Search Results (1,060)

Treating wastewater with a low carbon-to-nitrogen (C/N) ratio remains a major challenge for conventional biological processes because insufficient organic carbon limits heterotrophic denitrification. To address this issue, microalgae-based photobioreactors offer a sustainable alternative that couples nutrient removal with biomass valorization. This study systematically evaluated the effects of four key operational parameters—initial inoculum density, aeration rate, light intensity, and photoperiod—on nutrient removal, biomass productivity, and metabolite accumulation of Auxenochlorella pyrenoidosa (A. pyrenoidosa) treating synthetic low C/N wastewater. Optimal operating conditions were identified as an initial OD₆₈₀ of 0.1, aeration rate of 2 L air min⁻¹, light intensity of 112 μmol m⁻² s⁻¹, and a 16L:8D photoperiod. Under these conditions, the photobioreactor achieved 86.35% total nitrogen and 98.43% total phosphorus removal within 11 days while producing biomass rich in proteins, polysaccharides, and lipids. Metagenomic analysis revealed a metabolic transition from denitrification-driven pathways during early operation to assimilation-dominated nitrogen metabolism under optimized conditions, emphasizing the synergistic interactions within algal–bacterial consortia. These findings demonstrate that optimized A. pyrenoidosa-based photobioreactors can effectively recover nutrients and produce valuable biomass, offering a viable and sustainable solution for the treatment of low C/N wastewater. Full article

Desertification poses a severe challenge in China. Although long-term sand control measures have proven effective, the extensive and challenging nature of sandy land necessitates systematic research to identify optimal sand control measures for soil amelioration, thereby promoting ecological restoration in sandy areas. This study focused on the Gonghe Basin to assess the effectiveness of four 24-year afforestation treatments—Salix cheilophila + Populus simonii, S. cheilophila, P. simonii (YY), and Caragana korshinskii—compared to untreated mobile dunes. Surface soils (0–10 cm and 10–20 cm) were analyzed for physicochemical properties, enzyme activities, and bacterial community structure using Illumina high-throughput sequencing and PICRUSt2 functional prediction. All afforestation treatments significantly improved soil quality, increasing fine particle content, moisture, nutrients, enzyme activity, and microbial richness and diversity, especially in the topsoil. Bulk density and pH were notably reduced. Among the treatments, YY demonstrated the most substantial improvements. pH emerged as the primary factor influencing bacterial community structure, with enzyme activities also playing a significant role. Metabolism was the dominant functional category across all sites, while YY enhanced environmental information processing functions in the topsoil. Secondary functions showed high redundancy across treatments. These findings confirm that afforestation can effectively rehabilitate degraded alpine sandy soils, with the YY treatment offering the greatest benefits. The study provides a scientific basis for optimizing sand control measures and supports broader ecological restoration efforts in similar environments worldwide. Full article

The emergence of multidrug-resistant Staphylococcus aureus underscores the urgent need for novel therapeutic agents targeting essential bacterial pathways. The lipoteichoic acid synthase (LtaS) is crucial for the synthesis of lipoteichoic acid in the cell wall of Gram-positive bacteria and represents a promising and vulnerable target for antimicrobial drug development. This study employed a comprehensive computational pipeline to identify potent inhibitors of the LtaS enzyme. A library of natural compounds was retrieved from the COCONUT database and screened against the crystal structure of the extracellular domain of LtaS (eLtaS) (PDB ID: 2W5R, obtained from the Protein Data Bank) through a multi-stage molecular docking strategy. This process started with High-Throughput Virtual Screening (HTVS), followed by Standard Precision (SP) docking, and culminated in Extra Precision (XP) docking to refine the selection of hits. The top-ranking compounds from XP docking were subsequently subjected to MM-GBSA binding free energy calculations for further filtration. The stability and dynamic behavior of the resulting candidate complexes were then evaluated using 100 ns molecular dynamics (MD) simulations, which confirmed the structural integrity and binding stability of the ligands. Density Functional Theory calculations revealed that screened ligands exhibit improved electronic stabilization and charge-transfer characteristics compared to a reference compound, suggesting enhanced reactivity and stability relevant for hit identification. Finally, ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) profiling was conducted to assess the drug-likeness and pharmacokinetic safety of the lead compounds. These findings support them as promising orally active leads for further optimization. Our integrated approach shortlisted eight initial hits (A–H) that showed interesting scaffold diversity and finally identified two compounds, herein referred to as Compound A and Compound B, which demonstrated stable binding, favorable free energy, and an acceptable Absorption, Distribution, Metabolism, and Excretion, and Toxicity (ADMET) profile. These candidates emerge as promising starting points for developing novel anti-staphylococcal agents targeting the LtaS enzyme that cand be further proved by experimental validation. Full article

Background: The periodontal pathogen Tannerella forsythia is auxotrophic for muramic acid (MurNAc), a key component of bacterial peptidoglycan, and dependent on an external supply of MurNAc to maintain pure laboratory cultures. The focus of this study was to find a source of muramic acid and peptidoglycan fragments from a Staphylococcus aureus strain. This would facilitate the isolation of T. forsythia by incorporating peptidoglycan into conventional anaerobic media. Methods: The S. aureus strain ATCC 29213 was chosen as the source. The standardization and quantification of the method included verifying concentrations via spectrophotometry and developing a linear regression model with standard curves for muramic acid and lactic acid. The resulting lysate was used to seed Fastidious Anaerobe Agar (FAA) plates, which were inoculated with strain T. forsythia (ATCC 43037) and incubated in an anaerobic chamber for seven days. Results: The resulting lysate had an optical density ranging from 0.061 to 0.083, which corresponds to a muramic acid concentration of approximately 12 µg/mL. Pure cultures of T. forsythia could then be obtained on FAA plates supplemented with muramic acid (MurNAc) (FAA-Mur). The viability of the axenic T. forsythia culture was confirmed using muramic acid/peptidoglycan fragments of microbial origin. Conclusions: The method presented improves the growth of T. forsythia. Consequently, T. forsythia is available for further investigation into the regular performance of sensitivity tests in periodontics and the routine generation of growth curves for quantitative polymerase chain reaction (qPCR) analysis. Full article

Agrobacterium tumefaciens (A. tumefaciens), the causal agent of crown gall disease, is a major threat to crop production worldwide. In this study, a novel lytic bacteriophage, designated P284, was identified and characterized for its antibacterial potential against A. tumefaciens. High-throughput sequencing revealed a 44,922 bp double-stranded DNA genome (G+C content 54.3%), with 66 predicted coding sequences, none associated with virulence, lysogeny, or antibiotic resistance. Genomic and phylogenetic analyses allocated P284 within the genus Atuphduovirus (subfamily Dunnvirinae), showing 94% nucleotide sequence identity and 100% query coverage with phage PAT1, representing a distinct species. Turbidity assays revealed that P284 (MOI = 1) strongly inhibits A. tumefaciens growth up to 48 h, achieving a 92% reduction in bacterial density. Transmission electron microscopy confirmed rapid adsorption and host cell lysis within 30 min. In silico predictions identified three putative depolymerases with properties suitable for recombinant applications. The phage exhibited stability across a wide pH range (3–9) and temperatures from −20 to 60 °C. These findings highlight the lytic activity and environmental resilience of P284, and whether it can control crown gall disease in planta remains to be evaluated. Full article

Sustainable forest management requires a comprehensive understanding of how stand density regulates soil ecological processes. We examined a Larix principis-rupprechtii plantation under three thinning retention densities (High—HD; Medium—MD; Low—LD) and an unthinned control (CK), with soil samples collected from four depth layers (0–10, 10–20, 20–30, and 30–40 cm). This study investigated the effects of stand density on soil properties and microbial communities in a Larix principis-rupprechtii plantation by combining high-throughput sequencing with soil physicochemical analysis to identify the optimal density regime for maintaining soil health. Results demonstrated the following: (1) Moderate-density (MD) management best balanced the stability of soil ecosystem structure, showing superior water retention, organic carbon content, and microbial diversity in the 0–30 cm soil layer. The mechanism underlying these improvements can be attributed to the moderately open canopy structure in MD stands, which facilitated efficient litter decomposition and drove functional complementarity between Basidiomycota (enhancing cellulose degradation capacity) and Acidobacteriota (adapted to oligotrophic conditions). (2) Redundancy analysis revealed that soil pH and available nutrients (AK, AP) were key environmental factors driving microbial community restructuring: Actinobacteriota dominated in neutral, phosphorus-rich environments, while Acidobacteriota thrived under acidic, phosphorus-limited conditions. Fungal communities showed high sensitivity to management intensity, with significant shifts between Ascomycota and Basidiomycota, whereas bacterial communities remained relatively stable due to functional redundancy. We recommend the adoption of moderate-density management as a sustainable practice to enhance soil nutrient cycling and maintain microbial diversity, thereby providing scientific support for sustainable plantation management. Full article

Total joint arthroplasty is among the most common surgical procedures performed worldwide, with frequency increasing due to demographic changes. Accelerating the diagnostic process using new techniques is crucial for effective therapy. This pilot study aims to test such innovative technology in the context of periprosthetic joint infection (PJI) using Scattered Light Integrating Collector (SLIC) technology. While we wish to evaluate whether SLIC can be used to reliably detect the status of infection within human tissue samples in the future, our current research focused on building its foundation by evaluating steps of sample preparation that allow for heightened growth depiction. It is, to our knowledge, the first study concerning the usage of solid human tissue samples using the SLIC device. Adult patients presenting with native or periprosthetic joint infections were included in this prospective study. Biopsies were obtained using sequential sampling, and bacterial density was optimized through titration series. Cryopreservation and agents influencing coagulation were investigated. Our study demonstrates that simple pretreatment could aid in detecting pathogen growth in infected tissue samples. Findings showed a clear advantage for no addition of agents affecting coagulation. Additionally, our protocols proved reliable after prolonged cryopreservation at −20 °C for up to 8 weeks, showing no significant difference compared to primary testing. AUC comparison showed comparable results for sample storage at −80 °C for up to 8 weeks. Similar outcomes were seen for samples ranging from 25 µL to 300 µL, with biological replicates displaying higher thresholds for larger volumes without significant differences. This study introduces a simple and quick diagnostic tool for detecting bacterial growth using tissue biopsies and develops an SOP for further research with this innovative technique. The suggested SOP enables SLIC to hint at an underlying bacterial infection within 5 h using joint tissue, offering a possible novel approach in diagnosing periprosthetic joint infections and septic arthritis. While not yet designed to compare sensitivity to other culture methods, it provides a solid basis for further clinical research. Full article

The influence of light on nutrient removal in microalgae–bacteria biofilm systems containing polyphosphate-accumulating organisms (PAOs) remains unclear under low-carbon-to-nitrogen (C/N) ratio wastewater. This study investigated the effects of different light energy density (Es, 16.23–1101.61 J/gVSS) on the system performance and microbial community of a phototrophic simultaneous nitrification–denitrification phosphorus removal biofilm (P-SNDPRB) system treating wastewater with C/N ratios of 3.19–3.92. At Es below 367.22 J/gVSS, denitrification was the main nitrogen removal pathway, exceeding 82% total nitrogen removal. With increasing Es, nitrogen assimilation increased, while total nitrogen removal declined, remaining above 65%. Phosphorus removal was dependent on phosphorus-accumulating metabolism, achieving exceeding 90% phosphorus removal at Es below 367.22 J/gVSS. However, effluent phosphorus concentrations exceeded 0.5 mg/L at higher Es due to elevated glycogen-accumulating organism (GAO) activity and photoinhibition. Excessive light induced reactive oxygen species accumulation, inhibiting cellular activity and causing bacterial death in flocs. In contrast, the biofilm mitigated light stress, preserving the activity of PAOs, GAOs, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria across different Es levels. These findings demonstrate that P-SNDPRB systems exhibit resilience to fluctuating light conditions, enabling effective nutrient removal in low-C/N wastewater and offering insights into optimizing light management for microalgae-assisted treatment processes. Full article

Conventional chemical-based control methods for soil-borne diseases often degrade soil quality. The recycling of organic wastes offers a promising solution to simultaneously alleviate environmental pollution and restore soil health. As a beneficial fungus, Trichoderma plays a crucial role in enhancing plant performance. However, knowledge of the mechanisms through which organic wastes and Trichoderma interact to influence plant performance remains limited. We investigated how the combined application of organic wastes (chitin and straw) and a biocontrol fungus (Trichoderma) influenced the rhizosphere microbiome to improve plant performance. Compared with the control, organic waste alone, and Trichoderma alone treatments, the combined application of organic wastes and Trichoderma significantly (p < 0.05) increased cucumber yield and reduced pathogen density. Increased yield and reduced pathogen density were associated with changes in bacterial and fungal communities induced by this combined application treatment. Indeed, this combined application treatment enabled plants to recruit certain potentially beneficial core bacterial (e.g., Streptomyces and Flavisolibacter) and fungal taxa (e.g., Trichoderma), increasing their positive interactions in the rhizosphere. We demonstrate that the combined application of organic wastes and Trichoderma can shape distinct rhizosphere bacterial and fungal communities, promoting an increase in beneficial microorganisms and their positive interactions, which contribute to enhanced plant performance. Full article

More than a century ago, bacteriophages (phages) were discovered as entities that could both replicate and dramatically reduce bacterial culture turbidities. By the late 1940s, phage impact on broth turbidity was being studied using electronic detectors. This review examines such turbidimetric, also known as colorimetric or optical density means of studying phage biology. The focus is especially on relatively rapid and higher throughput phenotypic phage characterization versus methods that rely instead on phage plaques, spots, or genotype determinations. Topics covered include (i) the most probable number method along with Appelmans’ approach, (ii) estimation of phage growth parameters including especially that of phage lysis timing, (iii) consideration of lysis inhibition as a complicating factor, (iv) phage titering based on degrees of optical density change, (v) detection of both lysis from without and resistance to lysis from without, (vi) phage host-range determination, and (vii) study of post-lysis culture grow back, that is, of bacterial evolution of phage resistance. Based on over 30 years of experience using and studying optical density approaches to the exploration of broth-culture phage biology, the author takes a critical look at both the benefits and limitations of this increasingly common approach to phage biological characterization. Full article

Urban parks, as vital components of urban green infrastructure, can improve urban ecological environments, showcase urban culture, and offer spaces for human recreation and exercise. However, human activities in these parks also produce severe disruption to soil ecosystems. Studying the effects of recreational disturbances on soil properties and microbial communities is crucial for conserving urban biodiversity and maintaining ecosystem services. This study investigated the effects of human recreational disturbances (HRDs) on soil physicochemical properties and bacterial communities in four forest stands (Phellodendron amurense Rupr (Phe amu), Salix matsudana Koidz. (Sal mat), Pinus tabuliformis var. mukdensis (Pin tab), and Picea asperata Mast. (Pie asp)) in Changchun’s South Lake Park. The results showed that HRD significantly reduced soil water content (SWC) and total phosphorus (TP) while increasing soil bulk density (SBD) and pH. Soil organic carbon (SOC) and total nitrogen (TN) increased in Phe amu and Pie asp soils but decreased in Sal mat and Pin tab soils (p < 0.05). Electrical conductivity (EC) changes were inversely related to SOC and TN trends. Dominant bacterial phyla included Actinobacteriota, Proteobacteria, Acidobacteriota, and Chloroflexi. HRD reduced bacterial species richness and diversity by 5.3% and 7.6%, respectively. SWC and SBD were key factors influencing bacterial community dynamics, with SBD affecting Bacteroidota, Proteobacteria, and Myxococcota, and SWC impacting Proteobacteria, Bacteroidota, and Actinobacteriota. These findings provide insights for urban park management, supporting soil microbial diversity and sustainable urban ecosystem development. Full article

Background and Objectives: Upper respiratory tract infections are one of the most common reasons for outpatient admission. Acute pharyngitis is typically caused by viruses and is self-limiting but in up to 30% of cases, secondary bacterial infection may occur, requiring antibacterial treatment. In the face of growing antibacterial resistance due to inappropriate systemic antibiotic use, different topical therapy would have benefits. The objective of this study was to compare changes in throat and tonsillar mucous membrane bacterial density in patients with acute pharyngitis after a single exposure to a local antibacterial agent presented in different pharmaceutical forms—medicated lozenge, throat spray, or a solution for gargling. Materials and Methods: This was a non-interventional observational study that involved 90 adult outpatients with acute pharyngitis. Patients were prescribed to one of three options: medicated lozenges (containing dequalinium chloride and cinchocaine hydrochloride)—Treatment A; throat spray (containing streptocide soluble and norsulfazol-sodium)—Treatment B; or a powder, Furasol^® 100 mg (containing furagin soluble), for use as an external gargling solution—Treatment C. Throat swab culture was collected before and 20 min after the single exposure to the medication. Microbial testing was performed using a semi-quantitative quadrant streak plate method to assess bacterial density before and after exposure. Results: Four pathogenic agents were isolated from the swabs, with Staphylococcus aureus being the most prevalent. Overall, a reduction in post-exposure bacterial growth intensity was observed in 84.6% of the samples after Treatment C exposure, with a statistically significant difference from both Treatment B (57.1%, p < 0.05) and Treatment A (10%, p < 0.05). The difference was also significant between Treatment A and Treatment B. Conclusions: The findings showed that the throat gargling solution had more impact on mucous bacterial load compared to the throat spray and medicated lozenges in the patients with acute pharyngitis. Further research should address the effects of different pharmaceutical forms of the same antibacterial agent, where available. Full article

Pradofloxacin is a third-generation dual enzyme targeting bactericidal veterinary fluoroquinolone, recently approved for use in cattle for bovine respiratory disease, which is active against Gram-positive/negative, atypical and anaerobic bacteria. We compared in vitro killing by pradofloxacin to that by ceftiofur, danofloxacin, enrofloxacin, florfenicol, marbofloxacin, tildipirosin, tilmicosin and tulathromycin against bovine isolates of Mannheimia haemolytica and Pasteurella multocida over a range of bacterial densities (10⁶–10⁹ cfu/mL). Drug concentrations used in the kill assays included the minimum inhibitory and mutant prevention drug concentrations and maximum serum and maximum tissue drug concentrations. Regardless of bacteria density tested and drug concentration used, pradofloxacin consistently killed as many or more (but not fewer) bacterial cells than any other drug tested against M. haemolytica strains. At the 10⁸–10⁹ cfu/mL densities, pradofloxacin killed 99–99.9%, 100% and 100% of bacterial cells at the MPC, maximum serum and maximum tissue drug concentrations, respectively, following 24 h of drug exposure. Indeed, pradofloxacin killed 99.9–99.99% of cells following 30–60 min of exposure to the maximum serum concentration. Similar trends were seen with killing of P. multocida strains by pradofloxacin. Against high-density bacterial populations, pradofloxacin was rapidly bactericidal and consistently killed more cells than the other agents tested. This manuscript represents the most comprehensive comparative in vitro kill study completed to date. Full article

Populations of Culex pipiens, which is considered a primary vector of West Nile Virus, are not uniformly shaped, and hence, they are difficult to work on, not only because of the complex structure of the species but also due to the possible deformations caused by several factors like temperature, pH, parasite, and bacterial density. Larval density is another crucial factor. This study summarizes the effects of larval density in Cx. pipiens as a model of experimental semi-controlled ecomorphs by two different geometric morphometrics methods. The landmark-based method explains that dimorphism is clearly visualized in both the size and shape of the wings. It also shows that females and males have gradually traceable deformations. When the population reaches a high larval density, which is calculated as approximately 0.5 cm³/individual or, in other words, 1 larva/mL in Cx. pipiens, it can be considered a breaking point, where deformations in shape are observed through all study periods, indicating that it is effected separately and varies independently from the other factors. The wings become smaller in both sexes as the larval density increases. Similar results are obtained by Elliptic Fourier Analysis, which explains the difference in the contour of the wing, regardless of where the landmarks on the veins are located. Full article

Human trampling in urban forest parks has received increasing attention, yet its effects on microbial community assembly remain elusive. This study investigated how trampling influences soil physicochemical properties and microbial communities in Zhuyuwan Scenic Area. Neutral and null community models were used to analyze the effects of trampling on microbial assembly processes. Trampling altered both soil physicochemical properties and microbial diversity. Fungal richness differed significantly between control and light-trampling plots. Soil bulk density (SD) was strongly negatively correlated with other soil physical properties, which were positively intercorrelated. Model analyses showed that light trampling strengthened stochastic processes in bacterial community assembly, whereas heavy trampling reduced this effect. Increasing trampling intensity intensified the influence of stochastic processes on fungal community assembly. Bacterial communities were mainly shaped by heterogeneous selection, while fungal communities were primarily governed by dispersal limitation. These results enhance understanding of how trampling disturbance influences microbial community assembly and provide a theoretical basis for the ecological management and restoration of urban forest parks. Full article