polyphosphatase, an enzyme which hydrolyses highly polymeric polyphosphates to Pi, was purified 77-fold from Acinetobacter johnsonii 210A by Q-Sepharose, hydroxylapatite and Mono-Q column chromatography. The native molecular mass estimated by gel filtration and native gel electrophoresis was 55 kDa. SDS-polyacrylamide gel electrophoresis indicated that polyphosphatase of Acinetobacter johnsonii 210A is a monomer. The enzyme was specific for highly polymeric polyphosphates and showed no activity towards pyrophosphate and organic phosphate esters. The enzyme was inhibited by iodoacetamide and in the presence of 10 mM Mg2+ by pyro- and triphosphate. The apparent Km-value for polyphosphate with an average chain length of 64 residues was 5.9 microM and for tetraphosphate 1.2 mM. Polyphosphate chains were degraded to short chain polymers by a processive mechanism. Polyphosphatase activity was maximal in the presence of Mg2+ and K+.