Search Results (1,041)

Background: Pseudomonas aeruginosa (P. aeruginosa) is a type of pathogen that takes advantage of opportunities to infect and form biofilm during infection. Inhibiting biofilm formation is a promising approach for the treatment of biofilm-related infections. Methods: Here, Y0-C10-HSL (N-cyclopentyl-n-decanamide) was designed, synthesized, and tested for its effect on biofilm formation, motility, and the Caenorhabditis elegans (C. elegans) survival assay. In addition, the molecular mechanism of Y0-C10-HSL on P. aeruginosa biofilm formation was explored using transcriptome analysis. Results: At a concentration of 200 μmol/L Y0-C10-HSL, biofilm and exopolysaccharides were decreased by 38.5% and 29.3%, respectively; Y0-C10-HSL effectively dispersed the pre-formed biofilm and inhibited the motility ability of P. aeruginosa; and the C. elegans survival assay showed that Y0-C10-HSL was safe and provided protection to C. elegans against P. aeruginosa infection (the survival rates of C. elegans were higher than 74% and increased by 39%, 35.1%, and 47.5%, respectively, when treated with 200 μmol/L Y0-C10-HSL at 24, 48, and 80 h). Transcriptome analysis showed that 585 differentially expressed genes (DEGs) were found after treatment with 200 μmol/L Y0-C10-HSL, including 254 up-regulated DEGs and 331 down-regulated DEGs. The genes involved in the quorum sensing system and biofilm formation were down-regulated. Conclusions: Y0-C10-HSL inhibited the biofilm formation and dispersed the pre-formed biofilm of P. aeruginosa through down-regulated genes related to quorum sensing pathways and biofilm formation. These findings provide a theoretical foundation for the treatment and prevention of antibiotic resistance in clinical and environmental microorganisms such as P. aeruginosa. Full article

Pseudomonas aeruginosa is a metabolically versatile opportunistic pathogen capable of surviving in a range of environments. The major contribution to these abilities relies on virulence factor production, e.g., exotoxins, phenazines, and rhamnolipids, regulated through a hierarchical system of communication, named quorum sensing (QS). QS involves the production, release, and recognition of two classes of diffusible signal molecules: N-acyl-homoserine lactones and alkyl-quinolones. These present a central role during P. aeruginosa infection, regulating bacterial virulence and the modulation of the host immune system. The influence of this arsenal of virulence factors on bacterial–host interaction makes P. aeruginosa a highly potential platform for the development of biopharmaceuticals. Here, we comprehensively reviewed the therapeutical applications of P. aeruginosa virulence factors and quorum sensing signaling molecules on pathological conditions, ranging from infections and inflammation to cancer disease. Full article

The presence of bile acids in the cystic fibrosis patient’s lungs contributes to an increase in the inflammatory response, in the dominance of pathogens, as well as in the decline in lung function, increasing morbidity. The aim of this study is to determine the effects of exposure of Pseudomonas aeruginosa to primary and secondary bile acids on the production of several virulence factors which are involved in its pathogenic power. The presence of bile acids in the bacterial culture medium had no effect on growth up to a concentration of 1 mM. However, a slight decrease in the adhesion index as well as a reduction in the virulence of the bacteria on the HT29 cell line could be observed. In this model, exposure of P. aeruginosa to bile acids showed a significant decrease in the production of LasB and AprA proteases due to the reduction in the expression of their genes. A decrease in pyocyanin production was also observed in relation to the effects of bile acids on the quorum sensing regulators. In order to have an effect on gene expression, it is necessary for bile acids to enter the bacteria. P. aeruginosa harbors two potential homologs of the eukaryotic genes encoding the bile acid transporters NTCP1 and NTCP2 that are expressed in hepatocytes and enterocytes, respectively. By carrying out a comparative BLAST-P between the amino acid sequences of the PAO1 proteins and those of NTCP1 and NTCP2, we identified the products of the PA1650 and PA3264 genes as the unique homologs of the two eukaryotic genes. Exposure of the mutant in the PA1650 gene to chenodeoxycholic acid (CDCA) and lithocholic acid (LCA) showed a less significant effect on pyocyanin production than with the isogenic PAO1 strain. Also, no effect of CDCA on the PA3264 gene mutant was observed. This result indicated that CDCA should enter the bacteria by the transporter produced by this gene. The entry of LCA into bacteria seemed more complex and rather responded to a multifactorial system involving the product of the PA1650 gene but also the products of other genes encoding potential transporters. Full article

For the safe use of microbiome-based solutions in agriculture, the genome sequencing of strains composing the inoculum is mandatory to avoid the spread of virulence and multidrug resistance genes carried by them through horizontal gene transfer to other bacteria in the environment. Moreover, the annotated genomes can enable the design of specific primers to trace the inoculum into the soil and provide insights into the molecular and genetic mechanisms of plant growth promotion and biocontrol activity. In the present work, the genome sequences of some members of beneficial microbial consortia that have previously been tested in greenhouse and field trials as promising biofertilizers for maize, tomato and wheat crops have been determined. Strains belong to well-known plant-growth-promoting bacterial genera such as Bacillus, Burkholderia, Pseudomonas and Rahnella. The genome size of strains ranged from 4.5 to 7.5 Mbp, carrying many genes spanning from 4402 to 6697, and a GC content of 0.04% to 3.3%. The annotation of the genomes revealed the presence of genes that are implicated in functions related to antagonism, pathogenesis and other secondary metabolites possibly involved in plant growth promotion and gene clusters for protection against oxidative damage, confirming the plant-growth-promoting (PGP) activity of selected strains. All the target genomes were found to possess at least 3000 different PGP traits, belonging to the categories of nitrogen acquisition, colonization for plant-derived substrate usage, quorum sensing response for biofilm formation and, to a lesser extent, bacterial fitness and root colonization. No genes putatively involved in pathogenesis were identified. Overall, our study suggests the safe application of selected strains as “plant probiotics” for sustainable agriculture. Full article

Transforming agri-food wastes into valuable products is crucial due to their significant environmental impact, when discarded, including energy consumption, water use, and carbon emissions. This review aims to explore the current research on the recovery of bioactive molecules with antimicrobial properties from agri-food waste and by-products, and discusses future opportunities for promoting a circular economy in its production and processing. Mainly, antibacterial molecules extracted from agri-food wastes are phenolic compounds, essential oils, and saponins. Their extraction and antimicrobial activity against a wide spectrum of bacteria is analyzed in depth. Also, their possible mechanisms of activity are described and classified based on their effect on bacteria, such as the (i) alteration of the cell membrane, (ii) inhibition of energy metabolism and DNA synthesis, and iii) disruption of quorum sensing and biofilm formation. These bioactive molecules have a wide range of possible applications ranging from cosmetics to food packaging. However, despite their potential, the amount of wastes transformed into valuable compounds is very low, due to the high costs relating to their extraction, technical challenges in managing supply chain complexity, limited infrastructure, policy and regulatory barriers, and public perception. For these reasons, further research is needed to develop cost-effective, scalable technologies for biomass valorization. Full article

Xylella fastidiosa is an aerobic, Gram-negative bacterium that is responsible for many plant diseases. The bacterium is the causal agent of Pierce’s disease in grapes and is also responsible for citrus variegated chlorosis, peach phony disease, olive quick decline syndrome and leaf scorches of various species. The production of biofilm is intrinsically linked with persistence and transmission in X. fastidiosa. Biofilm formation is regulated by members of the Diffusible Signal Factor (DSF) quorum sensing signalling family which are comprised of a series of long chain cis-unsaturated fatty acids. This article describes the evaluation of a library of N-acyl sulfonamide bioisosteric analogues of BDSF, XfDSF1 and XfDSF2 for their ability to control biofilm production in X. fastidiosa. The compounds were screened against both the wild-type strain Temecula and an rpfF* mutant which can perceive but not produce XfDSF. Planktonic cell abundance was measured via OD600 while standard crystal violet assays were used to determine biofilm biomass. Several compounds were found to be effective biofilm inhibitors depending on the nature of the sulfonamide substituent. The findings reported here may provide future opportunities for biocontrol of this important plant pathogen. Full article

Staphylococcus aureus, prevalent in hospital and community settings, forms biofilms that are highly resistant to antibiotics and immune responses, complicating treatment and contributing to chronic infections. These challenges underscore the need for novel treatments that target biofilm formation and effectively reduce bacterial virulence. This study investigates the antibiofilm and antimicrobial efficacy of novel halogenated pyrimidine derivatives against S. aureus, focusing on three compounds identified as potent biofilm inhibitors: 2,4-dichloro-5-fluoropyrimidine (24DC5FP), 5-bromo-2,4-dichloro-7H-pyrrolo[2,3-d]pyrimidine (24DC5BPP), and 2,4-dichloro-5-iodo-7H-pyrrolo[2,3-d]pyrimidine (24DC5IPP). The three active compounds are bacteriostatic. In particular, 24DC5FP at 5 µg/mL achieved a 95% reduction in hemolysis with a minimum inhibitory concentration (MIC) of 50 µg/mL. Interestingly, 24DC5FP increased cell size and produced wrinkled colonies. qRT-PCR analysis showed that 24DC5FP suppressed the gene expressions of agrA and RNAIII (quorum sensing regulator and effector), hla (α-hemolysin), nuc1 (nucleases nuc1), and saeR (S. aureus virulence regulator). These findings suggest that extensive halogenation enhances the antibiofilm and antivirulence activities of pyrimidine derivatives, offering a promising strategy for combatting S. aureus infections, including those resistant to conventional treatments. Full article

Biofilms are complex, highly organized structures formed by microorganisms, with functional cell arrangements that allow for intricate communication. Severe clinical challenges occur when anaerobic bacterial species establish long-lasting infections, especially those involving biofilms. These infections can occur in device-related settings (e.g., implants) as well as in non-device-related conditions (e.g., inflammatory bowel disease). Within biofilms, bacterial cells communicate by producing and detecting extracellular signals, particularly through specific small signaling molecules known as autoinducers. These quorum-sensing signals are crucial in all steps of biofilm formation: initial adhesion, maturation, and dispersion, triggering gene expression that coordinates bacterial virulence factors, stimulates immune responses in host tissues, and contributes to antibiotic resistance development. Within anaerobic biofilms, bacteria communicate via quorum-sensing molecules such as N-Acyl homoserine lactones (AHLs), autoinducer-2 (AI-2), and antimicrobial molecules (autoinducing peptides, AIPs). To effectively combat pathogenic biofilms, understanding biofilm formation mechanisms and bacterial interactions is essential. The strategy to disrupt quorum sensing, termed quorum quenching, involves methods like inactivating or enzymatically degrading signaling molecules, competing with signaling molecules for binding sites, or noncompetitively binding to receptors, and blocking signal transduction pathways. In this review, we comprehensively analyzed the fundamental molecular mechanisms of quorum sensing in biofilms formed by anaerobic bacteria. We also highlight quorum quenching as a promising strategy to manage bacterial infections associated with anaerobic bacterial biofilms. Full article

In recent years, plant essential oils have been confirmed as natural inhibitors of foodborne pathogens. Citrus reticulata Blanco cv. Tankan peel essential oil (CPEO) showed anti-Listeria monocytogenes (LM) activities, and this study investigated the associated mechanisms by using high-resolution electron microscope, fluorescence spectrometer, flow cytometer, potentiometer, and transcriptome sequencing. The results showed that CPEO restrained LM growth at a minimum inhibitory concentration of 2% (v/v). The anti-LM abilities of CPEO were achieved by disrupting the permeability of the cell wall, damaging the permeability, fluidity, and integrity of the cell membrane, disturbing the membrane hydrophobic core, and destroying the membrane protein conformation. Moreover, CPEO could significantly inhibit the LM aggregation from forming biofilm by reducing the extracellular polymeric substances’ (protein, polysaccharide, and eDNA) production and bacterial surface charge numbers. The RNA sequencing data indicated that LM genes involved in cell wall and membrane biosynthesis, DNA replication and repair, quorum sensing and two-component systems were expressed differently after CPEO treatment. These results suggested that CPEO could be used as a novel anti-LM agent and green preservative in the food sector. Further studies are needed to verify the anti-LM activities of CPEO in real food. Full article

Biochar has gained interest as a feed ingredient in livestock nutrition due to its functional properties, circularity, potential to reduce environmental impact, and alignment with sustainable agro-zootechnical practices. The in vivo effects of biochar are closely tied to its physical characteristics, which vary depending on the biomass used as feedstock and the production process. This variability can result in heterogeneity among biochar types used in animal nutrition, leading to inconsistent outcomes. The aim of this study was to characterize the metabolomic and functional properties of an aqueous biochar extract from vine pruning waste, in order to predict its potential in vivo effects as a functional feed ingredient. A metabolomic analysis of the biochar extracts was conducted using quadrupole time-f-light (QQTOF) high-performance liquid chromatography tandem mass spectrometry (HPLC MS/MS). Antimicrobial activity against E. coli F18+ and E. coli F4+ was assessed using standard growth inhibition assays, while quorum sensing in E. coli exposed to biochar extracts was evaluated using real-time PCR. Prebiotic activity was assessed by exposing selected Lactobacillus strains to the biochar extract, monitoring growth patterns to determine species-specific responses. The metabolomic profile revealed several distinct molecular classes, including multiple peaks for phenolic compounds. The extract significantly inhibited the growth of both E. coli pathotypes, reducing growth by 29% and 16% for the F4+ and F18+, respectively (p < 0.001). The relative expression of the genes involved in quorum sensing (MotA, FliA for biofilm formation, and FtsE, HflX for cell division) indicated that the observed inhibitory effects likely resulted from interference with flagellar synthesis, motility, and reduced cell division. The biochar extract also showed species-specific prebiotic potential. In conclusion, biochar derived from vine pruning waste represents a valuable feed ingredient with functional properties that may help to reduce antibiotic use in livestock production. Full article

Infective endocarditis (IE) is a life-threatening condition with increasing global incidence, primarily caused by Staphylococcus aureus, especially methicillin-resistant strains (MRSA). Biofilm formation by S. aureus is a critical factor in pathogenesis, contributing to antimicrobial resistance and complicating the treatment of infections involving prosthetic valves and cardiovascular devices. Biofilms provide a protective matrix for MRSA, shielding it from antibiotics and host immune defenses, leading to persistent infections and increased complications, particularly in cases involving prosthetic materials. Clinical manifestations range from acute to chronic presentations, with complications such as heart failure, embolic events, and neurological deficits. Diagnosis relies on the Modified Duke Criteria, which have been updated to incorporate modern cardiovascular interventions and advanced imaging techniques, such as PET/CT (positron emission tomography, computed tomography), to improve the detection of biofilm-associated infections. Management of MRSA-associated IE requires prolonged antimicrobial therapy, often with vancomycin or daptomycin, needing a combination of antimicrobials in the setting of prosthetic materials and frequently necessitates surgical intervention to remove infected prosthetic material or repair damaged heart valves. Anticoagulation remains controversial, with novel therapies like dabigatran showing potential benefits in reducing thrombus formation. Despite progress in treatment, biofilm-associated resistance poses ongoing challenges. Emerging therapeutic strategies, including combination antimicrobial regimens, bacteriophage therapy, antimicrobial peptides (AMPs), quorum sensing inhibitors (QSIs), hyperbaric oxygen therapy, and nanoparticle-based drug delivery systems, offer promising approaches to overcoming biofilm-related resistance and improving patient outcomes. This review provides an overview of the pathogenesis, current management guidelines, and future directions for treating biofilm-related MRSA IE. Full article

Background/Objective: The anti-restriction protein ArdA-H1, found in multiresistant Staphylococcus aureus (MRSA) strains from the ST239-SCCmecIII lineage, inhibits restriction–modification systems, fostering horizontal gene transfer (HGT) and supporting genetic adaptability and resistance. This study investigates the regulatory mechanisms controlling ardA-H1 expression in S. aureus under various stress conditions, including acidic pH, iron limitation, and vancomycin exposure, and explores the roles of the Agr quorum sensing system. Methods: The expression of ardA-H1 was analyzed in S. aureus strains exposed to environmental stressors using real-time quantitative reverse transcription PCR. Comparisons were made between Agr-functional and Agr-deficient strains. In addition, Agr inhibition was achieved using a heterologous Agr autoinducing peptide. Results: The Agr system upregulated ardA-H1 expression in acidic and iron-limited conditions. However, vancomycin induced ardA-H1 activation specifically in the Agr-deficient strain GV69, indicating that an alternative regulatory pathway controls ardA-H1 expression in the absence of agr. The vancomycin response in GV69 suggests that diminished quorum sensing may offer a survival advantage by promoting persistence and HGT-related adaptability. Conclusion: Overall, our findings provide new insights into the intricate relationships between quorum-sensing, stress responses, bacterial virulence, and genetic plasticity, enhancing our understanding of S. aureus adaptability in challenging environments. Full article

Probiotics exhibit significant antivirulence properties that are instrumental in mitigating infectious agents not only within the gastrointestinal tract but also in other parts of the body, including respiratory and urogenital systems. These live microorganisms, beneficial to health when administered in appropriate quantities, operate through several key mechanisms to reduce the pathogenic potential of bacteria, viruses, and fungi. Probiotics effectively reduce colonization and infection severity by enhancing the host’s immune response and directly antagonizing pathogens. One of the major modes of action includes the disruption of quorum sensing pathways, which are essential for bacterial communication and the regulation of virulence factors. Additionally, probiotics compete with pathogens for adhesion sites on host tissues, effectively blocking the establishment and proliferation of infections within a host. This multifaceted interference with pathogen mechanisms highlights the therapeutic potential of probiotics in controlling infectious diseases and enhancing host resilience. This review provides a detailed analysis of these mechanisms, underscoring the potential of probiotics for therapeutic applications to enhance public health. Full article

Background: The emergence and prevalence of antibiotic-resistant bacteria (ARBs) have become a serious global threat, as the morbidity and mortality associated with ARB infections are continuously rising. The activation of quorum sensing (QS) genes can promote biofilm formation, which contributes to the acquisition of drug resistance and increases virulence. Therefore, there is an urgent need to develop new antimicrobial agents to control ARB and prevent further development. Antimicrobial peptides (AMPs) are naturally occurring defense molecules in organisms known to suppress pathogens through a broad range of antimicrobial mechanisms. Methods: In this study, we utilized a previously developed deep-learning model to identify AMP candidates from the venom gland transcriptome of the spider Pardosa astrigera, followed by experimental validation. Results: PA-Win2 was among the top-scoring predicted peptides and was selected based on physiochemical features. Subsequent experimental validation demonstrated that PA-Win2 inhibits the growth of Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and multidrug-resistant P. aeruginosa (MRPA) strain CCARM 2095. The peptide exhibited strong bactericidal activity against P. aeruginosa, and MRPA CCARM 2095 through the depolarization of bacterial cytoplasmic membranes and alteration of gene expression associated with bacterial survival. In addition, PA-Win2 effectively inhibited biofilm formation and degraded pre-formed biofilms of P. aeruginosa. The gene expression study showed that the peptide treatment led to the downregulation of QS genes in the Las, Pqs, and Rhl systems. Conclusions: These findings suggest PA-Win2 as a promising drug candidate against ARB and demonstrate the potential of in silico methods in discovering functional peptides from biological data. Full article

Surfactin, a potent biosurfactant produced by Bacillus subtilis, is synthesized using a non-ribosomal peptide synthetase (NRPS) encoded by the srfAA-AD operon. Despite its association with quorum sensing via the ComX pheromone, the dynamic behavior and in vivo quantification of the NRPS complex remain underexplored. This study established an in vivo quantification system using fluorescence labeling to monitor the availability of surfactin-forming NRPS subunits (SrfAA, SrfAB, SrfAC, and SrfAD) during bioprocesses. Four Bacillus subtilis sensor strains were constructed by fusing these subunits with the megfp gene, resulting in strains BMV25, BMV26, BMV27, and BMV28. These strains displayed growth and surfactin productivity similar to those of the parental strain, BMV9. Fluorescence signals indicated varying NRPS availability, with BMV27 showing the highest and BMV25 showing the lowest relative fluorescence units (RFUs). RFUs were converted to the relative number of NRPS molecules using open-source FPCountR package. During bioprocesses, NRPS availability peaked at the end of the exponential growth phase and declined in the stationary phase, suggesting reduced NRPS productivity under nutrient-limited conditions and potential post-translational regulation. This study provides a quantitative framework for monitoring NRPS dynamics in vivo, offering insights into optimizing surfactin production. The established sensor strains and quantification system enable the real-time monitoring of NRPS availability, aiding bioprocess optimization for industrial applications of surfactin and potentially other non-ribosomal peptides. Full article