Mucosal adjuvanticity and mucosal booster effect of colibactin-depleted probiotic Escherichia coli membrane vesicles

There is a growing interest in development of novel vaccines against respiratory tract infections, due to COVID-19 pandemic. Here, we examined mucosal adjuvanticity and the mucosal booster effect of membrane vesicles (MVs) of a novel probiotic E. coli derivative lacking both flagella and potentially carcinogenic colibactin (ΔflhDΔclbP). ΔflhDΔclbP-derived MVs showed rather strong mucosal adjuvanticity as compared to those of a single flagellar mutant strain (ΔflhD-MVs). In addition, glycoengineered ΔflhDΔclbP-MVs displaying serotype-14 pneumococcal capsular polysaccharide (CPS14+MVs) were well-characterized based on biological and physicochemical parameters. Subcutaneous (SC) and intranasal (IN) booster effects of CPS14+MVs on systemic and mucosal immunity were evaluated in mice that have already been subcutaneously prime-immunized with the same MVs. With a two-dose regimen, an IN boost (SC-IN) elicited stronger IgA responses than homologous prime-boost immunization (SC-SC). With a three-dose regimen, serum IgG levels were comparable among all tested regimens. Homologous immunization (SC-SC-SC) elicited the highest IgM responses among all regimens tested, whereas SC-SC-SC failed to elicit IgA responses in blood and saliva. Furthermore, serum IgA and salivary SIgA levels were increased with an increased number of IN doses administrated. Notably, SC-IN-IN induced not only robust IgG response, but also the highest IgA response in both serum and saliva among the groups. The present findings suggest the potential of a heterologous three-dose administration for building both systemic and mucosal immunity, e.g. an SC-IN-IN vaccine regimen could be beneficial. Another important observation was abundant packaging of colibactin in MVs, suggesting increased applicability of ΔflhDΔclbP-MVs in the context of vaccine safety.

Exploiting membrane vesicles derived from avian pathogenic Escherichia coli as a cross-protective subunit vaccine candidate against avian colibacillosis

Avian pathogenic Escherichia coli (APEC) is a notable pathogen that frequently leads to avian colibacillosis, posing a substantial risk to both the poultry industry and public health. The commercial vaccines against avian colibacillosis are primarily inactivated vaccines, but their effectiveness is limited to specific serotypes. Recent advances have highlighted bacterial membrane vesicles (MV) as a promising candidate in vaccine research. How to produce bacterial MVs vaccines on a large scale is a significant challenge for the industrialization of MVs. The msbB gene encodes an acyltransferase and has been implicated in altering the acylation pattern of lipid A, leading to a decrease in lipid A content in lipopolysaccharides (LPS). Here, we evaluated the immunoprotective efficacy of MVs derived from the LPS low-expressed APEC strain FY26ΔmsbB, which was an APEC mutant strain with a deletion of the msbB gene. The nitrogen cavitation technique was employed to extract APEC MVs, with results indicating a significant increase in MVs yield compared to that obtained under natural culture. The immunization effectiveness was assessed, revealing that FY26ΔmsbB MVs elicited an antibody response of laying hens and facilitated bacterial clearance. Protective efficacy studies demonstrated that immunization with FY26ΔmsbB MVs conferred the immune protection in chickens challenged with the wild-type APEC strain FY26. Notably, LPS low-carried MVs recovered from the mutant FY26ΔmsbB also displayed cross-protective capabilities, and effectively safeguarding against infections caused by O1, O7, O45, O78, and O101 serotypes virulent APEC strains. These findings suggest that MVs generated from the LPS low-expressed APEC strain FY26ΔmsbB represent a novel and empirically validated subunit vaccine for the prevention and control of infections by various APEC serotypes.

Genomic Insights into Disease Resistance in Sunflower (Helianthus annuus): Identifying Key Regions and Candidate Genes for Verticillium dahliae Resistance

Sunflower (Helianthus annuus) is a globally significant field crop, and disease resistance is crucial for ensuring yield stability and crop quality. Verticillium dahliae is a notorious soilborne pathogen that causes Verticillium Wilt (VW) and threatens sunflower production worldwide. In this study, we conducted a comprehensive assessment of sunflower resistance to V. dahliae across 231 sunflower cultivar lines, from the Sunflower Association Mapping (SAM) population. We employed EMMAX and ridge regression best linear unbiased prediction (rrBLUP) and identified 148 quantitative trait loci (QTLs) and 23 putative genes associated with V. dahliae resistance, including receptor like kinases, cell wall modification, transcriptional regulation, plant stress signalling and defense regulation genes. Our enrichment and quantitative real-time PCR validation results highlight the importance of membrane vesicle trafficking in the sunflower immune system for efficient signaling and defense upon activation by V. dahliae. This study also reveals the polygenic architecture of V. dahliae resistance in sunflowers and provides insights for breeding sunflower cultivars resistant to VW. This research contributes to ongoing efforts to enhance crop resilience and reduce yield losses due to VW, ultimately benefiting sunflower growers and the agricultural sector.

Alternatives of mesenchymal stem cell-derived exosomes as potential therapeutic platforms

With outstanding therapeutic potential in the tissue regeneration and anti-inflammation, mesenchymal stem cell-derived exosomes (MSC-EXOs) have emerged as a prominent therapeutic in recent. However, poor production yield and reproducibility have remained as significant challenges of their practical applications. To surmount these challenges, various alternative materials with stem cell-like functions, have been recently investigated, however, there has been no comprehensive analysis in these alternatives so far. Here, we discuss the recent progress of alternatives of MSC-EXOs, including exosomes and exosome-like nanovesicles from various biological sources such as plants, milk, microbes, and body fluids. Moreover, we extensively compare each alternative by summarizing their unique functions and mode of actions to suggest the expected therapeutic target and future directions for developing alternatives for MSC-EXOs.

Alkaline shock protein 23 (Asp23)-controlled cell wall imbalance promotes membrane vesicle biogenesis in Staphylococcus aureus

Membrane vesicles (MVs) are produced by species across all domains of life and have diverse physiological functions as well as promising applications. While the mechanisms for vesiculation in Gram-negative bacteria are well-established, the genetic determinants and regulatory factors responsible for MV biogenesis in Gram-positive bacteria remain largely unknown. Here, we demonstrate that a Q225P substitution in the alternative sigma factor B (SigB) triggers MV production in Staphylococcus aureus strain Newman by hindering the specific binding of SigB to the asp23 promoter, thereby repressing expression of alkaline shock protein 23 (Asp23). Isogenic deletion of asp23 also promotes MV formation in Newman, confirming the critical roles played by sigB and asp23 in modulating S. aureus vesiculation. While bacterial growth and cytoplasmic membrane fluidity are not impaired, mutation of asp23 weakens the cell wall and enhances autolysis, consistent with decreased expression of alpha-type psm and lrgAB that modulate murein hydrolase activity. TEM and proteomic analysis show that Newman and asp23 deletion mutant generate MVs with nearly identical morphology and composition, but virulence-associated factors are significantly enriched in MVs from the asp23 mutant. Overall, this study reveals novel genetic determinants underlying S. aureus vesiculation and advances the understanding of the physiology of MV biogenesis in S. aureus.

Proinflammatory Effect of Membrane Vesicles Derived from Enterococcus faecalis at Neutral and Alkaline pH

INTRODUCTION

The present study explored the proinflammatory impact of Enterococcus faecalis membrane vesicles (MVs) derived from culture medium at pH levels of 7.4 and 9.0.

METHODS

E. faecalis MVs were obtained by centrifugation and purified by size-exclusion chromatography. Proteomic analyses were performed on E. faecalis MVs to investigate their components. THP-1 macrophages were exposed to E. faecalis MVs, and the inflammatory cytokines and proteins were evaluated using enzyme-linked immunosorbent assay and immunoblotting. The inflammatory cytokines in the serum of mice with intraperitoneal injection of E. faecalis MVs were evaluated by enzyme-linked immunosorbent assay, and immunophenotyping of spleen cells was investigated with flow cytometry.

RESULTS

Proteomic analysis revealed 196 proteins in E. faecalis MVs obtained under neutral and alkali conditions; 110 proteins were up-regulated, and 79 proteins were down-regulated by alkaline pH. E. faecalis MVs induced secretion of inflammatory factors interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha in a concentration-dependent manner. Immunoblotting revealed that E. faecalis MVs increased expression of pro-IL-1β, nuclear factor kappa Bp65, and Toll-like receptor 2. In vivo studies demonstrated that E. faecalis MVs significantly promoted secretion of IL-1β in mouse serum, whereas inflammatory cells were activated in the spleen. E. faecalis MVs obtained at a pH of 9.0 showed stronger proinflammatory effects than those obtained under neutral pH.

CONCLUSIONS

E. faecalis produces MVs that carry specific proteins associated with virulence factors, and these MVs can promote inflammation in vitro and in vivo. E. faecalis MVs obtained under alkaline conditions have a stronger proinflammatory effect.

Multiomics-Based Biocargo Components Analysis in Enterococcus faecium Membrane Vesicles

Enterococcus spp. have been shown to have gastrointestinal tract protective functions; our recent results suggest that membrane vesicles (MVs) play an important role in the gastric protection of Enterococcus faecium (E. faecium). The specific function is determined by molecular compositions of MVs. To resolve biocargo components in E. faecium MVs (EfmMVs), MVs were isolated from E. faecium culture. Transcriptomics, label-free quantitative proteomics, and untargeted metabolomics were performed to obtain information about the complexity of ribonucleic acids (RNAs), proteins, and metabolites biocargo they carry, respectively. RNA-sequencing identified a total of 2122 transcripts. The top 20 transcripts accounted for 27.63% of total counts, which, including enzymes, participate in glycolysis, ribosomal proteins, DNA-directed RNA polymerases, protein-synthesizing relative enzymes, molecules associated with protein post-translational processing and transport, and peptidoglycan lyases. Label-free quantitative proteomics analysis identified a total of 711 proteins. The top 20 proteins accounted for 48.02% of all identified proteins, which including ribosomal proteins, enzymes participate in glycolysis, DNA-directed RNA polymerases, protein-synthesizing relative enzymes, peptidoglycan lyases, and autolysin. Untargeted metabolomics analysis identified a total of 519 metabolites. The top 20 metabolites accounted for 79.55% of all identified metabolites, which included amino acids, substrates, or products in the metabolism of amino acids, natural organic acids, products in the metabolism of organic acids, ketone compounds, and two other compounds. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses indicated that the identified biocargo components enriched in metabolism, genetic, and environmental information processing. Overall, we hope that the current exploration of multiple "-omics" analyses of this EfmMVs will provide useful information and further groundwork for future studies on E. faecium application.

In silico and biological analyses of missense variants of the human biliary efflux transporter ABCC2: effects of novel rare missense variants

BACKGROUND AND PURPOSE

The ATP-dependent biliary efflux transporter ABCC2, also known as multidrug resistance protein 2 (MRP2), is essential for the cellular disposition and detoxification of various xenobiotics including drugs as well as endogenous metabolites. Common functionally relevant ABCC2 genetic variants significantly alter drug responses and contribute to side effects. The aim of this study was to determine functional consequences of rare variants identified in subjects with European ancestry using in silico tools and in vitro analyses.

EXPERIMENTAL APPROACH

Targeted next-generation sequencing of the ABCC2 gene was used to identify novel variants in European subjects (n = 143). Twenty-six in silico tools were used to predict functional consequences. For biological validation, transport assays were carried out with membrane vesicles prepared from cell lines overexpressing the newly identified ABCC2 variants and estradiol β-glucuronide and carboxydichlorofluorescein as the substrates.

KEY RESULTS

Three novel rare ABCC2 missense variants were identified (W227R, K402T, V489F). Twenty-five in silico tools predicted W227R as damaging and one as potentially damaging. Prediction of functional consequences was not possible for K402T and V489F and for the common linked variants V1188E/C1515Y. Characterisation in vitro showed increased function of W227R, V489F and V1188E/C1515Y for both substrates, whereas K402T function was only increased for carboxydichlorofluorescein.

CONCLUSION AND IMPLICATIONS

In silico tools were unable to accurately predict the substrate-dependent increase in function of ABCC2 missense variants. In vitro biological studies are required to accurately determine functional activity to avoid misleading consequences for drug therapy.

Growth phase matters: Boosting immunity via Lacticasebacillus-derived membrane vesicles and their interactions with TLR2 pathways

Lipid bi-layered particles known as membrane vesicles (MVs), produced by Gram-positive bacteria are a communication tool throughout the entire bacterial growth. However, the MVs characteristics may vary across all stages of maternal culture growth, leading to inconsistencies in MVs research. This, in turn, hinders their employment as nanocarriers, vaccines and other medical applications. In this study, we aimed to comprehensively characterize MVs derived from Lacticaseibacillus rhamnosus CCM7091 isolated at different growth stages: early exponential (6 h, MV6), late exponential (12 h, MV12) and late stationary phase (48 h, MV48). We observed significant differences in protein content between MV6 and MV48 (data are available via ProteomeXchange with identifier PXD041580), likely contributing to their different immunomodulatory capacities. In vitro analysis demonstrated that MV48 uptake rate by epithelial Caco-2 cells is significantly higher and they stimulate an immune response in murine macrophages RAW 264.7 (elevated production of TNFα, IL-6, IL-10, NO). This correlated with increased expression of lipoteichoic acid (LTA) and enhanced TLR2 signalling in MV48, suggesting that LTA contributes to the immunomodulation. In conclusion, we showed that Lacticaseibacillus rhamnosus CCM7091-derived MVs from the late stationary phase boost the immune response the most effectively, which pre-destines them for therapeutical application as nanocarriers.

Multifunctional Composite Scaffold with Nanosilver, Graphene Oxide, and Macrophage Membrane Vesicles for Sequential Treatment of Infected Bone Defects

The management of infected bone defects poses a significant clinical challenge, and current treatment modalities exhibit various limitations. This study focuses on the development of a multifunctional composite scaffold comprising nanohydroxyapatite/polyethyleneglycol diacrylate matrix, silver nanoparticles, graphene oxide (GO), sodium alginate, and M2-type macrophage membrane vesicles (MVs) to enhance the healing of infected bone defects. The composite scaffold demonstrates several key features: first, it releases sufficient quantities of silver ions to effectively eliminate bacteria; second, the controlled release of MVs leads to a notable increase in M2-type macrophages, thereby significantly mitigating the inflammatory response. Additionally, GO acts synergistically with nanohydroxyapatite to enhance osteoinductive activity, thereby fostering bone regeneration. Through meticulous in vitro and in vivo investigations, the composite scaffold exhibits broad-spectrum antimicrobial effects, robust immunomodulatory capabilities, and enhanced osteoinductive activity. This multifaceted composite scaffold presents a promising approach for the sequential treatment of infected bone defects, addressing the antimicrobial, immunomodulatory, and osteogenic aspects. This study introduces innovative perspectives and offers new and effective treatment alternatives for managing infected bone defects.

Reducing the degree of crosslinking of peptidoglycan in Listeria monocytogenes promoted the secretion of membrane vesicles

Listeria monocytogenes (LM) is a Gram-positive (G+) bacterium that secretes nanoscale membrane vesicles (MVs). LM MVs comprise various bacterial components and may have potential as an antigen or drug-delivery vehicle; however, the low yield of the LM MVs limits related research. G+-bacterial MVs germinate from the bacterial plasma membrane and must pass through a thick crosslinked peptidoglycan layer for release. Herein, we aimed to increase the release of MVs by reducing the degree of crosslinking of peptidoglycan. We knocked out two genes related to the longitudinal crosslinking of peptidoglycan, dal and dat, and supplemented the knocked-out dal gene through plasmid expression to obtain a stably inherited recombinant strain LMΔdd::pCW633. The structure, particle size, and main protein components of MVs secreted by this recombinant strain were consistent with those secreted from the wild strain, but the yield of MVs was considerably increased (p < 0.05). Furthermore, Listeria ivanovii (LI) was found to secrete MVs that differed in the composition of the main proteins compared with those of LM MVs. The abovementioned method was also feasible for promoting the secretion of MVs from the attenuated LM strain and LI wild-type and attenuated strains. Our study provides a new method to increase the secretion of MVs derived from Listeria that could be extended to other G+ bacteria.

Biofilm-derived membrane vesicles exhibit potent immunomodulatory activity in Pseudomonas aeruginosa PAO1

Pathogenic bacteria form biofilms on epithelial cells, and most bacterial biofilms show increased production of membrane vesicles (MVs), also known as outer membrane vesicles in Gram-negative bacteria. Numerous studies have investigated the MVs released under planktonic conditions; however, the impact of MVs released from biofilms on immune responses remains unclear. This study aimed to investigate the characteristics and immunomodulatory activity of MVs obtained from both planktonic and biofilm cultures of Pseudomonas aeruginosa PAO1. The innate immune responses of macrophages to planktonic-derived MVs (p-MVs) and biofilm-derived MVs (b-MVs) were investigated by measuring the mRNA expression of proinflammatory cytokines. Our results showed that b-MVs induced a higher expression of inflammatory cytokines, including Il1b, Il6, and Il12p40, than p-MVs. The mRNA expression levels of Toll-like receptor 4 (Tlr4) differed between the two types of MVs, but not Tlr2. Polymyxin B significantly neutralized b-MV-mediated cytokine induction, suggesting that lipopolysaccharide of native b-MVs is the origin of the immune response. In addition, heat-treated or homogenized b-MVs induced the mRNA expression of cytokines, including Tnfa, Il1b, Il6, and Il12p40. Heat treatment of MVs led to increased expression of Tlr2 but not Tlr4, suggesting that TLR2 ligands play a role in detecting the pathogen-associated molecular patterns in lysed MVs. Taken together, our data indicate that potent immunomodulatory MVs are produced in P. aeruginosa biofilms and that this behavior could be a strategy for the bacteria to infect host cells. Furthermore, our findings would contribute to developing novel vaccines using MVs.

Biofilm and bacterial membrane vesicles: recent advances

INTRODUCTION

Bacterial Membrane Vesicles (MVs) play important roles in cell-to-cell communication and transport of several molecules. Such structures are essential components of Extracellular Polymeric Substances (EPS) biofilm matrix of many bacterial species displaying a structural function and a role in virulence and pathogenesis.

AREAS COVERED

In this review were included original articles from the last ten years by searching the keywords 'biofilm' and 'vesicles' on PUBMED and Scopus databases. The articles available in literature mainly describe a positive correlation between bacterial MVs and biofilms formation. The research on Espacenet and Google Patent databases underlines the available patents related to the application of both biofilm MVs and planktonic MVs in inhibiting biofilm formation.

EXPERT OPINION

This review covers and analyzes recent advances in the study of the relationship between bacterial vesicles and biofilm. The huge number of papers discussing the role of MVs confirms the interest aimed at developing new applications in the medical field. The study of the MVs composition and biogenesis may contribute to the identification of components which could be (i) the target for the development of new drugs inhibiting the biofilm establishment; (ii) candidates for the development of vaccines; (iii) biomarkers for the diagnosis of bacterial infections.

Staphylococcus Aureus Membrane Vesicles Kill Tumor Cells Through a Caspase-1-Dependent Pyroptosis Pathway

Introduction

Nanosized outer membrane vesicles (OMVs) from Gram-negative bacteria have attracted increasing interest because of their antitumor activity. However, the antitumor effects of MVs isolated from Gram-positive bacteria have rarely been investigated.

Methods

MVs of Staphylococcus aureus USA300 were prepared and their antitumor efficacy was evaluated using tumor-bearing mouse models. A gene knock-in assay was performed to generate luciferase Antares2-MVs for bioluminescent detection. Cell counting kit-8 and lactic dehydrogenase release assays were used to detect the toxicity of the MVs against tumor cells in vitro. Active caspase-1 and gasdermin D (GSDMD) levels were determined using Western blot, and the tumor inhibition ability of MVs was determined in B16F10 cells treated with a caspase-1 inhibitor.

Results

The vesicular particles of S. aureus USA300 MVs were 55.23 ± 8.17 nm in diameter, and 5 μg of MVs remarkably inhibited the growth of B16F10 melanoma in C57BL/6 mice and CT26 colon adenocarcinoma in BALB/c mice. The bioluminescent signals correlated well with the concentrations of the engineered Antares2-MVs (R2 = 0.999), and the sensitivity for bioluminescence imaging was 4 × 10-3 μg. Antares2-MVs can directly target tumor tissues in vivo, and 20 μg/mL Antares2-MVs considerably reduced the growth of B16F10 and CT26 tumor cells, but not non-carcinomatous bEnd.3 cells. MV treatment substantially increased the level of active caspase-1, which processes GSDMD to trigger pyroptosis in tumor cells. Blocking caspase-1 activation with VX-765 significantly protected tumor cells from MV killing in vitro and in vivo.

Conclusion

S. aureus MVs can kill tumor cells by activating the pyroptosis pathway, and the induction of pyroptosis in tumor cells is a promising strategy for cancer treatment.

Streptomyces extracellular vesicles are a broad and permissive antimicrobial packaging and delivery system

Streptomyces are the primary source of bioactive specialized metabolites used in research and medicine, including many antimicrobials. These are presumed to be secreted and function as freely soluble compounds. However, increasing evidence suggests that extracellular vesicles are an alternative secretion system. We assessed environmental and lab-adapted Streptomyces (sporulating filamentous actinomycetes) and found frequent production of antimicrobial vesicles. The molecular cargo included actinomycins, anthracyclines, candicidin, and actinorhodin, reflecting both diverse chemical properties and diverse antibacterial and antifungal activity. The levels of packaged antimicrobials correlated with the level of inhibitory activity of the vesicles, and a strain knocked out for the production of anthracyclines produced vesicles that lacked antimicrobial activity. We demonstrated that antimicrobial containing vesicles achieve direct delivery of the cargo to other microbes. Notably, this delivery via membrane fusion occurred to a broad range of microbes, including pathogenic bacteria and yeast. Vesicle encapsulation offers a broad and permissive packaging and delivery system for antimicrobial specialized metabolites, with important implications for ecology and translation.IMPORTANCEExtracellular vesicle encapsulation changes our picture of how antimicrobial metabolites function in the environment and provides an alternative translational approach for the delivery of antimicrobials. We find many Streptomyces strains are capable of releasing antimicrobial vesicles, and at least four distinct classes of compounds can be packaged, suggesting this is widespread in nature. This is a striking departure from the primary paradigm of the secretion and action of specialized metabolites as soluble compounds. Importantly, the vesicles deliver antimicrobial metabolites directly to other microbes via membrane fusion, including pathogenic bacteria and yeast. This suggests future applications in which lipid-encapsulated natural product antibiotics and antifungals could be used to solve some of the most pressing problems in drug resistance.

Bacterial membrane vesicles: orchestrators of interkingdom interactions in microbial communities for environmental adaptation and pathogenic dynamics

Bacterial membrane vesicles (MVs) have attracted increasing attention due to their significant roles in bacterial physiology and pathogenic processes. In this review, we provide an overview of the importance and current research status of MVs in regulating bacterial physiology and pathogenic processes, as well as their crucial roles in environmental adaptation and pathogenic infections. We describe the formation mechanism, composition, structure, and functions of MVs, and discuss the various roles of MVs in bacterial environmental adaptation and pathogenic infections. Additionally, we analyze the limitations and challenges of MV-related research and prospect the potential applications of MVs in environmental adaptation, pathogenic mechanisms, and novel therapeutic strategies. This review emphasizes the significance of understanding and studying MVs for the development of new insights into bacterial environmental adaptation and pathogenic processes. Overall, this review contributes to our understanding of the intricate interplay between bacteria and their environment and provides valuable insights for the development of novel therapeutic strategies targeting bacterial pathogenicity.

Interactions of Gram-Positive Bacterial Membrane Vesicles and Hosts: Updates and Future Directions

Extracellular vesicles (EVs) are lipid bilayers derived from cell membranes, released by both eukaryotic cells and bacteria into the extracellular environment. During production, EVs carry proteins, nucleic acids, and various compounds, which are then released. While Gram-positive bacteria were traditionally thought incapable of producing EVs due to their thick peptidoglycan cell walls, recent studies on membrane vesicles (MVs) in Gram-positive bacteria have revealed their significant role in bacterial physiology and disease progression. This review explores the current understanding of MVs in Gram-positive bacteria, including the characterization of their content and functions, as well as their interactions with host and bacterial cells. It offers a fresh perspective to enhance our comprehension of Gram-positive bacterial EVs.

Effect of Polyphenols on Inflammation Induced by Membrane Vesicles from Staphylococcus aureus

Staphylococcus aureus, a bacterium found on human skin, produces toxins and various virulence factors that can lead to skin infections such as atopic dermatitis. These toxins and virulence factors are carried in membrane vesicles (MVs), composed of the bacterium's own cell membranes, and are expected to reach host target cells in a concentrated form, inducing inflammation. This study investigated the effects of two polyphenols, (-)-epigallocatechin gallate (EGCG) and nobiletin (NOL), on the expression of S. aureus virulence factors and the inflammation induced by MVs. The study found that EGCG alone decreased the production of Staphylococcal Enterotoxin A (SEA), while both EGCG and NOL reduced biofilm formation and the expression of virulence factor-related genes. When S. aureus was cultured in a broth supplemented with these polyphenols, the resulting MVs showed a reduction in SEA content and several cargo proteins. These MVs also exhibited decreased levels of inflammation-related gene expression in immortalized human keratinocytes. These results suggest that EGCG and NOL are expected to inhibit inflammation in the skin by altering the properties of MVs derived from S. aureus.

Gram-Positive Bacterial Membrane-Based Biosensor for Multimodal Investigation of Membrane-Antibiotic Interactions

As membrane-mediated antibiotic resistance continues to evolve in Gram-positive bacteria, the development of new approaches to elucidate the membrane properties involved in antibiotic resistance has become critical. Membrane vesicles (MVs) secreted by the cytoplasmic membrane of Gram-positive bacteria contain native components, preserving lipid and protein diversity, nucleic acids, and sometimes virulence factors. Thus, MV-derived membrane platforms present a great model for Gram-positive bacterial membranes. In this work, we report the development of a planar bacterial cytoplasmic membrane-based biosensor using MVs isolated from the Bacillus subtilis WT strain that can be coated on multiple surface types such as glass, quartz crystals, and polymeric electrodes, fostering the multimodal assessment of drug-membrane interactions. Retention of native membrane components such as lipoteichoic acids, lipids, and proteins is verified. This biosensor replicates known interaction patterns of the antimicrobial compound, daptomycin, with the Gram-positive bacterial membrane, establishing the applicability of this platform for carrying out biophysical characterization of the interactions of membrane-acting antibiotic compounds with the bacterial cytoplasmic membrane. We report changes in membrane viscoelasticity and permeability that correspond to partial membrane disruption when calcium ions are present with daptomycin but not when these ions are chelated. This biomembrane biosensing platform enables an assessment of membrane biophysical characteristics during exposure to antibiotic drug candidates to aid in identifying compounds that target membrane disruption as a mechanism of action.

Exploring membrane vesicles in citrus fruits: a comparative analysis of conventional and organic farming approaches

BACKGROUND

Recently, vesicles derived from plant cell membranes have received attention for their potential use as active biomolecules and nanocarriers, and obtaining them from organic crops may be an interesting option because different farming systems can affect production, plant secondary metabolism and biochemistry of cell membranes. The present study aimed to determine how organic and conventional farming affects the mineral nutrition, gas exchange, CO2 fixation and biochemical composition of lemon fruits, which could have an impact on the different fractions of cell membranes in pulp and juice.

RESULTS

Organic trees had higher intrinsic water use efficiency (WUEi) but conventional trees had higher stomatal conductance (gs) and nitrogen use efficiency (NUtE). Also, organic lemons had significantly higher levels of some micronutrients (Ca, Cu, Fe and Zn). Second, the main differences in the membrane vesicles showed that organic pulp vesicles had a higher antioxidant activity and more oleic acid, whereas both types of vesicles from conventional lemons had more linoleic acid.

CONCLUSION

In conclusion, organic farming did not alter carbon fixation parameters but impacted nitrogen fixation and water uptake, and resulted in higher micronutrient levels in lemons. These mineral nutritional changes could be related to the higher production of membranes that showed suitable morphological traits and a high antioxidant activity, positively correlated with a high amount of oleic acid, which could have stronger cell protection characteristics. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Slightly acidic electrolyzed water inhibits inflammation induced by membrane vesicles of Staphylococcus aureus

Staphylococcus aureus grows in the skin of patients with atopic dermatitis and the associated symptoms are induced by membrane vesicles (MVs). This study explored the effects of slightly acidic electrolyzed water (SAEW) on the expression of virulence factors of S. aureus and MV-induced inflammation to uncover the potential of SAEW as a new treatment method for atopic dermatitis. Expression levels of genes related to virulence factors in S. aureus was assessed and S. aureus-derived MVs were characterized. Moreover, expression level of MV-induced Type I allergic reaction-related genes in RBL2H3 cells was also assessed. Significantly decreased staphylococcal enterotoxin A production and decreased virulence factor-related gene expression were observed after culturing S. aureus in broth supplemented with SAEW at ratios of 1, 2, and 5 per broth. MVs prepared by culturing S. aureus in SAEW-supplemented broth exhibited altered particle size and markedly reduced staphylococcal enterotoxin A content under all addition conditions; moreover, those obtained at a ratio of 1:5 (broth:SAEW) exhibited a reduction in the expression of several proteins associated with hemolytic activity and free iron uptake. The MVs prepared in SAEW-supplemented broth also exhibited remarkably reduced allergy-related gene expression levels in rat cell lines derived from basophilic leukemia-2H3 cells. Overall, SAEW is expected to suppress atopic dermatitis symptoms through the alteration of the properties of S. aureus-derived MVs.

Identification of genes involved in enhanced membrane vesicle formation in Pseudomonas aeruginosa biofilms: surface sensing facilitates vesiculation

Membrane vesicles (MVs) are small spherical structures (20-400 nm) produced by most bacteria and have important biological functions including toxin delivery, signal transfer, biofilm formation, and immunomodulation of the host. Although MV formation is enhanced in biofilms of a wide range of bacterial species, the underlying mechanisms are not fully understood. An opportunistic pathogen, Pseudomonas aeruginosa, causes chronic infections that can be difficult to treat due to biofilm formation. Since MVs are abundant in biofilms, can transport virulence factors to the host, and have inflammation-inducing functions, the mechanisms of enhanced MV formation in biofilms needs to be elucidated to effectively treat infections. In this study, we evaluated the characteristics of MVs in P. aeruginosa PAO1 biofilms, and identified factors that contribute to enhanced MV formation. Vesiculation was significantly enhanced in the static culture; MVs were connected to filamentous substances in the biofilm, and separation between the outer and inner membranes and curvature of the membrane were observed in biofilm cells. By screening a transposon mutant library (8,023 mutants) for alterations in MV formation in biofilms, 66 mutants were identified as low-vesiculation strains (2/3 decrease relative to wild type), whereas no mutant was obtained that produced more MVs (twofold increase). Some transposons were inserted into genes related to biofilm formation, including flagellar motility (flg, fli, and mot) and extracellular polysaccharide synthesis (psl). ΔpelAΔpslA, which does not synthesize the extracellular polysaccharides Pel and Psl, showed reduced MV production in biofilms but not in planktonic conditions, suggesting that enhanced vesiculation is closely related to the synthesis of biofilm matrices in P. aeruginosa. Additionally, we found that blebbing occurred during bacterial attachment. Our findings indicate that biofilm-related factors are closely involved in enhanced MV formation in biofilms and that surface sensing facilitates vesiculation. Furthermore, this work expands the understanding of the infection strategy in P. aeruginosa biofilms.

Tumor-Derived Membrane Vesicles Restrain Migration in Gliomas By Altering Collective Polarization

Mechanobiology is a cornerstone in physiology. However, its role in biomedical applications remains considerably undermined. In this study, we employed cell membrane vesicles (CMVs), which are currently being used as nanodrug carriers, as tactile cues for mechano-regulation of collective cell behaviors. Gliomas, which are among the most resilient brain tumors and have a low patient survival rate, were used as the cell model. We observed that mechanical responses due to the application of glioma- or microglia-derived CMVs resulted in the doubling of the traction stress of glioma cell collectives with a 10-fold increase in the CMV concentration. Glioma-CMVs constrained cell protrusions and hindered their collective migration, with the migration speed of such cells declining by almost 40% compared to the untreated cells. We speculated that the alteration of collective polarization leads to migration speed changes, and this phenomenon was elucidated using the cellular Potts model. In addition to intracellular force modulation and cytoskeletal reorganization, glioma-CMVs altered drug diffusion within glioma spheroids by downregulating the mechano-signaling protein YAP-1 while also marginally enhancing the associated apoptotic events. Our results suggest that glioma-CMVs can be applied as an adjuvant to current treatment approaches to restrict tumor invasion and enhance the penetration of reagents within tumors. Considering the broad impact of mechano-transduction on cell functions, the regulation of cell mechanics through CMVs can provide a foundation for alternative therapeutic strategies.

Vesicle-enriched secretomes alter bacterial competitive abilities and are drivers of evolution in microbial communities

Microbial membrane vesicles can carry compounds that inhibit bacterial growth, but how they impact the fitness of the vesicle-producing bacterial species and influence community dynamics remain unexplored questions. To address these questions, we examined the effect of vesicle-enriched secretomes (VESs) in different single-species and multi-species systems. Effects of VESs on single-species growth dynamics were determined for nine bacterial species belonging to four genera (Escherichia, Salmonella, Pseudomonas and Bacillus) in nutrient-rich and poor growth media. Results showed both species-specific and nutrient-dependent effects of the VESs on bacterial growth. The strongest antagonistic effects were observed for VES isolated from the natural isolates of E. coli, while those isolated from P. aeruginosa PA14 affected the highest number of species. We further demonstrated that these VESs altered the competitive abilities of the species involved in two-species (S. Typhimurium LT2 and S. arizonae) and three-species systems (E. coli, S. Typhimurium LT2 and B. subtilis). Finally, using experimental evolution we showed that different bacterial species could rapidly acquire mutations that abrogated the antagonistic effects of VESs. This study demonstrates how VESs can contribute in shaping microbial communities, both by increasing the competitive ability of a given bacterial species and as a driver of genetic adaptation.

More than just a gel: the extracellular matrixome of Pseudomonas aeruginosa

Armed with an arsenal of protein secretion systems, antibiotic efflux pumps, and the occasional proclivity for explosive self-destruction, Pseudomonas aeruginosa has become a model for the study of bacterial pathogenesis and biofilm formation. There is accruing evidence to suggest that the biofilm matrix-the bioglue that holds the structure together-acts not only in a structural capacity, but is also a molecular "net" whose function is to capture and retain certain secreted products (including proteins and small molecules). In this perspective, we argue that the biofilm matrixome is a distinct extracellular compartment, and one that is differentiated from the bulk secretome. Some of the points we raise are deliberately speculative, but are becoming increasingly accessible to experimental investigation.