Search Results (174)

Objective: This study aimed to evaluate the in vitro efficacy of silver nanoparticles (AgNPs) synthesized by bioreduction using lemongrass (Cymbopogon citratus) essential oil against multidrug-resistant (MDR) bacteria isolated from an Intensive Care Unit (ICU). Methods: The essential oil was extracted and characterized by gas chromatography–mass spectrometry (GC-MS). Antioxidant activity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay, and total phenolic content. AgNPs (3 mM and 6 mM silver nitrate) were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS), zeta potential, transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy. Bacterial isolates were obtained from ICU surfaces and personal protective equipment (PPE). Results: The essential oil presented citral A, citral B, and β-myrcene as major components (97.5% of identified compounds). AgNPs at 3 mM showed smaller size (87 nm), lower Polydispersity Index (0.14), and higher colloidal stability (−23 mV). The 6 mM formulation (147 nm; PDI 0.91; −10 mV) was more effective against a strain of Enterococcus spp. resistant to all antibiotics tested. FTIR analysis indicated the presence of O–H, C=O, and C–O groups involved in nanoparticle stabilization. Discussion: The higher antimicrobial efficacy of the 6 mM formulation was attributed to the greater availability of active AgNPs. Conclusions: The green synthesis of AgNPs using C. citratus essential oil proved effective against MDR bacteria and represents a sustainable and promising alternative for microbiological control in healthcare environments. Full article

In this study, a Ag/ZrO₂ hybrid coating prepared by the sol–gel method on a β-type Ti45Nb alloy was applied by the spin coating technique, and the microstructural, mechanical, electrochemical, and tribological properties of the surface were evaluated in a multi-dimensional manner. The hybrid solution was prepared using zirconium propoxide and silver nitrate and stabilized through a low-temperature two-stage annealing protocol. The crystal structure of the coating was determined by XRD, and the presence of dense tetragonal ZrO₂ phase and crystalline Ag phases was confirmed. SEM-EDS analyses revealed a compact coating structure of approximately 1.8 µm thickness with homogeneously distributed Ag nanoparticles on the surface. As a result of the electrochemical corrosion tests, it was determined that the open circuit potential shifted to more noble values, the corrosion current density decreased, and the corrosion rate decreased by more than 70% on the surfaces where the Ag/ZrO₂ coating was applied. In the tribological tests, a decrease in the coefficient of friction, narrowing of wear marks, and significant reduction in surface damage were observed in dry and physiological (HBSS) environments. The findings revealed that the Ag/ZrO₂ hybrid coating significantly improved the surface performance of the Ti45Nb alloy both mechanically and electrochemically and offers high potential for biomedical implant applications. Full article

Soil salinization severely limits global agricultural sustainability, particularly across the saline–alkaline landscapes of the Qinghai–Tibet Plateau. We examined how potassium fulvate (PF) modulates oat (Avena sativa L.) performance, soil chemistry, and rhizospheric microbiota in the saline–alkaline soils of the Qaidam Basin. PF markedly boosted shoot and root biomass, with the greatest response observed at 150 kg hm⁻². At the same time, it enhanced soil fertility by increasing organic matter, nitrate-N, ammonium-N, and available potassium, and improved ionic balance by lowering Na⁺ concentrations and the sodium adsorption ratio (SAR), while increasing Ca²⁺ levels and soil moisture content. Under the high-dose treatment (F2), endogenous fungal contributions declined sharply, exogenous replacements increased, and fungal α-diversity fell; multivariate ordinations confirmed that PF reshaped both bacterial and fungal communities, with fungi exhibiting the stronger response. We integrated three machine learning algorithms—least absolute shrinkage and selection operator (LASSO), Random Forest (RF), and eXtreme Gradient Boosting (XGBoost)—to minimize the bias inherent in any single method. We identified microbial β-diversity, organic matter, and Na⁺ and Ca²⁺ concentrations as the most robust predictors of the Soil Salinization and Alkalization Index (SSAI). Structural equation modeling further showed that PF mitigates salinity chiefly by improving soil physicochemical properties (path coefficient = −0.77; p < 0.001), with microbial assemblages acting as key intermediaries. These findings provide compelling theoretical and empirical support for deploying PF to rehabilitate saline–alkaline soils in alpine environments and offer practical guidance for sustainable land management in the Qaidam Basin. Full article

The Qinghai–Tibet Plateau is a key region for biodiversity conservation, where alpine grasslands are ecologically important. While previous studies have mainly addressed vegetation, ecosystem processes, and soil microbes, phyllosphere microorganisms are essential for nutrient cycling, plant health, and stress tolerance. However, their communities remain poorly understood compared to those in soil. The relative influence of host identity and environmental conditions on shaping phyllosphere microbial diversity and community assembly remains uncertain. In this study, we characterized phyllosphere bacterial and fungal communities of the phyllosphere at two alpine steppe sites with similar vegetation but climatic conditions: the Qilian Mountains (QLM) and the Qinghai Lake region (LQS). At both sites, Cyanobacteriota and Ascomycota were the predominant bacterial and fungal taxa, respectively. Microbial α-diversity did not differ significantly between the two regions, implying that host-associated mechanisms may stabilize within-site diversity. In contrast, β-diversity exhibited clear spatial differentiation. In QLM, bacterial β-diversity was significantly correlated with mean annual precipitation, while fungal α- and β-diversity were associated with soil nutrient levels (including nitrate, ammonium, available potassium, and phosphorus) and vegetation coverage. At LQS, the β-diversity of both bacterial and fungal communities was strongly influenced by soil electrical conductivity, and fungal communities were further shaped by vegetation cover. Community assembly processes were predominantly stochastic at both sites, although deterministic patterns were more pronounced in QLM. Variability in moisture availability contributed to random bacterial assembly at LQS, while increased environmental heterogeneity promoted deterministic assembly in fungal communities. The elevated diversity of microbes and plants in QLM also reinforced deterministic processes. Overall, our findings support a host–environment interaction hypothesis, indicating that host factors primarily govern α-diversity, while climatic and soil-related variables have stronger effects on β-diversity and microbial assembly dynamics. These insights advance our understanding of how phyllosphere microbial communities may respond to environmental change in alpine ecosystems. Full article

Natural and planted forests differentially regulate soil quality through vegetation–soil interactions. The effects of four types of planting covers on soil nutrients, enzyme activities, and microbial communities in the Guangxi Camellia nitidissima National Nature Reserve were studied, revealing the multi-dimensional influences of natural (broadleaf, shrubland) and planted forests (bamboo, pine) on soil quality. Surface soils (0–10 cm depth) were characterized for physicochemical properties (pH, TC, TN, NO₃⁻-N, AP), enzyme activities (α-amylase, urease, phosphatase, β-glucosidase), and microbial composition (using 16S rRNA and ITS region sequencing). Mantel tests and PLS–PM modeling were employed to investigate interactions among vegetation, soil variables, and microbes. Natural forests exhibited higher pH, nitrate nitrogen, and enzymatic activities (urease, phosphatase, β-glucosidase) alongside enhanced carbon–nitrogen accumulation and reduced acidification. Planted forests showed elevated available phosphorus and nutrient supply but lower organic matter retention. Microbial communities displayed higher similarity within natural forests, with fungal composition strongly linked to total carbon/nitrogen (p < 0.05). Vegetation type positively influenced bacterial diversity but negatively affected fungal communities. Natural forests maintained critical soil–microbe–plant interactions supporting ecosystem resilience through carbon–nitrogen cycling, while planted forests fostered divergent microbial functionality despite short-term nutrient benefits. These findings underscore natural forests’ unique role in preserving ecological stability and reveal fundamental limitations of artificial systems in mimicking microbially-mediated biogeochemical processes. Conservation policy should prioritize the protection of natural forests while simultaneously integrating microbial community management with vegetation restoration efforts to enhance long-term ecosystem functionality and nutrient cycling efficiency. Full article

This study investigates the potential of a biostimulant derived from the invasive brown alga Rugulopteryx okamurae (RoB) to enhance lettuce growth and improve its phytochemical profile. The extraction of the biostimulant was optimized through the implementation of a Box–Behnken design, and the resulting extract was then compared with a commercial Ascophyllum nodosum-based product (AnB). This comparison was made under both optimal and suboptimal fertigation conditions in a controlled, soilless culture. Lettuce plants were monitored for water and nutrient uptake, growth parameters, and accumulation of key phytochemicals such as carotenoids, tocols, sterols, and squalene. RoB significantly increased fresh and dry biomass, with enhanced nitrate and potassium uptake, in comparison to standard nutrient solution controls (p < 0.05). Treatments incorporating RoB consistently resulted in higher concentrations of lutein, β-sitosterol, and squalene, particularly under suboptimal conditions (p < 0.05), thus suggesting a strong biostimulant effect that mitigates nutrient stress. Furthermore, principal component analysis demonstrated that biostimulant application induces distinct metabolic profiles, highlighting the coordinated regulation of antioxidant pigments and sterol compounds. The findings support the dual benefits of algae-derived biostimulants in promoting sustainable crop production by improving yield quality and increasing health-promoting phytochemicals, paving the way for innovative, eco-friendly fertilization practices in modern agriculture. Full article

Soil nitrogen (N) is critical for crop yield. Although previous studies have shown that straw return enhances soil mineral N availability, the response of soil aggregate microbes to straw return and its impact on soil mineral N availability remains unclear. We conducted a 13-year experiment to explore how soil N mineralization potential, fungi, and bacteria within soil aggregates responded to straw return. Our findings indicated that straw return significantly increased mineral N concentrations in soil macroaggregates, with no statistically significant effect observed on microaggregate composition. We observed increased microbial community α-diversity, enhanced co-occurrence network stability, and an increase in functional groups associated with N (nitrate respiration, denitrification, nitrite denitrification) and carbon (saprotrophs, saprotroph–symbiotrophs, patho-saprotrophs) cycling within the aggregates. Additionally, microorganisms in macroaggregates were influenced by total N, while those in microaggregates were affected by soil total organic carbon and C–N ratio. A sensitivity network analysis identified specific microorganisms responding to straw return. Within macroaggregates, microbial community shifts explained 42.88% of mineral N variation, with bacterial and fungal β-diversity contributing 27.82% and 12.58%, respectively. Moreover, straw return upregulated N-cycling genes (N ammonification: sub, ureC, and chiA; nitrification: amoA-AOB; denitrification: nirK, nirS, nosZ, norB, and narG; and N fixation: nifH) in macroaggregates. Partial least squares path modeling revealed that N availability in macroaggregates was mainly driven by ammonification, with bacterial β-diversity explaining 23.22% and fungal β-diversity 15.16% of the variation. Our study reveals that macroaggregates, which play a crucial role in soil N supply, are highly sensitive to tillage practices. This finding provides a practical approach to reducing reliance on synthetic N fertilizers by promoting microbial-mediated N cycling, while sustaining high crop yields in intensive agricultural systems. Full article

Background: Consumers are increasingly interested in healthier, less processed food products, driving the meat industry to improve the quality and health benefits of its offerings. Growing concerns about additives and allergens have encouraged the replacement of these ingredients with natural alternatives, presenting both challenges and opportunities. However, consumer rejection of additives and the actual health effects of their replacement remain poorly understood. In previous work, two new meat products—cooked turkey breast and cooked ham—were developed, where additives and allergens were replaced with natural extracts. These products demonstrated potential health benefits in vitro, including improvements in protein quality and microbiota composition. Methods: This study assessed consumer perceptions of additives through a survey and evaluated the two new meat products in a double-blind, randomized clinical trial conducted over a 5-week period. Biomarkers of interest were measured in blood, faeces, and urine samples at baseline and at the end of this study. Additionally, a separate study tested the satiating effect of these products using VAS score surveys. Results: The additive perception survey revealed that consumers associate additive-free products with being more natural and less harmful to health, with differences observed based on age, gender, and knowledge of additives. In the clinical trial, both the intervention and control groups showed significant decreases in serum levels of ox-LDL and GPx, with no differences between the groups. However, significant differences between the groups were found in inflammation markers TNF-α and IL-1β. Furthermore, the intervention group exhibited a significant reduction in nitrate excretion and a decrease in nitrification-related gut bacteria. Finally, the reformulated products demonstrated a satiating effect, reducing hunger. Conclusions: These findings suggest that the new additive- and allergen-free reformulated meat products may offer potential oxidative and anti-inflammatory benefits to consumers. Full article

Colloidal noble metal nanoparticle aggregates have demonstrated significant advantages in surface-enhanced Raman scattering (SERS) analysis, particularly for online detection, due to their excellent optical properties, spatial homogeneity, and fluidic compatibility. However, conventional chemically induced aggregation methods (such as salt-induced nanoparticle aggregation) suffer from uncontrolled aggregation, limited stability, and narrow detection windows, which restrict their quantitative and long-term applications. In this study, we developed a non-chemical method for fabricating stable colloidal aggregates from uniform β-cyclodextrin-stabilized silver nanoparticles (β-CD@AgNPs) via centrifugation. By precisely controlling the addition rate of silver nitrate, we synthesized β-cyclodextrin-stabilized silver nanoparticles with a uniform size. Surprisingly, these nanoparticles can form highly dispersed and homogeneous colloidal aggregates simply via centrifugation, which is completely different from the behavior of traditional ligand-modified nanoparticles. Notably, the resulting aggregates exhibit excellent SERS enhancement, enabling the sensitive detection of various dyes at nanomolar levels. Furthermore, they maintain a stable SERS signal (RSD = 6.99%) over a detection window exceeding 1 h, markedly improving signal stability and reproducibility compared with salt-induced aggregates. Additionally, using pyocyanin as a model analyte, we evaluated the quantitative performance of these aggregates (LOD = 0.2 nM), achieving satisfactory recovery (82–117%) in spiked samples of drinking water, lake water, and tap water. This study provides a facile strategy for fabricating stable colloidal SERS substrates and paves the way for the advancement of SERS applications in analytical sciences. Full article

Macrotermes barneyi is a typical fungus-growing termite that forms both monogynous (single queen) and polygynous (multiple queen) colonies in nature. This species influences the local soil fertility in part by redistributing nutrients across the landscape in its habitats. However, how the colony structure of M. barneyi affects nutrient cycling and microbial communities within the nest is not well understood. In this study, we compared the physicochemical properties and microbial communities across nest parts between monogynous and polygynous colonies of M. barneyi. Our results showed that the fungus garden is the most nutrient-rich part of the nest, with higher soil moisture, organic matter, ammonium nitrogen, nitrate nitrogen, available sulfur, available potassium, available silicon, and available boron than other nest parts. Notably, the fungus garden in monogynous colonies had higher nitrate nitrogen, available sulfur, and available silicon than those in the polygynous colonies. The microbial α-diversity in the fungus garden was lower than that in other parts of the nest. β-diversity analysis revealed a clear separation of microbial communities between monogynous and polygynous colonies across nest parts. Furthermore, the relative abundance of functional genes associated with “cell cycle control, cell division, and chromosome partitioning” was higher in the fungus garden of polygynous colonies compared to monogynous colonies. Our results suggest that the fungus garden plays a crucial role in maintaining colony stability in M. barneyi colonies. The rapid depletion of nutrients in the fungus garden to sustain the larger population in polygynous colonies likely influences microbial community dynamics and nutrient cycling. Full article

The phyllosphere microbiome of aquatic macrophytes constitutes an integral component of freshwater ecosystems, serving crucial functions in global biogeochemical cycling and anthropogenic pollutant remediation. In this study, we examined the assembly mechanisms of epiphytic bacterial communities across four phylogenetically diverse macrophyte species (Scirpus validus, Hippuris vulgaris, Nymphoides peltatum, and Myriophyllum spicatum) inhabiting Ningwu Mayinghai Lake (38.87° N, 112.20° E), a vulnerable subalpine freshwater system in Shanxi Province, China. Through 16S rRNA amplicon sequencing, we demonstrate marked phyllospheric microbiome divergence, as follows: Gammaproteobacteria dominated S. validus, H. vulgaris and N. peltatum, while Alphaproteobacteria dominated in M. spicatum. The nitrate, nitrite, and pH value of water bodies and the chlorophyll, leaf nitrogen, and carbon contents of plant leaves are the main driving forces affecting the changes in the β-diversity of epiphytic bacterial communities of four plant species. The partitioning of assembly processes revealed that deterministic dominance governed S. validus and M. spicatum, where niche-based selection contributed 67.5% and 100% to community assembly, respectively. Conversely, stochastic processes explained 100% of the variability in H. vulgaris and N. peltatum microbiomes, predominantly mediated by dispersal limitation and ecological drift. This investigation advances the understanding of microbial community structural dynamics and diversity stabilization strategies in aquatic macrophyte-associated microbiomes, while establishing conceptual frameworks between plant–microbe symbiosis and the ecological homeostasis mechanisms within vulnerable subalpine freshwater ecosystems. The empirical references derived from these findings offer novel perspectives for developing conservation strategies aimed at sustaining biodiversity equilibrium in high-altitude lake habitats, particularly in the climatically sensitive regions of north-central China. Full article

Atmospheric intermediate volatile organic compounds (IVOCs) are important precursors of secondary organic aerosols (SOAs), and in-depth research on them is crucial for atmospheric pollution control. This review systematically synthesizes global advancements in understanding IVOC sources, emissions characterization, compositional characteristics, ambient concentrations, SOA contributions, and health risk assessments. IVOCs include long-chain alkanes (C₁₂~C₂₂), sesquiterpenes, polycyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons, phenolic compounds, ketones, esters, organic acids, and heterocyclic compounds, which originate from primary emissions and secondary formation. Primary emissions include direct emissions from anthropogenic and biogenic sources, while secondary formation mainly results from radical reactions or particulate surface reactions. Recently, the total IVOC emissions have decreased in some countries, while emissions from certain sources, such as volatile chemical products, have increased. Ambient IVOC concentrations are generally higher in urban rather than in rural areas, higher indoors than outdoors, and on land rather than over oceans. IVOCs primarily generate SOAs via oxidation reactions with hydroxyl radicals, nitrate radicals, the ozone, and chlorine atoms, which contribute more to SOAs than traditional VOCs, with higher SOA yields. SOA tracers for IVOC species like naphthalene and β-caryophyllene have been identified. Integrating IVOC emissions into regional air quality models could significantly improve SOA simulation accuracy. The carcinogenic risk posed by naphthalene should be prioritized, while benzo[a]pyrene requires a combined risk assessment and hierarchical management. Future research should focus on developing high-resolution online detection technologies for IVOCs, clarifying the multiphase reaction mechanisms involved and SOA tracers, and conducting comprehensive human health risk assessments. Full article

Isoconazole nitrate (ISN) is a broad-spectrum antifungal agent whose therapeutic potential is limited by poor aqueous solubility and low bioavailability. This study aimed to enhance the solubility and physicochemical properties of ISN through the formation of inclusion complexes with methyl-β-cyclodextrin (M-β-CD) using freeze-drying (FD) and spray-drying (SD) methods. The prepared inclusion complexes were comprehensively characterized by high-performance liquid chromatography (HPLC), phase solubility analysis, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), and proton nuclear magnetic resonance (¹H-NMR). Phase solubility studies revealed an AL-type solubility diagram with a 1:1 molar ratio and an apparent stability constant (K_S) of 2711 M⁻¹. Structural and thermal analyses confirmed successful inclusion complex formation and reduced crystallinity. The solubility assessment showed that ISN/M-β-CD complexes prepared by SD exhibited an approximately seven-fold higher aqueous solubility than ISN and performed better than those prepared by FD. Moreover, SD complexes demonstrated a higher drug content. These findings highlight the potential of M-β-CD-based inclusion complexation, particularly via spray-drying, as an effective strategy to enhance the solubility and bioavailability of poorly water-soluble drugs, such as ISN. Full article

Vitamin C industrial residue after evaporation (RAE) acts as both a rapid-release carbon source and a microbial activity promoter. A two-year maize field experiment assessed the effectiveness of RAE in improving soil quality in degraded semi-arid regions. The RAE formulation was applied via drip irrigation during the sixth true leaf unfolded (BBCH 24), fourteenth true leaf unfolded (BBCH 38), and middle of grain filling (BBCH 66) stages, which consisted of three treatments: (1) untreated control (CK), (2) low RAE rate (LR: 150 L/ha), and (3) high RAE rate (HR: 300 L/ha). Soil physicochemical properties, enzyme activities, maize nutrient accumulations, and yields were comprehensively analyzed at the maize maturity stage. RAE application significantly improved the following soil nutrients: dissolved organic carbon (10.40–25.92%), ammonium nitrogen (14.04–70.67%), nitrate nitrogen (14.80–78.63%), and available phosphorus (11.79–42.55%). Soil enzyme activities also increased: sucrase (12.38–30.25%), amidase (1.95–25.69%), peptidase (0.56–48.79%), β-1,4-N-acetylglucosaminidase (3.11–9.48%), protease (17.41–226.29%), and acid phosphatase (8.73–60.04%). These changes enhanced maize nitrogen (17.63–40.73%) and phosphorus (20.09–42.11%) uptake, increasing yield by 7.12–13.46%. Statistical analysis showed strong correlations between yields and nutrient accumulations (r = 0.82, p < 0.01), particularly phosphorus (r = 0.91, p < 0.001). RAE enhances crop productivity in degraded agricultural systems by improving soil nutrient availability and plant assimilation, making it a viable alternative to conventional fertilizers. Full article

The synthesis of nitrate (NO₃⁻) via electrocatalytic nitric oxide oxidation reaction (NOOR) is a green and efficient strategy for nitrogen fixation, which has great advantages over conventional nitrate synthesis. Notably, it also presents a promising solution for the remediation of NO pollutants. In this study, the structure–performance correlations of α-, β-, and δ-MnO₂ catalysts were investigated. These three polymorphs of MnO₂ exhibited disparate surface chemistries, NO adsorption capabilities, and NOOR catalytic activities. In a 1.0 M KOH electrolyte, α-MnO₂, characterized by its large-sized (2 × 2) one-dimensional tunnel structure, demonstrated the most outstanding NOOR catalytic performance, which achieved a remarkable NO₃⁻ yield of 665.2 mg·h⁻¹·mg_cat⁻¹ at a potential of 1.9 V, along with excellent stability and durability. Furthermore, a Zn-NO system was constructed, employing α-MnO₂ as the anode and a Zn plate as the cathode. This innovative setup integrated an energy storage system with NO electrochemical capture, yielding a NO₃⁻ production rate of 265.5 mg·h⁻¹·mg_cat⁻¹. The density functional theory calculations confirm the NO adsorption performance and catalytic activity of three different crystal forms of MnO₂. Full article