Search Results (109)

Allium longistylum is a relatively understudied species whose phytochemical composition and biological activities remain largely unexplored. In this study, the first true leaf (FTL) and the second true leaf (STL) of A. longistylum were compared with respect to phenolic composition, antioxidant capacity, antimicrobial activity, and quorum-sensing (QS) inhibition. Total phenolic content (TPC) and total flavonoid content (TFC) were determined spectrophotometrically, while antioxidant activity was evaluated using ABTS and DPPH radical scavenging assays. Antimicrobial and anti-QS activities were assessed against Staphylococcus aureus, Acinetobacter baumannii, and Chromobacterium violaceum. STL exhibited significantly higher TPC and TFC than FTL, consistent with its stronger radical scavenging activity. Both extracts showed moderate antimicrobial activity and reduced violacein production in C. violaceum, indicating interference with QS. UPLC-Q-Orbitrap-ESI-MS/MS profiling tentatively identified several phenolic acids and flavonoid derivatives. HPLC analysis confirmed the presence of selected phenolic compounds, although several prominent peaks in the chromatograms remained unidentified. Many of the compounds detected by UPLC-Q-Orbitrap-ESI-MS/MS and HPLC have previously been reported to exhibit antioxidant, antimicrobial, and anti-QS activities; their presence may therefore contribute to the bioactivities observed in both extracts. However, their contribution to the observed effects remains speculative and requires further validation through targeted isolation and bioactivity testing. The results suggest that A. longistylum is a promising source of phenolic compounds with antioxidant and antimicrobial properties. Full article

Background/Objectives: Cyanobacteria represent a diverse group of microorganisms capable of synthesizing a broad array of biologically active metabolites. Some of these compounds, believed to contribute to the ecological and evolutionary success of cyanobacteria, are increasingly being investigated for potential biomedical and biotechnological applications. They also hold promise in combating the growing threat of antimicrobial resistance (AMR). This screening study aimed to identify Baltic cyanobacterial strains with the potential to produce antibacterial compounds active against streptococci and mycobacteria, as well as quorum sensing inhibitors. Methods/Results: Extracts from forty-four cyanobacterial strains were tested using a broth microdilution assay. The most pronounced activity was observed for extracts derived from two Pseudanabaenaceae strains (KUCC C3 and C4), two Anabaena spp. strains (CCNP 1405 and CCNP 1406), and Aphanizomenon sp. KUCC C1. Inhibition of quorum sensing was the most frequently detected activity, with 30% of the tested extracts inhibiting violacein production in Chromobacterium violaceum ATCC 12472. Growth inhibition of Gram-positive bacteria was less common: 16% of cyanobacterial strains inhibited Streptococcus pyogenes ATCC 12344, and 11% inhibited Mycobacterium smegmatis ATCC 14468. Bioassay-guided fractionation of Aphanizomenon sp. KUCC C1, followed by LC–MS/MS analysis, revealed the presence of glycerolipids and glycolipids, including diacylglycerols (DAGs) and galactosyldiacylglycerols (MGDGs and DGDGs), as major constituents of fractions exhibiting quorum quenching activity. Conclusions: These findings highlight the potential of Baltic cyanobacteria as a source of natural compounds capable of disrupting bacterial communication and growth, offering prospects for the development of novel antimicrobial and anti-virulence agents. Full article

This study investigated the antibiofilm and anti-quorum-sensing (QS) potential of endophyte extracts isolated from medicinal plants and their validation against Pseudomonas aeruginosa. Endophytes were isolated from the plants using the serial dilution method, and the extracts produced by these endophytes were screened for antimicrobial and biofilm-inhibition activity using assays. The efficient extract was biochemically characterized, followed by validation of its secondary metabolite content. Furthermore, QS-regulatory gene expression levels and microscopy were used to confirm inhibition of biofilm formation. A total of 12 cultures, including 8 bacterial and 4 fungal, were isolated and screened, demonstrating efficient antimicrobial activity (zone of inhibition of 18.8 mm) and 64.3% antibiofilm activity. The efficient endophyte isolated from Paederia foetida was identified as Bacillus xiamenensis MM07 by 16S rRNA gene sequencing. MM07 extract analyses by biochemical and Fourier transform infrared methods revealed the presence of diverse biomolecules. A dose-dependent inhibition was observed, achieving up to 83.5, 60.3, 73.2, 82.7, 83.2, and 15.1 in biofilm formation and exopolysaccharide, violacein, pyocyanin, protease, and alginate production, along with 63.2% swimming ability at 30 µg/mL, respectively. Gas chromatography-mass spectrometry analyses validated the presence of major secondary metabolites, including 3,3-dimethyl-4-methylamino-butan-2-one, 6-amino-2-methyl-, 1-iodo-2-methylundecane, and hexadecanoic acid, with the potential to inhibit biofilm and QS activity. Quantitative real-time polymerase chain reaction of QS regulatory genes (lasI, lasR, rhlI, and rhlR) and microscopy analysis confirmed the anti-QS properties, evidenced by a 40.3% decline in gene expression and biofilm inhibition by MM07 extract. These findings highlight the potential of novel B. xiamenensis MM07 endophyte from P. foetida as a sustainable source of biomolecules for combating biofilm-associated infections. Full article

Volatile organic compounds produced by microbes are increasingly recognized as modulators of microbial interactions and mediators of both intra- and inter-kingdom communication. This study explored the possible ecophysiological roles of nine amides from Streptomyces sp. NP10 in quorum sensing (QS) and biofilm formation in Pseudomonas aeruginosa PAO1. GC-MS profiling, synthesis, spectral validation, and co-injection experiments confirmed compound identities. Notably, N-(3-methyl-2-butenyl)acetamide is reported as a new natural product and N-(2-methylbutyl)acetamide as a new Streptomyces-produced metabolite. At subinhibitory concentrations (250 μg/mL), most of the amides enhanced P. aeruginosa biofilm formation, with N-(2-methylbutyl)acetamide, N-(3-methyl-2-butenyl)acetamide, and 2-phenylacetamide showing the strongest effects. Simultaneously, these compounds suppressed QS by reducing the production of N-acyl homoserine lactones (AHLs) and 2-alkyl-4-quinolones (AHQs). Aliphatic acetamides preferentially inhibited short-chain AHLs, while N-acetyltyramine and 2-phenylacetamide mainly affected quinolone signaling. These opposing effects on QS and biofilm are consistent with the involvement of alternative regulatory circuits. Motility assays showed biofilm stimulation was not correlated with altered swarming or twitching. Cross-species assays revealed limited QS inhibition, with only N-acetyltryptamine reducing violacein production in Chromobacterium violaceum CV026. Most of the amides were non-cytotoxic at 100 μM (10.5–20.2 μg/mL), except for 2-phenylacetamide. Overall, these amides likely serve as microbial signals influencing QS and biofilm formation, offering leads for anti-virulence strategies. Full article

Antimicrobial resistance (AMR) poses a global health threat, which is becoming more challenging due to the involvement of bacterial virulence mechanisms such as quorum sensing (QS) and biofilm formation. These systems regulate pathogenic traits and shield bacteria from conventional therapies. Phytocompounds offer promising antivirulence strategies by disrupting QS and biofilms without exerting selective pressure. In this study, emodin, a natural anthraquinone, was evaluated for its anti-QS and antibiofilm efficacy. Emodin inhibited violacein production by 63.86% in C. violaceum 12472. In P. aeruginosa PAO1, it suppressed pyocyanin (68.04%), pyoverdin (48.79%), exoprotease (58.55%), elastase (43.13%), alginate (74.12%), and rhamnolipids (56.37%). In S. marcescens MTCC 97, emodin reduced prodigiosin (55.94%), exoprotease (48.80%), motility (83.27%), and cell surface hydrophilicity (41.20%). Biofilm formation was inhibited by over 50% in all three bacteria, highlighting emodin’s potential as a broad-spectrum antibiofilm agent. Molecular docking analyses indicated that emodin exhibited affinity towards QS regulatory proteins CviR, LasR, and SmaR, implying a possible competitive interaction at their ligand-binding sites. Subsequent molecular dynamics simulations confirmed these observations by demonstrating structural stability in emodin-bound proteins. The collective insights from in vitro assays and computational studies underscore the potential of emodin in interfering with QS-mediated virulence expression and biofilm development. Such findings support the exploration of non-antibiotic QS inhibitors as therapeutic alternatives for managing bacterial infections and reducing dependence on traditional antimicrobial agents. Full article

Multidrug resistance has also been accompanied by the prolonged use of antibiotics that makes complications in treatment. Biofilm in pathogenic bacteria is the most serious challenge linked with chronic illnesses and also contributes to virulence and drug resistance. Several bacterial pathogens employ the Quorum-sensing (QS) mechanism to coordinate their collective behaviors like bioluminescence, virulence, and biofilm formation. Therefore, agents that inhibit or interfere with bacterial QS and biofilm formation are emerging as a new class of next-generation antibacterial. Recently, nanoparticles have been employed to improve the efficacy of existing antibacterial agents. In the present study, gold nanocrystals were synthesized by using Koelreuteria paniculata (KP) leaf extract. Synthesized nanocrystals were characterized by a face-centered cubic structure of ~20 nm by XRD, FTIR, Zeta sizer, and TEM. Biogenic Gold nanocrystals (BGNCs) exhibited extended QS inhibition in bio-indicator strains Chromobacterium violaceum and Pseudomonas aeruginosa biosensor strains. BGNCs strongly suppressed QS-controlled violacein production in C. violaceum CV026, and elastase, protease, pyocyanin, alginate, and biofilm formation in P. aeruginosa (PA01). In addition, BGNCs notably suppressed the relative expression of PA01 quorum sensing, biofilm-forming, and virulence-regulating genes, as quantified by qRT-PCR. As a result of the broad-spectrum suppression of QS and biofilm by BGNCs, it is anticipated that these nontoxic bioactive nanocrystals can be employed as surface sterilization agents in nosocomial infections. Full article

Background/Objectives: The aim of the present study was to evaluate the antimicrobial, antibiofilm, anti-quorum sensing, and cytotoxic activities of the essential oils extracted from the leaves of Dorystoechas hastata Boiss & Helder. ex Bentham (Lamiaceae) (DHL-EO) as well as to determine the chemical composition of the essential oils obtained from both the leaves and roots. Methods: The essential oils of the root and leaf were extracted by the hydrodistillation method. The chemical composition of the two oils was determined by Gas Chromatography–Mass Spectrometry (GC-MS). The antimicrobial activity of DHL-EO was determined against Gram-positive, Gram-negative bacteria, and various Candida species using the broth microdilution method. Pseudomonas aeruginosa PAO1 and Chromobacterium violaceum ATCC 12472 were used for antibiofilm and anti-quorum sensing activities, respectively. The cytotoxic activity of the DHL-EO was examined by MTT assay. Results: Eucalyptol (21.3%), 2-bornanone (17.0%), and α-pinene (10.3%) were the main compounds of the DHL-EO. The root essential oil (DHR-EO) had trans-ferruginol (19.2%), guaiol (14.1%), and ar-abietatriene (14.0%) as the main components. The DHL-EO displayed weak and moderate antimicrobial activity. The DHL-EO showed moderate antibacterial activity against Staphylococcus aureus ATCC 29213 (methicillin-susceptible, MSSA) and S. aureus ATCC 43300 (methicillin-resistant, MRSA), with a MIC value of 12.5 mg/mL. The DHL-EO exhibited the strongest antifungal activity against Candida parapsilosis RSKK 994, with a MIC value of 0.78 mg/mL. It also demonstrated antifungal activity against C. parapsilosis ATCC 22019 and Candida krusei RSKK 3016, with MIC values of 3.12 mg/mL. The DHL-EO showed antibiofilm activity in a concentration-dependent manner, particularly at higher concentrations, and inhibited violacein production in a dose-dependent manner, with anti-quorum sensing activity. The DHL-EO displayed moderate cytotoxic activity against MCF-7 (IC₅₀: 110.3 μg/mL) and A549 (IC₅₀: 120.4 μg/mL) cell lines. Conclusions: The chemical composition of DHL-EO and DHR-EO showed qualitative and quantitative differences from each other in the present study. The essential oil of the leaves showed moderate cytotoxic and antibacterial activities. Full article

Violacein is a natural pigment with a wide range of biological activities, including antimicrobial, antitumor, and immunostimulatory properties. However, its industrial-scale production is hindered by low yields from microbial fermentation. This study investigated the use of scotta, a low-value by-product of the dairy industry, as an alternative and cost-effective substrate for violacein biosynthesis using Janthinobacterium lividum DSM1522. Different types of scotta, including one derived from lactose-free cheese production, were characterized and tested in flask cultures and a 2 L bioreactor. The results demonstrated that both medium dilution and increased oxygen-transfer coefficient (k_La) significantly enhanced violacein production. In the bioreactor, a final yield of 58.72 mg of violacein for each litre of diluted scotta was achieved. The pigment was then stabilized through a spray-drying process using mannitol as a carrier, resulting in a water-soluble powder that retained antibacterial activity against Bacillus subtilis. The drying process also improved pigment solubility in water, suggesting its potential application in formulations to control Gram-positive bacteria. Overall, this study highlights the potential of scotta as a sustainable fermentation substrate and presents a promising encapsulation approach for violacein stabilization. However, further investigations are needed to optimize the spray-drying process, specifically, to characterize the microgranules and to determine their storage stability. Full article

Molecularly imprinted polymers (MIPs) have emerged as promising materials for selectively targeting biomolecules, including quorum sensing autoinducers that regulate bacterial communication and biofilm formation. In this study, both single-template and dual-template strategies were employed to design and synthesize MIPs capable of capturing autoinducer-2 analogs using (3R,4S)-tetrahydro-3,4-furandiol (T1) or (R/S) 2,2-dimethyl-1,3-dioxolane-4-methanol (T2) as the templates. This approach offers translational potential of a complementary or non-antibiotic strategy to conventional antimicrobial therapies in mitigating biofilm-associated infections. Computational modeling guided the rational selection of functional monomers, predicting favorable interaction energies (ΔE_C up to −135 kcal·mol⁻¹) and optimal hydrogen-bonding patterns to enhance template–polymer affinity. The synthesized MIPs were characterized using spectroscopic and microscopic techniques to confirm imprinting efficiency and structural integrity. The adsorption capacity measurements demonstrated higher adsorption capacity and selectivity of MIPs compared to non-imprinted polymers, with the highest selectivity equal to 3.36 for T1 and 3.14 for T2 on MIPs fabricated from methacrylic acid. Preliminary microbiological evaluations using Chromobacterium violaceum ATCC 12472 reveal that the MIPs prepared from 2-hydroxyethyl methacrylate effectively inhibited violacein production by up to 78.2% at 5.0 mg·mL⁻¹, consistent with quorum sensing interference. These findings highlight the feasibility of employing molecular imprinting to target autoinducer-2 analogs, introducing a novel synthetic strategy for disrupting bacterial communication. This further suggests that molecular imprinting can be leveraged to develop potent quorum-sensing inhibitors, an approach that offers translational potential as an alternative to conventional antimicrobial strategies to mitigate biofilm-associated infections. Full article

Tryptophan is synthesized in microorganisms via a five-step enzymatic pathway originating from chorismate, which is a product of the shikimate pathway. As a biosynthetic precursor to a wide range of high-value compounds such as indole-3-acetic acid, indigo, indirubin, and violacein, this pathway has been a central target for metabolic engineering to enhance microbial production. Anthranilate phosphoribosyltransferase (AnPRT) catalyzes the second step of the pathway by transferring a phosphoribosyl group from PRPP to anthranilate, forming phosphoribosyl anthranilate (PRA). AnPRT, the sole member of class IV phosphoribosyltransferases, adopts a unique fold and functions as a homodimer. While the structural basis of AnPRT activity has been elucidated in several organisms, thermostable variants remain underexplored despite their relevance for high-temperature bioprocessing. In this study, the crystal structure of AnPRT from the thermophilic archaeon Methanocaldococcus jannaschii (MjAnPRT) was determined at a 2.16 Å resolution. The enzyme exhibits a conserved dimeric architecture and key catalytic motifs. Comparative structural analysis with mesophilic and hyper thermophilic homologs revealed that MjAnPRT possesses enhanced local stability in catalytically important regions and strengthened inter-subunit interactions. These features likely contribute to its thermostability and provide a valuable framework for the rational design of robust AnPRTs for industrial and synthetic biology applications. Full article

Microbial pigments are gaining acceptance as a green, sustainable substitute for synthetic food pigments due to growing health issues and their adverse health impacts. This review provides an overview of the potential of microbial pigments as natural food colorants and the advantages of microbial pigments over synthetic pigments. Microbial pigments are a natural source of color with medicinal properties like anticancer, antimicrobial, and antioxidant activity. Important pigments covered are astaxanthin, phycocyanin, prodigiosin, riboflavin, β-carotene, violacein, melanin, and lycopene, and their microbial origins and characteristics. The review also covers commercial production of microbial pigments, i.e., strain development and fermentation processes. Microbial pigments also find extensive applications in food industries, including preservatives for food. Also covered are their pharmacological activity and other applications, such as in the formation of nanoparticles. Finally, the challenges and future directions of microbial pigment production are covered, including the need for cost-effective production, regulatory acceptability, and the potential of genetic engineering and fermentation-based technologies to enhance pigment yield and quality. Full article

The growing threat of antibiotic-resistant Gram-negative bacteria highlights the urgent need for innovative, non-bactericidal therapeutic strategies. Quorum-sensing (QS) inhibition has emerged as a promising approach to attenuate bacterial virulence without exerting selective pressure. This study evaluated the antimicrobial, anti-QS, and antibiofilm properties of aqueous extracts from five medicinal plants native to northeastern Mexico: Gymnosperma glutinosum, Ibervillea sonorae, Larrea tridentata, Olea europaea, and Tecoma stans. Disk diffusion and violacein quantification assays using Chromobacterium violaceum demonstrated significant QS inhibition by G. glutinosum and T. stans, with violacein reductions of 60.02% and 52.72%, respectively, at 40 mg/mL. While L. tridentata and O. europaea exhibited antibacterial activity, I. sonorae showed no growth or pigment inhibition but achieved the highest biofilm disruption (89.89%) against Salmonella typhimurium. UPLC-MS analysis identified chlorogenic acid, kaempferol, and D-(−)-quinic acid as major constituents, compounds previously associated with QS modulation. These findings highlight the potential of traditional Mexican plant species as sources of QS inhibitors and bio-film-disrupting agents, supporting their further development as alternatives to conventional antibiotics. Full article

Extremophilic bacteria from extreme environments, such as the Atacama Desert, Salar de Huasco, and Antarctica, exhibit adaptations to intense UV radiation. In this study, we investigated the genomic and structural mechanisms underlying UV resistance in three bacterial isolates identified as Bacillus velezensis PQ169, Pseudoalteromonas sp. AMH3-8, and Rugamonas violacea T1-13. Through integrative genomic analyses, we identified key genes involved in DNA-repair systems, pigment production, and spore formation. Phylogenetic analyses of aminoacidic sequences of the nucleotide excision repair (NER) system revealed conserved evolutionary patterns, indicating their essential role across diverse bacterial taxa. Structural modeling of photolyases from Pseudoalteromonas sp. AMH3-8 and R. violacea T1-13 provided further insights into protein function and interactions critical for DNA repair and UV resistance. Additionally, the presence of a complete violacein operon in R. violacea T1-13 underscores pigment biosynthesis as a crucial protective mechanism. In B. velezensis PQ169, we identified the complete set of genes responsible for sporulation, suggesting that sporulation may represent a key protective strategy employed by this bacterium in response to environmental stress. Our comprehensive approach underscores the complexity and diversity of microbial adaptations to UV stress, offering potential biotechnological applications and advancing our understanding of microbial resilience in extreme conditions. Full article

The search for probiotics to help limit antibiotic resistance is a major scientific challenge. The exploration of Lactobacillus postbiotics represents a promising approach to prevent pathogen invasion. With this aim, Limosilactobacillus fermentum Lf53, with a broad-spectrum of antagonistic activity, was characterized as a candidate probiotic strain with promising transit tolerance and broad spectrum of activity. A study on growth and postbiotic production in modified MRS broth with different carbohydrates and its vegan variant was carried out. This study presents a comprehensive approach to characterizing the anti-virulence properties of postbiotics derived from Lf53. The promising antibacterial, antibiofilm, and anti-quorum sensing activities of the cell-free supernatants (CFS) were assessed as part of the probiotic’s barrier mechanisms. Biofilm inhibition of P. aeruginosa revealed remarkable suppressive effects exerted by the three tested postbiotics, two of which (nCFS and aCFS) exhibited over 50% inhibition and more than 60% for lysates. The postbiotics’ influence on the production of violacein and pyocyanin pigments of Chromobacterium violaceum and Pseudomonas aeruginosa, which are markers for quorum sensing, highlighted their potential in regulating pathogenic mechanisms. The Lf53 lysates showed the most significant inhibition of violacein production across multiple assays, showing 29.8% reduction. Regarding pyocyanin suppression, the postbiotics also demonstrated strong activity. These are the first reported data on complex postbiotics (metabiotics and parabiotics) demonstrating their potential as anti-virulence agents to help combat pathogens associated with antibiotic-resistant infections. Full article

The development of antimicrobial resistance drives the search for molecules capable of inhibiting bacterial virulence. Fungi of the Basidiomycota phylum constitute an important source of compounds with antimicrobial activity. The present paper describes a new species named Fulvifomes mexicanus sp. nov. based on morphological and phylogenetic analyses. The methanolic extract of basidiome of this fungus inhibited the motility of Pseudomonas aeruginosa ATCC 9027 and the production of violacein by Chromobacterium violaceum CV026. The metabolomic study of the extract by liquid chromatography–high-resolution electrospray ionization mass spectrometry (LC-HRESIMS) and molecular networking analyses revealed the presence of a complex composition of metabolites including hispidin derivatives, terpenoids, phenols, furanones, alkylglycerols, pyrones, and γ-butyrolactones, among others. Overall, this work represents the first chemical and biological study of a new species of Fulvifomes mexicanus as a source of antipathogenic metabolites for the development of novel antimicrobial agents. Full article