Search Results (109)

The linear polymer polyphosphate (polyP) is found across all three domains of life and fulfills diverse physiological functions, including phosphorus storage, chaperone activity, and stress tolerance. In bacteria, polyP synthesis is catalyzed by polyphosphate kinase (Ppk), whereas its degradation is carried out by exopolyphosphatases (Ppx). Intracellular polyP levels are determined by the balance between these opposing enzymatic activities, although the regulatory mechanisms governing this balance remain incompletely understood. In higher eukaryotes, polyP participates in diverse physiological processes from cell signaling to blood clotting. In relation to this, polyP from Levilactobacillus brevis has been identified as a protective factor against intestinal damage in a mouse model of acute colitis. Subsequent evidence has confirmed that polyP can confer beneficial effects on human intestinal health, prompting an increased interest in the production of polyP by probiotic lactic acid bacteria. Furthermore, polyP is extensively used in the food industry to enhance food quality, preservation, and nutritional value. This review summarizes the current knowledge on polyP metabolism in these bacteria and explores its functional properties and potential applications. Full article

The global market for flame-retardant materials is expected to grow steadily, from USD 7.0 billion in 2022 to USD 16.6 billion in 2030, driven by increasing demand for environment-friendly fire safety solutions in transportation, construction, and electronics. Polylactic acid (PLA), a biodegradable polymer which possesses excellent mechanical properties, is increasingly being considered for future mobility applications. However, it is characterized by high heat release and toxic smoke during combustion, which are significant drawbacks. In order to address this, the chemical modification of Kraft lignin was achieved through a phenolation and subsequent silylation with tetraethoxysilane, aiming to mitigate the degradation of PLA’s mechanical properties while utilizing its inherent char-forming ability. The modified lignins were combined with ammonium polyphosphate (APP) and melt-mixed with PLA using an injection-mixing molder to prepare test specimens. Analysis by FT-IR, NMR spectroscopy, and SEM-EDS confirmed successful grafting of phenolic and silane functionalities, and thermogravimetric analysis demonstrated enhanced thermal stability of the modified lignins compared to unmodified ones. Vertical burning tests and limiting oxygen index (LOI) measurements showed that the PLA/APP/SPKL composite material achieved a V-0 UL-94 rating and 31.95% LOI, demonstrating the highest level of flame retardancy. This compares to the LOI of neat PLA, 19 to 21%. Despite the enhancement in flame retardancy to the V-0 level, the decline in tensile strength was limited, and the composite retained comparable mechanical strength to PLA-APP composites with V-2 flame retardancy. The findings indicate that the combination of phenolation and silylation of lignin with APP, a flame-retardant material, offers a viable and sustainable methodology for the fabrication of PLA composites that exhibit both flame retardancy and mechanical strength. Full article

In this study, rice husk (RH, 15wt%) served as a carbonizing agent, and ammonium polyphosphate (APP) served as an acid and gas source. These were combined with polylactic acid (PLA) to develop a high-strength and flame-retardant PLA-based composite. The APP surface was modified with silane coupling agents (KH550 and KH570) to enhance the compatibility with the PLA matrix and improve both mechanical and flame-retardant properties. The composite was evaluated using UL-94 flame retardancy tests, limiting oxygen index (LOI) measurements, and mechanical properties assessments. The findings demonstrated that both PLA/RH-APP10% and PLA/RH-APP15% composites met the UL-94 V-0 standard. Increasing APP content enhanced flame retardancy but reduced mechanical strength. Compared to unmodified PLA composite, the PLA/KAPP5% composite exhibited an 18.7% increase in tensile strength, an elongation at break improvement from 3.26% to 4.09%, and a LOI of 27.9%. The silane modification significantly improved APP dispersion within the PLA matrix, increasing interfacial contact and improving overall mechanical properties. The flame retardancy improvements were attributed to reduced thermal decomposition rates and increased carbon residue formation. Full article

The growing use of ammonium polyphosphate (APP) fertilizer requires an understanding of its soil transformation for sustainable phosphorus (P) management and environmental protection. This study investigated the adsorption characteristics of APP1 (two P species) and APP2 (seven P species) in six soils, comparing them with monoammonium phosphate (MAP). Results revealed that APP adsorption was greater than MAP under low P soil and/or low P addition condition, but was lower under high P soil and high P addition conditions. Generally, APP1 showed greater adsorption than APP2, except in laterite soil rich in iron (Fe) and aluminum (Al) oxides. Polyphosphates in APP, especially pyrophosphate, mainly contributed to total P adsorption and promoted the release of native orthophosphate in soil. Compared to MAP, APP’s chelation altered soil pH and released Fe, Al, and organic carbon, impacting P adsorption. Redundancy analysis indicated that Fe oxide and Olsen-P in acidic soils accounted for 54.5% of the variance in adsorption differences between APP and MAP, while pH and organic matter in calcareous soils explained 49.7%. In conclusion, the adsorption differences between APP and MAP depended on P concentration, APP’s P species distribution, and soil properties, providing valuable insights for optimal P management in sustainable agriculture. Full article

Stearic acid was used to modify the surface of a mixed flame-retardant powder consisting of aluminum hydroxide and ammonium polyphosphate by an uneven nucleation method, aiming to improve its dispersion in a vinyl resin matrix. This study investigated the effect of stearic acid dosage on the powder’s surface modification, characterized by infrared spectroscopy, activation degree, and laser particle size distribution. The dispersion of the modified powder in the resin matrix was evaluated by measuring the system viscosity, scanning electron microscopy (SEM) images, and bending performance. The results indicated that when the stearic acid content was 1%, the powder exhibited the best overall coating effect, with a uniform particle size distribution and an activation degree of 73.6%. After the composite material was added to the resin, the system viscosity was 923 mPa·s, and SEM images showed good dispersion of the powder in the resin matrix. The cured resin demonstrated a bending strength of 41.86 MPa. However, the flame retardancy slightly decreased, with the limiting oxygen index (LOI) dropping from 24.6% for the unmodified sample to 24.0%. When the stearic acid content exceeded 1%, the powder’s particle size increased dramatically. Although the activation degree also increased, the improvement was not significant. The addition of the powder to the resin resulted in a higher system viscosity, and the flame retardancy deteriorated sharply, with the vertical burning rating dropping from FV-1 to FV-2. Considering flame retardancy, mechanical properties, and processing performance, the composite material with 1% stearic acid demonstrated the best overall performance. Full article

Higher demands on extreme pressure lubrication performance are posed by stringent working conditions. In this study, the synergistic tribological properties of phosphate ammonium salt in combination with active sulfurized olefin (S1) and non-active sulfurized fatty acids (S2) were investigated to meet the needs under stringent working conditions. The anti-wear mechanisms were further explored using scanning electron microscopy (SEM) with EDS, X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), and focused ion beam microscopy. The experimental results indicate that P-S2 demonstrates superior friction reduction and wear resistance under low loads, potentially attributable to its higher polarity, whereas P-S1 exhibits better wear resistance under high loads. P-S1 also shows superior extreme pressure performance attributed to its higher active sulfur content and stronger film-forming ability, evidenced by a thicker friction film (82.62 nm vs. 24.28 nm for P-S2). The study highlights that the variations in the synergistic tribological performance of phosphorus- and sulfur-based additives may link to differences in molecular structure, active sulfur content, polarity, and corrosiveness, with P-S1 demonstrating enhanced extreme pressure performance possibly through the formation of a multi-layered friction film of polyphosphate, sulfide, oligophosphate, and sulfate layers. Full article

Phosphorus is a key nutrient for all organisms. The study of phosphate metabolism and its regulation is important for understanding the evolutionary processes of regulatory systems in eukaryotic cells. The methylotrophic yeast Komagataella phaffii is an efficient producer organism, and it is actively used in biotechnological production. The high practical importance of K. phaffii has stimulated active research to find new tools to work with this yeast and optimize its cultivation conditions. In this work, we observed the effect of phosphate starvation on gene expression in K. phaffii at the transcriptome level. Phosphate starvation had a significant effect on general cell metabolism. K. phaffii cells demonstrated a response to this macronutrient deficiency through an altered gene expression of carbon and amino acid metabolism. We observed the activation of phosphate and polyphosphate metabolism gene expression. In this case, there was a suppression of ribosome biogenesis genes and genes involved in fatty acid beta-oxidation and translation processes. Full article

Polyphosphates are biopolymers composed of phosphate monomers linked by high-energy phosphoanhydride bonds. They are present across all life domains, serving as a source of energy, metal chelators, and playing a crucial role in stress defense. In Escherichia coli, polyphosphates also function as inorganic molecular chaperones. The present study aims to investigate whether polyphosphate serves a similar chaperone function in archaea, using Saccharolobus solfataricus as a model organism. To this end, polyphosphate was extracted and quantified, the ADP/ATP ratio was determined, insoluble protein extracts were analyzed at different time points after copper exposure, and qPCR was performed to measure the expression of stress-related genes. PolyP was extracted after exposing the archaeon S. solfataricus to different copper concentrations. We determined that polyP degradation is directly correlated with metal concentration. At the minimum inhibitory concentration (MIC) of 2 mM Cu²⁺, polyP degradation stabilized 2 h after exposure and showed no recovery even after 24 h. The ADP/ATP ratio was measured and showed differences in the presence or absence of polyP. The analysis of proteins precipitated under copper stress showed a higher proportion of insoluble proteins at an elevated metal concentration. On the other hand, increased protein precipitation was detected in the absence of polyP. Gene expression analysis via qPCR was conducted to assess the expression of genes involved in chaperone and chaperonin production, copper resistance, oxidative stress response, and phosphate metabolism under prolonged copper exposure, both in the presence and absence of polyP. The results indicated an upregulation of all the chaperonins measured in the presence of polyP. Interestingly, just some of these genes were upregulated in polyP’s absence. Despite copper stress, there was no upregulation of superoxide dismutase in our conditions. These results highlight the role of polyP in the copper stress response in S. solfataricus, particularly to prevent protein precipitation, likely due to its function as an inorganic chaperone. Additionally, the observed protein precipitation could be attributable to interactions between copper and some amino acids on the protein structures rather than oxidative stress induced by copper exposure, as previously described in E. coli. Our present findings provide new insights into the protective role of polyP as an inorganic chaperone in S. solfataricus and emphasize its importance in maintaining cellular homeostasis under metal stress conditions. Full article

Water exists in the beginning and hydrates all matter. Life emerged in water, requiring three essential components in compartmentalized spaces: (1) universal energy sources driving biochemical reactions and processes, (2) molecules that store, encode, and transmit information, and (3) functional players carrying out biological activities and structural organization. Phosphorus has been selected to create adenosine triphosphate (ATP) as the universal energy currency, nucleic acids for genetic information storage and transmission, and phospholipids for cellular compartmentalization. Meanwhile, proteins composed of 20 α-amino acids have evolved into extremely diverse three-dimensional forms, including folded domains, intrinsically disordered regions (IDRs), and membrane-bound forms, to fulfill functional and structural roles. This review examines several unique findings: (1) insoluble proteins, including membrane proteins, can become solubilized in unsalted water, while folded cytosolic proteins can acquire membrane-inserting capacity; (2) Hofmeister salts affect protein stability by targeting hydration; (3) ATP biphasically modulates liquid–liquid phase separation (LLPS) of IDRs; (4) ATP antagonizes crowding-induced protein destabilization; and (5) ATP and triphosphates have the highest efficiency in inducing protein folding. These findings imply the following: (1) hydration might be encoded in protein sequences, central to manifestation and modulation of protein structures, dynamics, and functionalities; (2) phosphate anions have a unique capacity in enhancing μs-ms protein dynamics, likely through ionic state exchanges in the hydration shell, underpinning ATP, polyphosphate, and nucleic acids as molecular chaperones for protein folding; and (3) ATP, by linking triphosphate with adenosine, has acquired the capacity to spacetime-specifically release energy and modulate protein hydration, thus possessing myriad energy-dependent and -independent functions. In light of the success of AlphaFolds in accurately predicting protein structures by neural networks that store information as distributed patterns across nodes, a fundamental question arises: Could cellular networks also handle information similarly but with more intricate coding, diverse topological architectures, and spacetime-specific ATP energy supply in membrane-compartmentalized aqueous environments? Full article

(1) Background: An alternative and understudied microbial mechanism that may influence demineralization is the microbially mediated ion exchange of Ca²⁺ and orthophosphate (P_i), which alters the saturation state of the mineral species within the surface enamel. There is a need to examine the ability of members of the oral microbiome to modulate Ca²⁺ and P_i, which control mineral solubility, in order to effectively evaluate mineralization therapies to improve oral health. (2) Methods: P_i uptake was measured using an ascorbic acid assay during a BHI liquid culture growth of Corynebacterium matruchotii and Streptococcus mutans for up to 20 h. The initial and endpoint medium Ca²⁺ levels were measured using ICP-OES. Bacterial cells were examined at different growth stages using DAPI/polyP binding emission at 525 nm to detect the presence of internalized macromolecules of polyphosphates (polyP) that could drive P_i uptake. (3) Results: C. matruchotii (p = 0.0061) substantially accumulated P_i (3.84 mmol/L), with a concomitant formation of polyP. In contrast, S. mutans did not take up P_i or accumulate polyP. No significant Ca²⁺ drawdown in the media was observed in either strain. (4) Conclusions: This study suggests that when examining the future efficacy of prevention technologies to improve, in vitro assays may consider including specific oral bacteria capable of substantial P_i uptake. Full article

This literature review looks at Sjogren’s Syndrome (SS), a chronic autoimmune disorder affecting exocrine glands, particularly the lacrimal and salivary glands. SS manifests as ocular and oral dryness, with severe complications like visual dysfunction and corneal perforation, as well as systemic implications, such as interstitial lung disease and lymphoma. This review explores the use of tear film biomarkers to diagnose SS, emphasizing the significance of their identification in aiding clinical diagnosis and differentiation from other diseases. This study identified and analyzed 15 papers, encompassing 1142 patients and employing various tear sample collection methods. Tear biomarkers were categorized by function and explored in-depth. Categories include (1) antimicrobials, antivirals, and antifungals; (2) components of immune regulation; (3) components that regulate metabolic processes; and (4) inflammatory markers. Noteworthy findings include the potential diagnostic values of tear lysozyme, lactoferrin, dinucleoside polyphosphates, cathepsin, defensin, antibodies, epidermal fatty acid-binding protein, HLA-DR, ADAM10, aquaporin 5, and various miRNAs and mRNAs. Overall, our understanding of SS tear film composition is enhanced, providing valuable insights into the pathogenesis of SS and offering a foundation for future diagnostic and therapeutic advancements in autoimmune conditions affecting the ocular surface. Full article

Trypanosoma cruzi is the etiologic agent of Chagas disease, an infection that can lead to the development of cardiac fibrosis, which is characterized by the deposition of extracellular matrix (ECM) components in the interstitial region of the myocardium. The parasite itself can induce myofibroblast differentiation of cardiac fibroblast in vitro, leading to increased expression of ECM. Inorganic polyphosphate (polyP) is a linear polymer of orthophosphate that can also induce myofibroblast differentiation and deposition of ECM components and is highly abundant in T. cruzi. PolyP can modify proteins post-translationally by non-enzymatic polyphosphorylation of lysine residues of poly-acidic, serine-(S) and lysine (K)-rich (PASK) motifs. In this work, we used a bioinformatics screen and identified the presence of PASK domains in several surface proteins of T. cruzi. We also detected polyP in the external surface of its different life cycle stages and confirmed the stimulation of host cell fibrosis by trypomastigote infection. However, we were not able to detect significant secretion of the polymer or activation of transforming growth factor beta (TGF-β), an important factor for the generation of fibrosis by inorganic polyP- or trypomastigote-conditioned medium. Full article

Plant senescence is a highly coordinated process that is intricately regulated by numerous endogenous and environmental signals. The involvement of phytic acid in various cell signaling and plant processes has been recognized, but the specific roles of phytic acid metabolism in Arabidopsis leaf senescence remain unclear. Here, we demonstrate that in Arabidopsis thaliana the multiple inositol phosphate phosphatase (AtMINPP) gene, encoding an enzyme with phytase activity, plays a crucial role in regulating leaf senescence by coordinating the ethylene signal transduction pathway. Through overexpressing AtMINPP (AtMINPP–OE), we observed early leaf senescence and reduced chlorophyll contents. Conversely, a loss-of-function heterozygous mutant (atminpp/+) exhibited the opposite phenotype. Correspondingly, the expression of senescence-associated genes (SAGs) was significantly upregulated in AtMINPP–OE but markedly decreased in atminpp/+. Yeast one-hybrid and chromatin immunoprecipitation assays indicated that the EIN3 transcription factor directly binds to the promoter of AtMINPP. Genetic analysis further revealed that AtMINPP–OE could accelerate the senescence of ein3–1eil1–3 mutants. These findings elucidate the mechanism by which AtMINPP regulates ethylene-induced leaf senescence in Arabidopsis, providing insights into the genetic manipulation of leaf senescence and plant growth. Full article

Ammonium polyphosphate (APP) and self-made nickel phytate (PANi) were used as modified materials to prepare green biomass rigid polyurethane foam (RPUF). The flame retardancy, thermal stability, smoke toxicity and mechanical properties of the modified RPUF were investigated by limiting oxygen index (LOI), a cone calorimetry (CONE) test, thermogravimetric analysis and a compression test. The results showed that the RPUF with 10 wt% APP (PANi/APP10) had the highest LOI of 26.5%. Its peak heat release rate (PHRR) and total heat release (THR) were reduced by 29.64% and 24.05% compared with PANi/APP0 without APP. And its smoke production rate (SPR) and total smoke release (TSR) decreased by 33.14% and 19.88%, respectively. Compared with pure RPUF, the compressive strength of PANi/APP10 was increased by 50%, mainly because APP itself was an ultra-fine powder, which was better compatible with the matrix and improved the hardness of the material. The results showed that the synergistic effect of the gas phase and the condensed phase mechanism could effectively improve the flame-retardant effect. The current research results provided a new strategy for the preparation of green and low-toxicity RPUF. Full article

Phosphorus constitutes a crucial macronutrient for crop growth, yet its availability often limits food production. Efficient phosphorus management is crucial for enhancing crop yields and ensuring food security. This study aimed to enhance the efficiency of a short-chain polyphosphate (PolyP) fertilizer by integrating it with plant growth-promoting bacteria (PGPB) to improve nutrient solubilization and wheat growth. Specifically, the study investigated the effects of various bacterial strains on wheat germination and growth when used in conjunction with PolyP. To achieve this, a greenhouse experiment was conducted in which the wheat rhizosphere was amended with a short-chain PolyP fertilizer. Based on the morphological aspect, eight bacteria, designated P1 to P8, were isolated and further characterized. Plant growth-promoting traits were observed in all bacterial strains, as they presented the ability to produce Indole Acetic Acid (IAA) in significant amounts ranging from 7.5 ± 0.3 µg/mL to 44.1 ± 2 µg/mL, expressed by B. tropicus P4 and P. soyae P1, respectively. They also produced ammonia, hydrogen cyanide (HCN), and siderophores. Their effect against the plant pathogen Fusarium culmorum was also assessed, with P. reinekei P2 demonstrating the highest biocontrol activity as it presented a total inhibitory effect. Additionally, some strains exhibited the ability to solubilize/hydrolyze phosphorus, potassium, and zinc. In vivo, the initial growth potential of wheat seeds indicated that those inoculated with the isolated strains exhibited elevated germination rates and enhanced root growth. Based on their plant growth-promoting traits and performance in the germination assay, three strains were selected for producing the best results, specifically phosphorus hydrolyzation/solubilization, zinc solubilization, IAA production, HCN, and siderophores production. Wheat seeds were inoculated by drenching in a bacterial suspension containing 10¹⁰ CFU/mL of log phase culture, and an in planta bioassay was conducted in a growth chamber using three selected strains (Pseudomonas soyae P1, Pseudomonas reinekei P2, and Bacillus tropicus P4), applied either individually or with PolyP on a P-deficient soil (28 mg/kg of P Olsen). Our findings demonstrated that the combination of Pseudomonas soyae P1 and PolyP achieved the highest shoot biomass, averaging 41.99 ± 0.87 g. Notably, applying P. soyae P1 or Bacillus tropicus P4 alone yielded similar results to the use of PolyP alone. At the heading growth stage, the combination of Bacillus tropicus P4 and PolyP significantly increased the Chlorophyll Content Index (CCI) to 37.02 µmol/m², outperforming both PolyP alone (24.07 µmol/m²) and the control (23.06 µmol/m²). This study presents an innovative approach combining short-chain PolyP with bacterial biostimulants to enhance nutrient availability and plant growth. By identifying and characterizing effective bacterial strains, it offers a sustainable alternative to conventional fertilizers. Full article