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23 pages, 3221 KiB  
Article
Drought Modulates Root–Microbe Interactions and Functional Gene Expression in Plateau Wetland Herbaceous Plants
by Yuanyuan Chen, Shishi Feng, Qianmin Liu, Di Kang and Shuzhen Zou
Plants 2025, 14(15), 2413; https://doi.org/10.3390/plants14152413 - 4 Aug 2025
Abstract
In plateau wetlands, the interactions of herbaceous roots with ectorhizosphere soil microorganisms represent an important way to realize their ecological functions. Global change-induced aridification of plateau wetlands has altered long-established functional synergistic relationships between plant roots and ectorhizosphere soil microbes, but we still [...] Read more.
In plateau wetlands, the interactions of herbaceous roots with ectorhizosphere soil microorganisms represent an important way to realize their ecological functions. Global change-induced aridification of plateau wetlands has altered long-established functional synergistic relationships between plant roots and ectorhizosphere soil microbes, but we still know little about this phenomenon. In this context, nine typical wetlands with three different moisture statuses were selected from the eastern Tibetan Plateau in this study to analyze the relationships among herbaceous plant root traits and microbial communities and functions. The results revealed that drought significantly inhibited the accumulation of root biomass and surface area as well as the development of root volumes and diameters. Similarly, drought significantly reduced the diversity of ectorhizosphere soil microbial communities and the relative abundances of key phyla of archaea and bacteria. Redundancy analysis revealed that plant root traits and ectorhizosphere soil microbes were equally regulated by soil physicochemical properties. Functional genes related to carbohydrate metabolism were significantly associated with functional traits related to plant root elongation and nutrient uptake. Functional genes related to carbon and energy metabolism were significantly associated with traits related to plant root support and storage. Key genes such as CS,gltA, and G6PD,zwf help to improve the drought resistance and barrenness resistance of plant roots. This study helps to elucidate the synergistic mechanism of plant and soil microbial functions in plateau wetlands under drought stress, and provides a basis for evolutionary research and conservation of wetland ecosystems in the context of global change. Full article
(This article belongs to the Special Issue Soil-Beneficial Microorganisms and Plant Growth: 2nd Edition)
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27 pages, 11944 KiB  
Article
Heatwave-Induced Thermal Stratification Shaping Microbial-Algal Communities Under Different Climate Scenarios as Revealed by Long-Read Sequencing and Imaging Flow Cytometry
by Ayagoz Meirkhanova, Adina Zhumakhanova, Polina Len, Christian Schoenbach, Eti Ester Levi, Erik Jeppesen, Thomas A. Davidson and Natasha S. Barteneva
Toxins 2025, 17(8), 370; https://doi.org/10.3390/toxins17080370 - 27 Jul 2025
Viewed by 362
Abstract
The effect of periodical heatwaves and related thermal stratification in freshwater aquatic ecosystems has been a hot research issue. A large dataset of samples was generated from samples exposed to temporary thermal stratification in mesocosms mimicking shallow eutrophic freshwater lakes. Temperature regimes were [...] Read more.
The effect of periodical heatwaves and related thermal stratification in freshwater aquatic ecosystems has been a hot research issue. A large dataset of samples was generated from samples exposed to temporary thermal stratification in mesocosms mimicking shallow eutrophic freshwater lakes. Temperature regimes were based on IPCC climate warming scenarios, enabling simulation of future warming conditions. Surface oxygen levels reached 19.37 mg/L, while bottom layers dropped to 0.07 mg/L during stratification. Analysis by FlowCAM revealed dominance of Cyanobacteria under ambient conditions (up to 99.2%), while Cryptophyta (up to 98.9%) and Chlorophyta (up to 99.9%) were predominant in the A2 and A2+50% climate scenarios, respectively. We identified temperature changes and shifts in nutrient concentrations, particularly phosphate, as critical factors in microbial community composition. Furthermore, five distinct Microcystis morphospecies identified by FlowCAM-based analysis were associated with different microbial clusters. The combined use of imaging flow cytometry, which differentiates phytoplankton based on morphological parameters, and nanopore long-read sequencing analysis has shed light into the dynamics of microbial communities associated with different Microcystis morphospecies. In our observations, a peak of algicidal bacteria abundance often coincides with or is followed by a decline in the Cyanobacteria. These findings highlight the importance of species-level classification in the analysis of complex ecosystem interactions and the dynamics of algal blooms in freshwater bodies in response to anthropogenic effects and climate change. Full article
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14 pages, 1410 KiB  
Article
Uptake, Distribution, and Activity of Pluronic F68 Adjuvant in Wheat and Its Endophytic Bacillus Isolate
by Anthony Cartwright, Mohammad Zargaran, Anagha Wankhade, Astrid Jacobson, Joan E. McLean, Anne J. Anderson and David W. Britt
Agrochemicals 2025, 4(3), 12; https://doi.org/10.3390/agrochemicals4030012 - 23 Jul 2025
Viewed by 245
Abstract
Surfactants are widely utilized in agriculture as emulsifying, dispersing, anti-foaming, and wetting agents. In these adjuvant roles, the inherent biological activity of the surfactant is secondary to the active ingredients. Here, the hydrophilic non-ionic surface-active tri-block copolymer Pluronic® F68 is investigated for [...] Read more.
Surfactants are widely utilized in agriculture as emulsifying, dispersing, anti-foaming, and wetting agents. In these adjuvant roles, the inherent biological activity of the surfactant is secondary to the active ingredients. Here, the hydrophilic non-ionic surface-active tri-block copolymer Pluronic® F68 is investigated for direct biological activity in wheat. F68 binds to and inserts into lipid membranes, which may benefit crops under abiotic stress. F68’s interactions with Triticum aestivum (var Juniper) seedlings and a seed-borne Bacillus spp. endophyte are presented. At concentrations below 10 g/L, F68-primed wheat seeds exhibited unchanged emergence. Root-applied fluorescein-F68 (fF68) was internalized in root epidermal cells and concentrated in highly mobile endosomes. The potential benefit of F68 in droughted wheat was examined and contrasted with wheat treated with the osmolyte, glycine betaine (GB). Photosystem II activity of droughted plants dropped significantly below non-droughted controls, and no clear benefit of F68 (or GB) during drought or rehydration was observed. However, F68-treated wheat exhibited increased transpiration values (for watered plants only) and enhanced shoot dry mass (for watered and droughted plants), not observed for GB-treated or untreated plants. The release of seed-borne bacterial endophytes into the spermosphere of germinating seeds was not affected by F68 (for F68-primed seeds as well as F68 applied to roots), and the planktonic growth of a purified Bacillus spp. seed endophyte was not reduced by F68 applied below the critical micelle concentration. These studies demonstrated that F68 entered wheat root cells, concentrated in endosomes involved in transport, significantly promoted shoot growth, and showed no adverse effects to plant-associated bacteria. Full article
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18 pages, 3243 KiB  
Article
Potential Use of Cefiderocol and Nanosilver in Wound Dressings to Control Multidrug-Resistant Gram-Negative Bacteria
by Żaneta Binert-Kusztal, Agata Krakowska, Iwona Skiba-Kurek, Magdalena Luty-Błocho, Anna Kula, Aldona Olechowska-Jarząb, Przemysław Dorożyński and Tomasz Skalski
Molecules 2025, 30(15), 3072; https://doi.org/10.3390/molecules30153072 - 23 Jul 2025
Viewed by 258
Abstract
This study evaluated the antimicrobial efficacy of cefiderocol and various forms of silver (ionic and nanoparticulate) as potential components of wound-dressing reagents against both reference and multidrug-resistant (MDR) Gram-negative bacteria. The anticipated synergistic effect between cefiderocol and nanosilver was not consistently observed; in [...] Read more.
This study evaluated the antimicrobial efficacy of cefiderocol and various forms of silver (ionic and nanoparticulate) as potential components of wound-dressing reagents against both reference and multidrug-resistant (MDR) Gram-negative bacteria. The anticipated synergistic effect between cefiderocol and nanosilver was not consistently observed; in fact, for reference strains, the combination was less effective than cefiderocol alone. However, in MDR and cefiderocol-resistant A. baumannii strains, combining both agents enhanced antibacterial efficacy. Notably, the effectiveness of silver did not increase with concentration, and low or medium nanosilver concentrations were often more effective. Mechanistically, high concentrations of silver may antagonize cefiderocol’s action by inhibiting bacterial surface proteins involved in siderophore-mediated uptake. Generalized linear modeling confirmed that the strain type, silver form, concentration, and their interactions significantly influenced inhibition zones. These findings highlight the importance of agent selection, concentration, and formulation in designing effective antimicrobial wound dressings. They also suggest that further research is needed to optimize such combination therapies for clinical use. Full article
(This article belongs to the Special Issue Applied Chemistry in Europe)
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16 pages, 3231 KiB  
Article
Aptamer-Conjugated Magnetic Nanoparticles Integrated with SERS for Multiplex Salmonella Detection
by Fan Sun, Kun Pang, Keke Yang, Li Zheng, Mengmeng Wang, Yufeng Wang, Qiang Chen, Zihong Ye, Pei Liang and Xiaoping Yu
Biosensors 2025, 15(7), 464; https://doi.org/10.3390/bios15070464 - 19 Jul 2025
Viewed by 494
Abstract
Salmonella is a rapidly spreading and widespread zoonotic infectious disease that poses a serious threat to the safety of both poultry and human lives. Therefore, the timely detection of Salmonella in foods and animals has become an urgent need for food safety. This [...] Read more.
Salmonella is a rapidly spreading and widespread zoonotic infectious disease that poses a serious threat to the safety of both poultry and human lives. Therefore, the timely detection of Salmonella in foods and animals has become an urgent need for food safety. This work describes the construction of an aptamer-based sensor for Salmonella detection, using Fe3O4 magnetic beads and Ag@Au core–shell nanoparticles-embedded 4-mercaptobenzoic acid (4MBA). Leveraging the high affinity between biotin and streptavidin, aptamers were conjugated to Fe3O4 magnetic beads. These beads were then combined with Ag@4MBA@Au nanoparticles functionalized with complementary aptamers through hydrogen bonding and π-π stacking interactions, yielding a SERS-based aptamer sensor with optimized Raman signals from 4MBA. When target bacteria are present, aptamer-conjugated magnetic beads exhibit preferential binding to the bacteria, leading to a decrease in the surface-enhanced Raman scattering (SERS) signal. And it was used for the detection of five different serotypes of Salmonella, respectively, and the results showed that the aptamer sensor exhibited a good linear relationship between the concentration range of 102–108 CFU/mL and LOD is 35.51 CFU/mL. The SERS aptasensor was utilized for the detection of spiked authentic samples with recoveries between 94.0 and 100.4%, which proved the usability of the method and helped to achieve food safety detection. Full article
(This article belongs to the Special Issue Aptamer-Based Sensing: Designs and Applications)
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21 pages, 3177 KiB  
Article
The Physiological and Biochemical Mechanisms Bioprimed by Spermosphere Microorganisms on Ormosia henryi Seeds
by Meng Ge, Xiaoli Wei, Yongming Fan, Yan Wu, Mei Fan and Xueqing Tian
Microorganisms 2025, 13(7), 1598; https://doi.org/10.3390/microorganisms13071598 - 7 Jul 2025
Viewed by 333
Abstract
The hard-seed coat of Ormosia henryi significantly impedes germination efficiency in massive propagation, while conventional physical dormancy-breaking methods often result in compromised seed vigor, asynchronous seedling emergence, and diminished stress tolerance. Seed biopriming, an innovative technique involving the inoculation of beneficial microorganisms onto [...] Read more.
The hard-seed coat of Ormosia henryi significantly impedes germination efficiency in massive propagation, while conventional physical dormancy-breaking methods often result in compromised seed vigor, asynchronous seedling emergence, and diminished stress tolerance. Seed biopriming, an innovative technique involving the inoculation of beneficial microorganisms onto seed surfaces or into germination substrates, enhances germination kinetics and emergence uniformity through microbial metabolic functions and synergistic interactions with seed exudates. Notably, spermosphere-derived functional bacteria isolated from native spermosphere soil demonstrate superior colonization capacity and sustained bioactivity. This investigation employed selective inoculation of these indigenous functional strains to systematically analyze dynamic changes in endogenous phytohormones, enzymatic activities, and storage substances during critical germination phases, thereby elucidating the physiological mechanisms underlying biopriming-enhanced germination. The experimental results demonstrated significant improvements in germination parameters through biopriming. Inoculation with the Bacillus sp. strain achieved a peak germination rate (76.19%), representing a 16.19% increase over the control (p < 0.05). The biopriming treatment effectively improved the seed vigor, broke the impermeability of the seed coat, accelerated the germination speed, and positively regulated physiological indicators, especially amylase activity and the ratio of gibberellic acid to abscisic acid. This study establishes a theoretical framework for microbial chemotaxis and rhizocompetence in seed priming applications while providing an eco-technological solution for overcoming germination constraints in O. henryi cultivation. The optimized biopriming protocol addresses both low germination rates and post-germination growth limitations, providing technical support for the seedling cultivation of O. henryi. Full article
(This article belongs to the Section Plant Microbe Interactions)
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19 pages, 523 KiB  
Review
Usage of Silver Nanoparticles in Orthodontic Bonding Reagents
by Janet Jisoo Lee, Meigan Niu, Zinah Shakir, Geelsu Hwang, Chun-Hsi Chung, Mark S. Wolff, Zhong Zheng and Chenshuang Li
J. Funct. Biomater. 2025, 16(7), 244; https://doi.org/10.3390/jfb16070244 - 3 Jul 2025
Viewed by 564
Abstract
Fixed orthodontic appliances, which are cemented to tooth surfaces, complicate the maintenance of oral hygiene and create a rough surface that is favorable for bacteria attachment. Additionally, the presence of orthodontic appliances may conceive a unique environment that interacts with cariogenic microorganisms, fostering [...] Read more.
Fixed orthodontic appliances, which are cemented to tooth surfaces, complicate the maintenance of oral hygiene and create a rough surface that is favorable for bacteria attachment. Additionally, the presence of orthodontic appliances may conceive a unique environment that interacts with cariogenic microorganisms, fostering a distinct microbial ecosystem compared to that of the patients without orthodontic appliances, thus increasing the vulnerability of tooth surfaces to demineralization and caries formation. Silver (Ag) has shown strong antimicrobial effects and has been extensively investigated in the medical field. Here, we aim to review the antibacterial properties and potential side effects of silver nanoparticles (AgNPs) when incorporated into orthodontic bonding reagents. This valuation could contribute to the development of novel bonding reagents designed to prevent the formation of white spot lesions and caries during orthodontic treatments. Full article
(This article belongs to the Special Issue Dental Biomaterials in Implantology and Orthodontics)
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20 pages, 4816 KiB  
Article
Exploring the Structural Design, Antibacterial Activity, and Molecular Docking of Newly Synthesized Zn(II) Complexes with NNO-Donor Carbazate Ligands
by Claudia C. Gatto, Daniel J. de Siqueira, Eduardo de A. Duarte, Érica C. M. Nascimento, João B. L. Martins, Mariana B. Santiago, Nagela B. S. Silva and Carlos H. G. Martins
Molecules 2025, 30(13), 2822; https://doi.org/10.3390/molecules30132822 - 30 Jun 2025
Viewed by 392
Abstract
The present work reports the synthesis and structural design of three novel Zn(II) complexes [Zn(L1)(CH3COO)(H2O)] (1), [Zn(L2)2] (2), and [Zn(L3)2] (3) with carbazate ligands, 2-acetylpyridine-methylcarbazate (HL1), 2-acetylpyridine-ethylcarbazate [...] Read more.
The present work reports the synthesis and structural design of three novel Zn(II) complexes [Zn(L1)(CH3COO)(H2O)] (1), [Zn(L2)2] (2), and [Zn(L3)2] (3) with carbazate ligands, 2-acetylpyridine-methylcarbazate (HL1), 2-acetylpyridine-ethylcarbazate (HL2), and 2-acetylpyridine-benzylcarbazate (HL3). All compounds were characterized by spectroscopic methods, and the crystal structures of the complexes were elucidated by single-crystal X-ray. Based on the analysis, distorted square pyramid geometry is suggested for complex (1) and an octahedral geometry is suggested for complexes (2) and (3) with the ligands exhibiting an NNO-donor system. The 3D Hirshfeld surface and the 2D fingerprint plot were used to study the non-covalent interactions in the crystal structures. The in vitro antibacterial investigation of the free ligands and their complexes was performed against different strains of periodontopathogen bacteria. The Zn(II) complexes showed more potent antibacterial activity than the free ligand. Molecular docking studies showed the metal complexes as promising candidates for further therapeutic exploration, particularly in targeting the ATP-binding cassette transporter with peptidase domain of the cariogenic bacteria S. mutans (PDB code 5XE9) and the prolyl tripeptidyl aminopeptidase from P. gingivalis anaerobic bacteria (PDB code 2EEP) inhibition. Full article
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16 pages, 1122 KiB  
Article
Effect of r-Human Insulin (Humulin®) and Sugars on Escherichia coli K-12 Biofilm Formation
by Balbina J. Plotkin, Ira Sigar and Monika Konaklieva
Appl. Microbiol. 2025, 5(3), 58; https://doi.org/10.3390/applmicrobiol5030058 - 27 Jun 2025
Viewed by 223
Abstract
E. coli attaches to, and forms biofilms on various surfaces, including latex and polystyrene, contributing to nosocomial spread. E. coli responds to both exogenous and endogenous insulin, which induces behavioral changes. Human insulin, a quorum signal surrogate for microbial insulin, may affect the [...] Read more.
E. coli attaches to, and forms biofilms on various surfaces, including latex and polystyrene, contributing to nosocomial spread. E. coli responds to both exogenous and endogenous insulin, which induces behavioral changes. Human insulin, a quorum signal surrogate for microbial insulin, may affect the ability of E. coli to interact with latex and polystyrene in the presence of various sugars. E. coli ATCC 25923 was grown in peptone (1%) yeast nitrogen base broth to either the logarithmic or stationary growth phase. Adherence to latex was determined using 6 × 6 mm latex squares placed in a suspension of washed cells (103 CFU/mL; 30 min; 37 °C) in buffer containing insulin at 2, 20, and 200 µU/mL (Humulin® R; Lilly) with and without mannose, galactose, fructose, sorbose, arabinose, xylose, lactose, maltose, melibiose, glucose-6-phosphate, glucose-1-phosphate, and glucosamine at concentrations reported to affect behavioral response. Attachment levels to latex were determined by the press plate method. Biofilm levels were measured in a similar fashion but with overnight cultures in flat bottom uncoated polystyrene plates. Controls were media, insulin, sugar, or buffer alone. Glucose served as the positive control. Overall, the stationary phase cells’ adherence to latex was greater, regardless of the test condition, than was measured for the logarithmic phase cells. The effect of insulin on adherence to latex was insulin and sugar concentration dependent. The addition of insulin (200 µU/mL) resulted in a significantly (p < 0.05) increased adherence to latex and biofilm formation on polystyrene compared with sugar alone for 12 of the 13 sugars tested with stationary phase bacteria and 10 of the 13 sugars tested with logarithmic phase bacteria. Adherence in response to sorbose was the only sugar tested that was unaffected by insulin. These findings show that insulin enhances E. coli’s association with materials in common usage in medical environments in a nutrition-dependent manner. Full article
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14 pages, 4338 KiB  
Article
Microbial Corrosion Behavior of L245 Pipeline Steel in the Presence of Iron-Oxidizing Bacteria and Shewanella algae
by Fanghui Zhu, Yiyang Liu, Chunsheng Wu, Kai Li, Yingshuai Hu, Wei Liu, Shuzhen Yu, Mingxing Li, Xiaohuan Dong and Haobo Yu
Microorganisms 2025, 13(7), 1476; https://doi.org/10.3390/microorganisms13071476 - 25 Jun 2025
Viewed by 348
Abstract
Microbiologically influenced corrosion (MIC) poses significant challenges in oilfield water injection environments, leading to substantial socioeconomic losses. L245 steel, a low-alloy steel widely used in oil and gas pipelines due to its excellent mechanical properties and cost-effectiveness, remains highly vulnerable to MIC during [...] Read more.
Microbiologically influenced corrosion (MIC) poses significant challenges in oilfield water injection environments, leading to substantial socioeconomic losses. L245 steel, a low-alloy steel widely used in oil and gas pipelines due to its excellent mechanical properties and cost-effectiveness, remains highly vulnerable to MIC during long-term service. This study uses surface characterization and electrochemical techniques to investigate the corrosion behavior of L245 pipeline steel under short-cycle conditions in a symbiotic environment of iron-oxidizing bacteria (IOB) and Shewanella algae (S. algae). Key findings revealed that localized corrosion of L245 steel was markedly exacerbated under coexisting IOB and S. algae conditions compared to monoculture systems. However, the uniform corrosion rate under symbiosis fell between the rates observed in the individual IOB and S. algae systems. Mechanistically, the enhanced corrosion under symbiotic conditions was attributed to the synergistic electron transfer interaction: IOB exploited electron carriers secreted by S. algae during extracellular electron transfer (EET), which amplified the microbial consortium’s capacity to harvest electrons from the steel substrate. These results emphasize the critical role of interspecies electron exchange in accelerating localized degradation of carbon steel under complex microbial consortia, with implications for developing targeted mitigation strategies in industrial pipelines exposed to similar microbiological environments. Full article
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19 pages, 2419 KiB  
Article
Microbial Community Shifts and Functional Constraints of Dechlorinators in a Legacy Pharmaceutical-Contaminated Soil
by Xinhong Gan, Qian Liu, Xiaolong Liang, Yudong Chen, Yang Xu and Tingting Mu
Soil Syst. 2025, 9(3), 65; https://doi.org/10.3390/soilsystems9030065 - 25 Jun 2025
Viewed by 359
Abstract
Soil microbial communities are essential for the natural attenuation of organic pollutants, yet their ecological responses under long-term contamination remain insufficiently understood. This study examined the bacterial community structure and the abundance of dechlorinating bacteria at a decommissioned pharmaceutical-chemical site in northern Jiangsu [...] Read more.
Soil microbial communities are essential for the natural attenuation of organic pollutants, yet their ecological responses under long-term contamination remain insufficiently understood. This study examined the bacterial community structure and the abundance of dechlorinating bacteria at a decommissioned pharmaceutical-chemical site in northern Jiangsu Province, China, where the primary pollutants were dichloromethane, 1,2-dichloroethane, and toluene. Eighteen soil samples from the surface (0.2 m) and deep (2.2 m) layers were collected using a Geoprobe-7822DT system and analyzed for physicochemical properties and microbial composition via 16S rRNA gene amplicon sequencing. The results showed that the bacterial community composition was significantly shaped by the soil pH, moisture content, pollutant type, and depth. Dechlorinating bacteria were detected at all sites but exhibited low relative abundance, with higher concentrations in the surface soils. Desulfuromonas, Desulfitobacterium, and Desulfovibrio were the dominant dechlorinators, while Dehalococcoides appeared only in the deep soils. A network analysis revealed positive correlations between the dechlorinators and BTEX-degrading and fermentative taxa, indicating potential cooperative interactions in pollutant degradation. However, the low abundance of dechlorinators suggests that the intrinsic bioremediation capacity is limited. These findings provide new insights into microbial ecology under complex organic pollution, and support the need for integrated remediation strategies that enhance microbial functional potential in legacy-contaminated soils. Full article
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14 pages, 3788 KiB  
Article
Identification of Streptococcus pneumoniae Sortase A Inhibitors and the Interactive Mechanism
by Guizhen Wang, Jiahui Lu, Jingyao Wen, Yifan Duan, Hanbing Zhou, Xinli Peng and Zhandong Li
Crystals 2025, 15(7), 594; https://doi.org/10.3390/cryst15070594 - 24 Jun 2025
Viewed by 375
Abstract
Streptococcus pneumoniae (S. pneumoniae) Sortase A (SrtA) anchors virulence proteins to the surface of the cell wall by recognizing and cleaving the LPXTG motif. These toxins help bacteria adhere to and colonize host cells, promote biofilm formation, and trigger host inflammatory [...] Read more.
Streptococcus pneumoniae (S. pneumoniae) Sortase A (SrtA) anchors virulence proteins to the surface of the cell wall by recognizing and cleaving the LPXTG motif. These toxins help bacteria adhere to and colonize host cells, promote biofilm formation, and trigger host inflammatory responses. Therefore, SrtA is an ideal target for the development of new preparations for S. pneumoniae. In this study, we found that phloretin (pht) and phlorizin (phz) exhibited excellent affinities for SrtA based on virtual screening experiments. We analyzed the interactive mechanism between pht, phz, and alnusone (aln, a reported S. pneumoniae SrtA inhibitor) and SrtA based on molecular dynamics simulation experiments. The results showed that these inhibitors bound to the active pocket of SrtA, and the root mean square deviation (RMSD) and distance analyses showed that these compounds and SrtA maintained stable configuration and binding during the assay. The binding free energy analysis showed that both electrostatic forces (ele), van der Waals forces (vdw), and hydrogen bonds (Hbonds) promoted the binding between pht, phz, and SrtA; however, for the binding of aln and SrtA, the vdw force was much stronger than ele, and Hbonds were not found. The binding free energy decomposition showed that HIS141, ILE143, and PHE119 contributed more energy to promote pht and SrtA binding; ARG215, ASP188, and LEU210 contributed more energy to promote phz and SrtA binding; and HIS141, ASP209, and ARG215 contributed more energy to promote aln and SrtA binding. Finally, the transpeptidase activity of SrtA decreased significantly when treated with different concentrations of pht, phz, or aln, which inhibited S. pneumoniae biofilm formation and adhesion to A549 cells without affecting normal bacterial growth. These results suggest that pht, phtz, and aln are potential materials for the development of novel inhibitors against S. pneumoniae infection. Full article
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17 pages, 1610 KiB  
Article
Antimicrobial Action of Essential Oil of Tagetes minuta: Role of the Bacterial Membrane in the Mechanism of Action
by Anahí Bordón, Sergio A. Rodríguez, Douglas Siqueira de Almeida Chaves, Andrea C. Cutró and Axel Hollmann
Antibiotics 2025, 14(7), 632; https://doi.org/10.3390/antibiotics14070632 - 21 Jun 2025
Viewed by 546
Abstract
Background: The rise in multidrug-resistant bacteria has intensified the search for new antibiotics, drawing attention to essential oils (EOs) for their antimicrobial properties. For this reason, this study focuses on the antimicrobial action of the EO obtained from Tagetes minuta and its impact [...] Read more.
Background: The rise in multidrug-resistant bacteria has intensified the search for new antibiotics, drawing attention to essential oils (EOs) for their antimicrobial properties. For this reason, this study focuses on the antimicrobial action of the EO obtained from Tagetes minuta and its impact on bacterial membranes. Methods: The EO was chemically characterized by chromatography–mass spectrometry, and its antimicrobial activity and its effects on surface and bacterial membrane were assessed by using Zeta potential, membrane transition temperature (Tm) determination; and fluorescence spectroscopy with Laurdan and Di-8 ANEPPS. Results: Twenty-seven compounds could be identified, with (E)-Tagetone, (Z)-Ocimenone, and β-pinene as the most abundant. Afterward, the EO was tested against Escherichia coli (MIC and MBC = 17 mg/mL) and Staphylococcus aureus (MIC = 8.5 mg/mL; MBC > 17 mg/mL), showing antimicrobial action in both bacteria, being more effective against E. coli. Mechanistic studies revealed that the EO interacts with bacterial membranes, increasing the Zeta potential by more than 9 mV and enhancing membrane permeability up to 90%. These effects were further confirmed using model lipid membranes, where the EO induced significant changes in membrane properties, including a reduction in dipole potential and transition temperature, suggesting that some EO components could be inserted into the lipid bilayer, disrupting membrane integrity. Conclusions: The EO from T. minuta demonstrates efficient antimicrobial activity by compromising bacterial membrane structure, highlighting its potential as a natural antimicrobial agent. Full article
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21 pages, 7756 KiB  
Article
The Role of Hydroxyl Modification of Peptidoglycan to Reduce the TTX Toxicity via Superior Absorption
by Chang’e Wang, Yi Guo, Lili Zhang, Junjian Miao and Ying Lu
Foods 2025, 14(12), 2145; https://doi.org/10.3390/foods14122145 - 19 Jun 2025
Viewed by 1806
Abstract
The by-products that may contain tetrodotoxin (TTX) produced during the processing of farmed pufferfish have caused food safety risks and environmental pollution. Peptidoglycan (PG) of lactic acid bacteria could adsorb TTX; however, its complex structure and poor solubility limited adsorption efficiency. In this [...] Read more.
The by-products that may contain tetrodotoxin (TTX) produced during the processing of farmed pufferfish have caused food safety risks and environmental pollution. Peptidoglycan (PG) of lactic acid bacteria could adsorb TTX; however, its complex structure and poor solubility limited adsorption efficiency. In this study, hydroxyl modifications of three PGs (A3α, A1γ and A4α) were realized via TEMPO-mediated selective oxidation of the primary hydroxyl group. Compared with PGs, it was found that the carboxyl density of hydroxyl-modified PGs (HM-PGs) increased from 1.66 mmol/g to 3.33 mmol/g and the surface electronegativity increased from −36 mV to −59 mV. The adsorption capacity of HM-PGs to TTX reached 1.48 μg/mg, which was comparable to the adsorption of the conventional adsorbent chitosan for aflatoxin B1 (1.39 μg/mg). Moreover, HM-PGs decreased the toxicity of TTX from strong toxic to nearly non-toxic, with the toxicity reduction rate reached 99.85%. After treatment with HM-PGs, the mouse hippocampus and neuronal cell model confirmed that lower neural injury and sodium channel blocking effects were observed in the residual TTX, whose neurotoxicity was lower. Molecular docking simulation and physicochemical analysis revealed that the adsorption of TTX by HM-PGs was a complex adsorption mode driven by the synergy of physicochemical interaction. There were both physical adsorptions based on electrostatic and hydrophobic interactions and chemical binding with strong hydrogen bonding (1.46 Å) and Mayer bond order (0.1229). This study not only developed a new, efficient and safe tool for TTX removal, but also provided a theoretical basis for the development of biological toxin removal material. Full article
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14 pages, 3662 KiB  
Article
A Study on the Temperature-Dependent Behavior of Small Heat Shock Proteins from Methanogens
by Nina Kurokawa, Mima Ogawa, Rio Midorikawa, Arisa Kanno, Wakaba Naka, Keiichi Noguchi, Ken Morishima, Rintaro Inoue, Masaaki Sugiyama and Masafumi Yohda
Int. J. Mol. Sci. 2025, 26(12), 5748; https://doi.org/10.3390/ijms26125748 - 16 Jun 2025
Viewed by 285
Abstract
Small heat shock proteins (sHsps) are ubiquitous low-molecular-weight chaperones that prevent protein aggregation under cellular stress conditions. In the absence of stress, they assemble into large oligomers. In response to stress, such as elevated temperatures, they undergo conformational changes that expose hydrophobic surfaces, [...] Read more.
Small heat shock proteins (sHsps) are ubiquitous low-molecular-weight chaperones that prevent protein aggregation under cellular stress conditions. In the absence of stress, they assemble into large oligomers. In response to stress, such as elevated temperatures, they undergo conformational changes that expose hydrophobic surfaces, allowing them to interact with denatured proteins. At heat shock temperatures in bacteria, large sHsp oligomers disassemble into smaller oligomeric forms. Methanogens are a diverse group of microorganisms, ranging from thermophilic to psychrophilic and halophilic species. Accordingly, their sHsps exhibit markedly different temperature dependencies based on their optimal growth temperatures. In this study, we characterized sHsps from both hyperthermophilic and mesophilic methanogens to investigate the mechanisms underlying their temperature-dependent behavior. Using analytical ultracentrifugation, we observed the dissociation of sHsps from a mesophilic methanogen into dimers. The dissociation equilibrium of these oligomers was found to be dependent not only on temperature but also on protein concentration. Furthermore, by generating various mutants, we identified the specific amino acid residues responsible for the temperature dependency observed. The C-terminal region containing the IXI/V motif and the α-crystallin domain were found to be the primary determinants of oligomer stability and its temperature dependence. Full article
(This article belongs to the Collection State-of-the-Art Macromolecules in Japan)
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