The gut microbiota plays a pivotal role in modulating host physiology and longevity through the production of microbial-derived molecules. Among these, bac

Alterations in the abundance of Bacteroides species are linked to the disruption of the intestinal epithelial barrier and chronic inflammation and has been increasingly recognized as a factor in the development of neurological and neuropsychiatric disorders. Nevertheless, the exact role of Bacteroides species in the gut-brain cross-talk is still largely unexplored. Here, we investigated the immunoregulatory and neuromodulatory potential of two poorly characterized Bacteroides species, including Bacteroides cellulosilyticus and Bacteroides xylanisolvens. The results revealed that both Bacteroides isolates reduced inflammation in Caco-2 intestinal epithelial cells by decreasing the level of IL-8 chemokine and transcription of NF-kB, the two key factors involved in gut inflammation development and barrier disruption. In addition, the Bacteroides strains in the co-culture of Caco-2 cells and phytohemagglutinin-stimulated PBMCs reduced the production of pro-inflammatory cytokines TNF-α and IL-1β, as well as Th1-polarizing IFN-γ cytokine. Finally, in Caenorhabditis elegans, Bacteroides strains differently modulated the expression of the genes implicated in GABA, serotonin and dopamine signaling and synaptic vesicles release pointed to the strain-specific effects of these isolates on neural function. Altogether, these in vitro results show that tested Bacteroides strains may exert anti-inflammatory and neuromodulatory effects, indicating their potential role in microbiota-gut-brain axis.

Microbial biofilm formation, a quorum sensing (QS) phenomenon based on cell-to-cell communication through ligand-receptor interactions, is one of the major causes of nosocomial and chronic infections, foodborne diseases and associated deaths. Its inhibition is therefore considered a promising approach to fight infections. In this context, Cantharellus cibarius, Trametes versicolor, Lentinula edodes and Pleurotus ostreatus, ethno-medicinal and culinary mushrooms, have been investigated as an antibiofilm and anti-QS agents against Pseudomonas aeruginosa. The aim of this study was to identify the most effective solvent system for the extraction of bioactive compounds from medicinal mushrooms with antivirulence activity against P. aeruginosa and to elucidate the potential molecular mechanism. In addition, this work aims to address the urgent need for novel, non-antibiotic strategies to combat multidrug-resistant (MDR) pathogens. Fluorescence microscopy (FM), scanning electron microscopy (SEM) and quantitative real-time PCR were employed to explore the antibiofilm and anti-QS potential of mushroom extracts. Chemical characterization of the extracts was performed using Uv-Vis, FTIR and UHPLC Q-ToF MS, while their toxicity was evaluated in an in vivo model using Caenorhabditis elegans. Hot alkali polysaccharide extracts (APE) were the most effective, as they significantly decreased the mRNA levels of all tested QS, especially genes encoding autoinducer synthases (lasI, rhlI and pqsA), by 2- to 17-fold, as well as virulence factor genes of P. aeruginosa. Furthermore, micrographs (FM and SEM) confirmed that all APEs significantly inhibited adhesion and biofilm formation. FTIR and UV-Vis analyses showed that the extracts consisted mainly of polysaccharides, while UHPLC Q-ToF MS analysis revealed the presence of azelaic acid and vanillylacetone in all extracts. The in silico studies showed that vanillylacetone strongly interferes with various QS receptors (LasR, PqsR and RhlR) and could serve as a competitive inhibitor for the autoinducer molecules and possibly induce conformational changes in proteins. APE has also been found to increase the antibacterial efficacy of antibiotics. In vivo toxicity assays with C. elegans demonstrated their safety (with a survival rate of ≥90 %). The tested mushrooms are promising sources of safe, natural antibiofilm and antivirulence agents, justifying their traditional use in infection control and offering potential for novel anti-infective therapies.

The emergence of multidrug-resistant pathogens has driven the development of novel antimicrobial peptides (AMPs) as therapeutic alternatives. Lactolisterin LBU (LBU) is a bacteriocin with promising activity against Gram-positive bacteria, including Staphylococcus aureus. In this study, we designed and evaluated a panel of amino acid variants of LBU to investigate domain–activity relationships and improve activity. Peptides were commercially synthesized, and their effect was evaluated for minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), hemolytic activity, cytotoxicity, in vivo toxicity, and virulence modulation. AlphaFold3 structural prediction of LBU revealed a four-helix topology with amphipathic and hydrophobic segments. Helical wheel projections identified helices I and IV as amphipathic, suggesting their potential involvement in membrane interaction and activity. Glycine-to-alanine substitutions at helix I markedly increased antimicrobial activity but altered toxicity profiles. In contrast, changes at helix junctions and kinks reduced antimicrobial activity. We also showed differential regulation of virulence genes upon sub-MIC treatment. Overall, rational substitution enabled identification of residues critical for activity and toxicity, providing insights into therapeutic tuning of lactolisterin-based peptides.