Search Results (1,159)

The non-medicinal parts of Polygonatum sibiricum (P. sibiricum) and Gentiana scabra (G. scabra) are abundant but underutilized in Liaoning Province, China, creating an environmental burden. Solid-state fermentation (SSF) offers a strategy to enhance their bioactivity, yet triple microbial co-fermentation remains underexplored. This study applied a triple microbiota—featuring Aspergillus niger (A. niger), Bacillus subtilis (B. subtilis), and Saccharomyces cerevisiae (S. cerevisiae)—to ferment the stems and leaves of both plants. Antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was assessed via the Kirby–Bauer test, while Liquid Chromatography–Tandem Mass Spectrometry (LC–MS/MS)-based non-targeted metabolomics identified differential metabolites and enriched pathways. Co-fermentation significantly increased the inhibition zones to 17.4 ± 0.8 mm for E. coli and 17.7 ± 0.3 mm for S. aureus, a 1.8-fold improvement over the unfermented controls (p < 0.001). Among the 2976 metabolites detected, 1236 were differentially expressed, with Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis highlighting activation of aminoacyl-tRNA biosynthesis, ABC transporter, and phenylalanine–tyrosine–tryptophan pathways. Differential abundance analysis indicated that the aminoacyl-tRNA pathway (DA score > 0.9) is critical for antimicrobial peptide synthesis. Phenylalanine derivatives, including 4-hydroxybenzaldehyde, which increased over 430-fold (Log₂ FC = 8.78), contributed to membrane-disruptive antibacterial effects. Mechanistically, A. niger hydrolyzes cellulose to release precursors, B. subtilis synthesizes antimicrobial peptides, and S. cerevisiae enhances metabolite solubility and excretion, collectively boosting antibacterial activity by 80%, suggesting a potent synergistic interaction among the triple microbiota. This cascade mechanism provides a scalable approach for valorizing approximately 55 million tons of traditional Chinese medicine (TCM) waste annually. Full article

Maintaining the balance between the host and commensal microorganisms is essential for skin health. The disruption of this equilibrium (dysbiosis) can contribute to inflammatory and infectious diseases and accelerate skin aging. Dysbiosis also accompanies skin cancers and may influence their progression. Causes of dysbiosis include exogenous factors such as cosmetics, UV radiation, pollution, and diet, as well as endogenous factors like stress, hormonal imbalances, and aging. Standard antibacterial treatments often eliminate beneficial microbes and may exacerbate conditions. Consequently, there is growing interest in alternative strategies—notably natural plant- and animal-derived products—that can modulate the skin microbiome more selectively and gently. This review presents current knowledge on skin microbiome physiology and dysbiosis and discusses natural compounds and microbiome-based therapies (probiotics, prebiotics, postbiotics) that modulate the skin microbiota. Unlike prior reviews, we provide a comparative perspective on emerging compound classes (e.g., peptides, lipids) and integrate the skin–gut axis concept into the framework, highlighting mechanistic insights at molecular and clinical levels. Our synthesis emphasizes distinct modes of action and evidence levels—from in vitro mechanisms to clinical outcomes—and offers guidance for formulation of microbiome-compatible products. Full article

Antibiotic resistance, especially among Gram-negative bacterial strains, places a massive burden on global healthcare systems as resistance development has outpaced antibiotic discovery. Protein–protein interactions, successful in other therapeutic contexts, are emerging as promising, yet underexplored, targets for the development of novel classes of antibacterials. Pathogen-specific protein–protein interactions are attractive targets because they are often structurally and functionally distinct from host proteins and are less likely to elicit rapid resistance. This review summarizes recent developments in targeting protein–protein interactions in Gram-negative bacteria, focusing on the modulation of five critical cellular processes: membrane regulation, replication, transcription, translation, and toxin-antitoxin systems. We highlight the design and discovery of both small-molecule and peptide-based inhibitors. While many identified modulators exhibit potent in vitro activity against their respective targets, achieving effective penetration of the complex Gram-negative cell envelope remains a major challenge. Nevertheless, the diverse and essential nature of these bacteria-specific protein–protein interactions represents an attractive strategy for developing next-generation antimicrobials to combat drug-resistant pathogens. Full article

Background/Objectives: The global rise in antibiotic resistance necessitates the development of novel antimicrobial agents. Antimicrobial peptides (AMPs), key components of innate immunity, are promising candidates. This study aimed to develop novel therapeutic peptides with enhanced properties through the mutagenesis of natural AMPs and high-throughput screening. Methods: We constructed mutant libraries of three broad-spectrum AMPs—melittin, cecropin, and Hm-AMP2—using mutagenesis with partially degenerate oligonucleotides. Libraries were expressed in Escherichia coli, and antimicrobial activity was assessed through bacterial growth kinetics and droplet serial dilution assays. Candidate molecules were identified by DNA sequencing, and the most promising variants were chemically synthesized. Antimicrobial activity was determined by minimal inhibitory concentration (MIC) against E. coli and Bacillus subtilis, while cytotoxicity was evaluated in human Expi293F cells (IC₉₀) viability. The therapeutic index was calculated as the ratio of an AMP’s cytotoxic concentration to its effective antimicrobial concentration. Results: Mutant forms of melittin (MR1P7, MR1P8) showed significantly reduced cytotoxicity while retaining antimicrobial activity. Cecropin mutants exhibited reduced efficacy against E. coli, but variants CR2P2, CR2P7, and CR2P8 gained activity against Gram-positive bacteria. Mutagenesis of Hm-AMP2 generally decreased activity against E. coli, though two variants (A2R1P5 and A2R3P6) showed retained or enhanced efficacy against B. subtilis while maintaining low cytotoxicity. Conclusions: The proposed strategy successfully generated peptides with improved therapeutic profiles, including reduced toxicity or a broader spectrum of antimicrobial activity, despite not improving all parameters. This approach enables the discovery of novel bioactive peptides to combat antibiotic-resistant pathogens. Full article

Background/Objectives: The rapid emergence of antibiotic-resistant oral pathogens has rendered many conventional therapies increasingly ineffective. Antimicrobial peptides (AMPs) have emerged as a promising therapeutic alternative due to their unique mechanisms of action and low propensity for inducing resistance. The delivery of novel therapeutic AMPs against oral cavity bacterial infections requires effective pharmaceutical dosage formulations. This study investigated the potential of two liposomal formulations for the association and delivery of the antimicrobial peptide (AMP) LL17-32 against the dental bacterial pathogen Porphyromonas gingivalis. Methods: Liposomes composed of either negatively charged soya lecithin (SL) or neutrally charged dioleoyl-phosphatidylcholine (DOPC) phospholipids were formulated and characterized based on their hydrodynamic size distribution, ζ-potential, morphology, membrane fluidity, peptide association efficiency, stability and release of peptide in vitro under physiological conditions. The characterization of their biological activity included efficiency of bacterial killing, bacterial adherence, and mammalian cell cytotoxicity using human gingival keratinocyte (TIGK) cells. Results: Both liposomal formulations exhibited spherical morphology with hydrodynamic diameters smaller than ~170 nm and demonstrated good colloidal stability. LL17-32 showed high association efficiency with both liposomal membranes, with no detectable LL17-32 in vitro release. In biological assays, peptide-loaded DOPC liposomes exhibited dose-dependent bactericidal activity against P. gingivalis, whereas SL liposomes significantly attenuated the bactericidal effect of LL17-32. Both formulations displayed reduced cytotoxicity toward human gingival keratinocyte (TIGK) cells versus free peptide. Conclusions: These findings suggest that DOPC liposomes represent a promising delivery system for LL17-32 by adhering to P. gingivalis and exhibiting minimal cytotoxicity to mammalian cells. This study emphasises the critical role of lipid charge in designing AMP delivery systems for antibacterial applications, while it additionally demonstrates the utility of flow cytometry as a quantitative tool to assess liposome–bacteria association. Full article

Collagen peptides derived from animal skins are valuable bioactive ingredients with diverse nutritional and functional properties. This study systematically compared the nutritional value, collagen structure function properties, and bioactivities of collagen peptides from six types of animal skins, including yak skins from different altitudes, Pingliang Red cattle skin, Xinjiang Brown cattle skin, and donkey skin. In terms of nutritional value, low-altitude yak skin contained 34.15 g/100 g protein and 1.78 g/100 g fat, exhibiting superior overall performance compared with other samples. Regarding structure–function relationships, low-altitude yak skin showed the highest emulsifying activity (12.05 m²/g) and foaming capacity (26%), which were attributed to its smaller particle size and higher surface hydrophobicity, whereas mid-altitude yak skin demonstrated greater thermal stability (115.3 °C) and a more compact microstructure. In terms of bioactivity, yak leather contains 23,558 to 25,966 peptides, with relatively high activity of antibacterial peptides and anti-diabetic peptides. Pingliang red cowhide and Xinjiang brown cowhide contain 1515 and 2186 polypeptides, respectively, which have strong antihypertensive activity. The antibacterial effect of donkey skin is more obvious, with a total peptide count of 11,678. Collectively, these findings reveal significant differences in the nutritional and processing-related properties of the six skin types and provide potential evidence for expanding their applications in the field of functional foods. Full article

Mycobacterium avium is an opportunistic pathogen and a leading contributor to nontuberculous mycobacterial infections in immunocompromised individuals. However, treatment duration, antibiotic toxicity, and resistance present challenges in the management of mycobacterium infections, prompting the need for novel treatment. N-acetylcysteine (NAC) has demonstrated potent antimycobacterial activity, while antimicrobial peptides such as the cyclic [R₄W₄] have shown additive effects when combined with first-line antibiotics. This study aimed to investigate the mechanism and efficacy of NAC and [R₄W₄] combination therapy against M. avium. A membrane depolarization assay was used to evaluate the effects of NAC and [R₄W₄] on M. avium cell membrane integrity. Antimycobacterial activity was assessed by treating cultures with varying concentrations of NAC, [R₄W₄], a combination, or a sham treatment. The same regimens were applied to M. avium-infected THP-1-derived macrophages to assess intracellular efficacy. NAC and [R₄W₄] each disrupted the M. avium membrane potential, with enhanced effects in combination. The combination treatment significantly reduced M. avium survival in both the culture and infected macrophages compared with NAC alone and untreated controls. [R₄W₄] and NAC also demonstrated potent antibacterial activity, while the lowest MIC and the combination of [R₄W₄] and NAC displayed additive effects, indicating an improved bacterial inhibition compared to individual treatments. These findings demonstrate the additive activity of NAC and [R₄W₄] against M. avium in vitro and suggest that combining antioxidant compounds with antimicrobial peptides may represent a promising strategy for treating mycobacterial infections. Full article

Ascorbic acid (AA) and its derivatives (EAA), due to their antioxidant properties, may offer potential support in acne therapy. The aim of this study was to evaluate the effect of compound P6—(KK)₂-KWWW-NH₂—in the presence of AA or EAA on the stability and organization of phosphatidylinositol (PI) monolayers. The conducted experiments showed that the monolayers were in the expanded liquid state (37.45–48.35 mN/m) or in the transitional phase between the expanded liquid and condensed states (51.06–56.82 mN/m). Compression and decompression isotherms indicated the highest flexibility for the PI + P6 system, with the compression reversibility coefficient (R_v) ranging from 87.34% to 97.77%, increasing with temperature in successive loops. The surface pressure vs. time dependence after compound injection into the subphase revealed a decrease in monolayer surface pressure followed by stabilization after approximately 300 s for the PI + P6 + AA and PI + P6 + EAA systems. In contrast, for the PI + P6 system at 35 °C, an increase in surface pressure was observed. Full article

Neopyropia (N.) yezoensis is a widely cultivated red alga in East Asia and valued worldwide for its rich bioactive constituents recognized for their health benefits, including polsaccharides, porphyrans, pigments, phenolic compounds, phycobiliproteins, polyunsaturated fatty acids, myosporin-like amino acids, and both synthetic and recombinant peptides. This review summarizes the current knowledge regarding the therapeutic potential of N. yezoensis extracts and their bioactive compounds. Based on in vitro, ex vitro, and in vivo experimental data (including those on Drosophila melanogaster larvae), this review comprehensively discusses its antioxidant, anti-inflammatory, neuroprotective, anti-atopic dermatitis, anti-colitis, anticancer, anti-aging, anti-atrophy, metabolic health-promoting effects, improving renal health, proliferating, anti-osteoarthritic, anti-allergic, antibacterial, and antivirus activities. The prebiotic effect of N. yezoensis porphyran through modulation of the gut microbiota was also investigated. Studies have indicated that protein hydrolysates and peptides derived from N. yezoensis with low molecular weights and aromatic and/or hydrophobic amino acids contribute significantly to these diverse bioactivities. Although N. yezoensis has shown promising bioactivity in preclinical models, validated clinical data in humans are currently lacking. Future research should prioritize the design and implementation of well-controlled human clinical trials to fully explore their therapeutic potential. Full article

Background/Objective: The rise in bacterial resistance necessitates novel therapeutic strategies beyond conventional antibiotics. Antimicrobial peptides represent promising candidates but face challenges such as instability, enzymatic degradation, and host toxicity. To overcome these limitations, conjugation and structural modifications are being explored. This study focuses on designing peptide-based inhibitors of the quorum-sensing (QS) regulator LasR in Pseudomonas aeruginosa, a key mediator of biofilm formation and antibiotic resistance. Methods: Rationally designed tripeptides and dipeptides conjugated with coumarin-3-carboxylic acid and dihydro-3-amino-2-(3H)-furanone were evaluated using molecular docking. The most promising ligand–protein complexes were further analyzed using molecular dynamics (MD) simulations conducted with the CHARMM-GUI and AMBER tools to assess the stability of the ligand–protein complex systems, and the binding affinities were evaluated using Molecular Mechanics–Poisson Boltzmann Surface Area (MM-PBSA) calculations. Pharmacokinetic and toxicity profiles were predicted using ADMETLab 3.0. Selected compounds were synthesized via solid-phase peptide synthesis, structurally confirmed by ¹H NMR and ESI-MS, and tested for antibacterial and antibiofilm activity against P. aeruginosa ATCC 27853. Results: Computational analyses identified several promising inhibitors with stronger binding affinities than the native autoinducer OdDHL. Coumarin conjugates C004 and C006 showed superior docking scores, while MM-PBSA indicated P004 and C004 had the most favorable binding energies. MD simulations confirmed stable ligand–protein complexes. ADMET predictions highlighted C004 and C006 as having excellent pharmacokinetic properties. Experimental assays showed moderate antibacterial activity (MIC 512–1024 µg/mL) and strong antibiofilm inhibition, particularly for C004 (83% inhibition at ½ MIC). Conclusions: The study demonstrates that peptide–coumarin conjugates, especially C004, are promising tools for disrupting QS and biofilm formation in P. aeruginosa. Further optimization and in vivo validation are needed to advance these compounds toward therapeutic application. Full article

Antimicrobial peptides are potential alternatives to conventional antibiotics, primarily due to broad-spectrum activity and low propensity for inducing bacterial resistance. However, their clinical translation faces challenges, including peptide stability and potential mammalian cell toxicity. This study centers on DGL13K, an all D-amino acid peptide, which overcomes proteolytic susceptibility and demonstrates notable stability and broad-spectrum bactericidal activity without inducing de novo bacterial resistance. This work aimed to enhance the therapeutic properties of DGL13K by using targeted modifications to increase antimicrobial potency and decrease toxicity, as determined by hemolysis. DGL13K derivatives were synthesized and tested, involving amino acid substitutions, stereochemical alterations, and N-terminal functionalization with polyethylene glycol (PEG) or myristoylate. While some modifications altered bacterial specificity and reduced hemolytic activity, none of the tested alterations resulted in a substantial overall improvement compared to the parent DGL13K sequence. Furthermore, the antibacterial efficacy of DGL13K and its variants was significantly inhibited in the presence of 50% serum, suggesting limitations for systemic applications. The findings suggest that the DGL13K sequence, derived from an evolutionarily selected protein, is already highly optimized. Given its stability, broad-spectrum efficacy, in vivo activity, low resistance profile, and high safety margin, DGL13K is a promising therapeutic candidate for topical/localized infections. Full article

Background/Objectives: Helicobacter pylori (H. pylori) is a Gram-negative bacterium that colonizes the human stomach and causes various gastrointestinal diseases. Although antibiotic therapy is the most effective method for its eradication, the increasing prevalence of antibiotic resistance has made treatment increasingly challenging in recent years. In this study, the antimicrobial activity, synergistic effects with antibiotics, and mechanisms of action of Bicarinalin, an antimicrobial peptide (AMP) derived from the venom of Tetramorium bicarinatum, were investigated against H. pylori. Methods: To determine the antibacterial activity of Bicarinalin, a well diffusion assay was performed, yielding an inhibition zone of 18.3 mm at a concentration of 32 µg/mL for ATCC strain. MIC₉₉ values were determined by microdilution tests as 4.8 μg/mL for the reference strain. The enhancement of the antimicrobial potential of levofloxacin and clarithromycin when administered together with Bicarinalin has been demonstrated using the well diffusion method. Results: Inhibition zones increased from 14.2 mm to 20 mm for levofloxacin and from 7.3 mm to 16 mm for clarithromycin. This study is the first to identify DNA and protein leakage caused by Bicarinalin in H. pylori. Intracellular protein and DNA leakage were measured, with protein and DNA levels released into the extracellular environment determined as 33.25% and 55.10%, respectively, following Bicarinalin treatment. Furthermore, to investigate its effect on membrane damage, scanning electron microscopy (SEM) was performed, revealing disrupted cell membrane structures, penetration between cells, and severe deterioration of morphological integrity. Conclusions: This study has demonstrated for the first time that, when administered concomitantly, Bicarinalin enhances the antimicrobial activities of levofloxacin and clarithromycin. This highlights its potential as an adjunctive treatment for H. pylori alongside existing drugs. Full article

Antibiotic resistance is a major health problem globally, highlighting the need for alternative antimicrobials that may potentially reduce the emergence of resistance compared to conventional antibiotics. Antimicrobial peptides (AMPs) are promising candidates because of their broad-spectrum activity. In this study, we designed three derivatives (i.e., Analog-1, -2, and -3) of the native peptide, Wuchuanin-A1, for improving their antibacterial activity against Staphylococcus aureus and Escherichia coli. The hypothesis is that the antibacterial activity of these peptides can be improved by increasing their amphipathicity (evaluated using hydrophobic moment analysis), α-helical stability, and membrane binding properties. In this case, the residues of native peptide were mutated to form an amphipathic peptide, referred to here as Analog-1. Then, the N- and C-termini of Analog-1 were capped with acetyl and amide groups, respectively, to produce Analog-2. Finally, the Asp and Arg residues in Analog-2 were mutated to Glu and Lys residues, respectively, in Analog-3. Circular dichroism (CD) spectra in trifluoroethanol (TFE) or methanol (MeOH) showed that Analog-3 has the highest α-helical stability, followed by Analog-2 and Analog-1. Two-dimensional nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations studies indicated that Analog-2 and -3 have a stable continuous α-helical structure. Both Analog-2 and -3 can form dimer or oligomer at higher concentrations. All three analogs can bind to model membranes of Gram-positive and Gram-negative bacteria, with Analog-3 as the best membrane binding affinity through Langmuir monolayer analysis. Both Analog-2 and -3 have better antibacterial activities against S. aureus and E. coli compared to Analog-1 and the native peptide, with minimum inhibitory concentration (MIC) values 3.91 µg/mL against S. aureus and 62.5 µg/mL against E. coli, which are 2–32-fold lower than those of Analog-1. In addition, Analog-2 and -3 have better activity against S. aureus than E. coli bacteria. We proposed that the increase in antibacterial activity of Analog-2 and -3 was due to the α-helical stability, amphipathic structure, and membrane binding properties. Full article

Antimicrobial peptides (AMPs), also referred to as host defense peptides, are promising molecules in the development of the next generation of antibiotics against drug-resistant bacterial pathogens. Thanatin comprises a family of naturally occurring cationic AMPs derived from several species of insects. The first thanatin, 21 residues long, was identified from the spined soldier bug, and more thanatin peptides have been discovered in recent studies. The 16-residue thanatin from Anasa tristis, or Ana-thanatin, represents the shortest sequence in the family. However, the antimicrobial activity and mechanistic process underpinning bacterial cell killing have yet to be reported for Ana-thanatin peptide. In this work, we examined the antibacterial activity, structures, and target interactions of Ana-thanatin. Our results demonstrated that Ana-thanatin exerts potent antibiotic activity against strains of Gram-negative and Gram-positive bacteria. Biophysical studies demonstrated that Ana-thanatin interacts with LPS outer membrane and can permeabilize the OM barrier in the process. Atomic-resolution structures of the peptide in free solution and in complex with lipopolysaccharide (LPS) micelle were solved by NMR, determining canonical β-sheet structures. Notably, in complex with LPS, the β-sheet structure of the peptide was better defined in terms of the packing of amino acid residues. Further, MD simulations demonstrated rapid binding of the Ana-thanatin peptide with the LPS molecules within the lipid bilayers. These studies have revealed structural features which could be responsible for LPS-OM disruption of the Gram-negative bacteria. In addition, NMR heteronuclear single quantum coherence (HSQC) studies have demonstrated that Ana-thanatin can strongly interact with the LPS transport periplasmic protein LptA_m, potentially inhibiting OM biogenesis. Taken together, we surmise that the Ana-thanatin peptide could serve as a template for the further development of novel antibiotics. Full article

Tigecycline is regarded as one of the last-resort antibiotics against multidrug-resistant (MDR) Acinetobacter sp. bacteria. Recently, the tigecycline-resistant Acinetobacter sp. isolates mediated by tet(X) genes have emerged as a class of global pathogens for humans and food-producing animals. However, the genetic diversities and treatment options were not systematically discussed in the era of One Health. In this review, we provide a detailed illustration of the evolution route, distribution characteristics, horizontal transmission, and rapid detection of tet(X) genes in diverse Acinetobacter species. We also detail the application of chemical drugs, plant extracts, phages, antimicrobial peptides (AMPs), and CRISPR-Cas technologies for controlling tet(X)-positive Acinetobacter sp. pathogens. Despite excellent activities, the antibacterial spectrum and application safety need further evaluation and resolution. It is noted that deep learning is a promising approach to identify more potent antimicrobial compounds. Full article