Extracellular vesicles: An emerging platform in gram-positive bacteria

Review on bacterial outer membrane vesicles: structure, vesicle formation, separation and biotechnological applications

Outer membrane vesicles (OMVs), shed by Gram-negative bacteria, are spherical nanostructures that play a pivotal role in bacterial communication and host-pathogen interactions. Comprising an outer membrane envelope and encapsulating a variety of bioactive molecules from their progenitor bacteria, OMVs facilitate material and informational exchange. This review delves into the recent advancements in OMV research, providing a comprehensive overview of their structure, biogenesis, and mechanisms of vesicle formation. It also explores their role in pathogenicity and the techniques for their enrichment and isolation. Furthermore, the review highlights the burgeoning applications of OMVs in the field of biomedicine, emphasizing their potential as diagnostic tools, vaccine candidates, and drug delivery vectors.

Protocol for isolating extracellular vesicles from alveolar macrophages phagocytosing MRSA in vitro cell culture models

Extracellular vesicles (EVs) play a crucial role in delivering bioactive cargo in infectious diseases. Here, we present a protocol for isolating EVs from alveolar macrophages (AMs) that phagocytose methicillin-resistant Staphylococcus aureus (MRSA) in vitro cell culture models. We describe steps for bacterial preparation; infection of AMs with MRSA; and isolation, purification, and characterization of EVs. This protocol provides a valuable perspective for studying EVs derived from pathogen-infected immune cells. For complete details on the use and execution of this protocol, please refer to Bai et al.1.

Ligilactobacillus-Derived Extracellular Vesicles Inhibit Growth and Virulence of Enteric Pathogens

Bacterial intra-kingdom communication involves the secretion of outer membrane vesicles as signaling carriers to the target cells. However, limited research exists on extracellular vesicles (EVs) from Gram-positive gut bacteria, their interactions with enteric pathogens, and potential inhibitory effects. In this study, we characterized the structure, protein content, and inhibitory effects of EVs from three new potential probiotic gut symbionts, Ligilactobacillus salivarius UO.C109, Ligilactobacillus saerimneri UO.C121, and Ligilactobacillus salivarius UO.C249. EVs were isolated and characterized using three different methods (ultracentrifugation, density gradient purification, and size exclusion chromatography). The purity, dose-dependency, structure, and proteome profiles of the purified EVs were evaluated. Antibacterial and anti-virulence activities of EV subpopulations were assessed against Salmonella enterica serovar Typhimurium and Campylobacter jejuni. EVs from Lg. salivarius UO.C109 and Lg. saerimneri UO.C121 showed inhibitory activity against S. Typhimurium, whereas EVs from Lg. salivarius UO.C249 inhibited the growth of C. jejuni. Notably, purified F3 fraction exhibited the highest inhibitory activity and was enriched in lysin motif (LysM)-containing proteins, peptidoglycan hydrolases, peptidoglycan recognition proteins (PGRPs), and metallopeptidases, which have been shown to play a prominent role in antimicrobial activities against pathogens. F3 had the highest concentration (73.8%) in the 80-90 nm size compared to the other fractions. Gene expression analysis revealed that EVs from Lg. salivarius UO.C109 and Lg. saerimneri UO.C121 downregulated adhesion and invasion factors in S. Typhimurium. Likewise, EVs from Lg. salivarius UO.C249 reduced pathogenicity gene expression in C. jejuni. This study highlighted the potential of gut bacterial EVs as therapeutic agents against enteric pathogens.

Bacterial extracellular vesicle: A non-negligible component in biofilm life cycle and challenges in biofilm treatments

Bacterial biofilms, especially those formed by pathogens, have been increasingly impacting human health. Bacterial extracellular vesicle (bEV), a kind of spherical membranous structure released by bacteria, has not only been reported to be a component of the biofilm matrix but also plays a non-negligible role in the biofilm life cycle. Nevertheless, a comprehensive overview of the bEVs functions in biofilms remains elusive. In this review, we summarize the biogenesis and distinctive features characterizing bEVs, and consolidate the current literature on their functions and proposed mechanisms in the biofilm life cycle. Furthermore, we emphasize the formidable challenges associated with vesicle interference in biofilm treatments. The primary objective of this review is to raise awareness regarding the functions of bEVs in the biofilm life cycle and lay the groundwork for the development of novel therapeutic strategies to control or even eliminate bacterial biofilms.

Plant memory and communication of encounters

Plants can communicate with each other and other living organisms in a very sophisticated manner. They use biological molecules and even physical cues to establish a molecular dialogue with beneficial organisms as well as with their predators and pathogens. Several studies were recently published that explore how plants communicate with each other about their previous encounters or stressful experiences. However, there is an almost complete lack of knowledge about how these intra- and interspecies communications are directly regulated at the epigenetic level. In this perspective article we provide new hypotheses for the possible epigenetic modifications that regulate plant responses at the communication level.

Utilization of Probiotic-Derived Extracellular Vesicles as Postbiotics and Their Role in Mental Health Therapeutics

As consumers become more interested in healthier lifestyles, the global functional food market is expanding. Probiotics have gained attention because of their numerous health benefits to the host and may even treat various pathological conditions. Probiotics interact with host cells, and particularly, probiotics-derived extracellular vesicles (PEVs) are key factors in the health benefits of probiotics. Additionally, extracellular vesicles are nano-scaled lipid-bilayer particles that carry various biological molecules, indicating potential as new postbiotics that can provide the same health benefits as probiotics while complementing the side effects associated with probiotics. The importance of mental health care is becoming increasingly prominent considering societal conditions, such as the recent aging population and the coronavirus disease 2019 pandemic. However, the response to mental health issues among modern individuals is insufficient, and there is a need for the development of new personalized treatments to overcome the limitations of current mental health therapies. PEVs have various physiological functions, including mediating cellular communication in the central nervous system, which indicates associations among mental disorders. Therefore, we focused on the beneficial effects of PEVs on the brain and mental health. Recent research has shown that PEVs can adjust the expression of brain-derived neurotrophic factors in vitro and in vivo, demonstrating antidepressant and cognitive function improvement effects. This suggests that PEVs have potential as therapeutic agents for improving mental health and treating brain disorders. Based on this, we review these findings and present the beneficial effects of PEVs on mental health and the challenges that need to be addressed.

Arabidopsis apoplast TET8 positively correlates to leaf senescence, and tet3tet8 double mutants are delayed in leaf senescence

Extracellular vesicles (EVs) are membrane-bound exosomes secreted into the apoplast. Two distinct populations of EVs have been described in Arabidopsis: PEN1-associated and TET8-associated. We previously noted early leaf senescence in the pen1 single and pen1pen3 double mutant. Both PEN1 and PEN3 are abundant in EV proteomes suggesting that EVs might regulate leaf senescence in soil-grown plants. We observed that TET8 is more abundant in the apoplast of early senescing pen1 and pen1pen3 mutant rosettes and in older wild-type (WT) rosettes. The increase in apoplast TET8 in the pen1 mutant did not correspond to increased TET8 mRNA levels. In addition, apoplast TET8 was more abundant in the early leaf senescence myb59 mutant, meaning the increase in apoplast TET8 protein during leaf senescence is not dependent on pen1 or pen3. Genetic analysis showed a significant delay in leaf senescence in tet3tet8 double mutants after 6 weeks of growth suggesting that these two tetraspanin paralogs operate additively and are positive regulators of leaf senescence. This is opposite of the effect of pen1 and pen1pen3 mutants that show early senescence and suggest PEN1 to be a negative regulator of leaf senescence. Our work provides initial support that apoplast-localized TET8 in combination with TET3 positively regulates age-related leaf senescence in soil-grown Arabidopsis plants.

Isolation, characterization, and immunomodulatory effects of extracellular vesicles isolated from fish pathogenic Aeromonas hydrophila

Bacterial extracellular vesicles (BEVs) are natural nanocarriers that have shown great potential for biomedical applications such as biomarkers, cancer therapy, immunomodulators, vaccines, wound healing, tissue engineering, and drug carriers. In the present study, BEVs were isolated from the gram-negative bacterium, Aeromonas hydrophila using the ultracentrifugation method and denoted as AhEVs. Using transmission electron microscopy imaging, we confirmed the ultrastructure and spherical shape morphology of AhEVs. Nanoparticle-tracking analysis results showed a mean particle size of 105.5 ± 2.0 nm for AhEVs. Moreover, the particle concentration of AhEVs was 2.34 ± 0.12 × 1011 particles/mL of bacterial supernatant. AhEV-treated fathead minnow (FHM) cells did not show cytotoxicity effects up to 50 μg/mL with no significant decrease in cells. Moreover, no mortality was observed in larval zebrafish up to 50 μg/mL which indicates that the AhEVs are biocompatible at this concentration. Furthermore, fluorescent-labeled AhEVs were internalized into FHM cells. Results of qRT-PCR analysis in FHM cells revealed that cellular pro-inflammatory cytokines such as nuclear factor (NF)-κB, interferon (Ifn), Irf7, interleukin (Il) 8, and Il11 were upregulated while downregulating the expression of anti-inflammatory Il10 in a concentration-dependent manner. AhEV-treated adult zebrafish (5 μg/fish) induced toll-like receptor (tlr) 2 and tlr4; tumor necrosis factor-alpha (tnfα); heat shock protein (hsp) 70; and il10, il6, and il1β in kidney. Protein expression of NF-κB p65 and Tnfα presented amplified levels in the spleen of AhEVs-treated zebrafish. Based on the collective findings, we conclude that AhEVs exhibited morphological and physicochemical characteristics to known EVs of gram (-)ve bacteria. At biocompatible concentrations, the immunomodulatory activity of AhEVs was demonstrated by inducing different immune response genes in FHM cells and zebrafish. Hence, we suggest that AhEVs could be a novel vaccine candidate in fish medicine due to their ability to elicit strong immune responses.

Bacteriophages and bacterial extracellular vesicles, threat or opportunity?

Emergence of antimicrobial-resistant bacteria (AMR) is one of the health major problems worldwide. The scientists are looking for a novel method to treat infectious diseases. Phage therapy is considered a suitable approach for treating infectious diseases. However, there are different challenges in this way. Some biological aspects can probably influence on therapeutic results and further investigations are necessary to reach a successful phage therapy. Bacteriophage activity can influence by bacterial defense system. Bacterial extracellular vesicles (BEVs) are one of the bacterial defense mechanisms which can modify the results of bacteriophage activity. BEVs have the significant roles in the gene transferring, invasion, escape, and spreading of bacteriophages. In this review, the defense mechanisms of bacteria against bacteriophages, especially BEVs secretion, the hidden linkage of BEVs and bacteriophages, and its possible consequences on the bacteriophage activity as well phage therapy will be discussed.

Extracellular vesicles from alveolar macrophages harboring phagocytosed methicillin-resistant Staphylococcus aureus induce necroptosis

Methicillin-resistant Staphylococcus aureus (MRSA) infection, a major cause of hospital- and community-acquired pneumonia, still has a high mortality rate. Extracellular vesicles (EVs), as crucial mediators of intercellular communication, have a significant impact on infectious diseases. However, the role of EVs from alveolar macrophages (AMs) in MRSA pneumonia remains unclear. We report that AMs phagocytose MRSA and release more EVs in mice with MRSA pneumonia. EVs from AMs harboring phagocytosed MRSA exhibit significant proinflammatory effects and induce necroptosis by delivering tumor necrosis factor α (TNF-α) and miR-146a-5p. Mechanically, the upregulated miR-146a-5p in these EVs enhances the phosphorylation of RIPK1, RIPK3, and MLKL by targeting TNF receptor-associated factor 6 (TRAF6), thereby promoting TNF-α-induced necroptosis. The combination of a TNF-α antagonist and an miR-146a-5p antagomir effectively improves the outcomes of mice with MRSA pneumonia. Overall, we reveal the pronecrotic effect of EVs from MRSA-infected AMs and provide a promising target for the prevention and treatment of MRSA pneumonia.

Cargo exchange between human and bacterial extracellular vesicles in gestational tissues: a new paradigm in communication and immune development

Host-bacteria and bacteria-bacteria interactions can be facilitated by extracellular vesicles (EVs) secreted by both human and bacterial cells. Human and bacterial EVs (BEVs) propagate and transfer immunogenic cargos that may elicit immune responses in nearby or distant recipient cells/tissues. Hence, direct colonization of tissues by bacterial cells is not required for immunogenic stimulation. This phenomenon is important in the feto-maternal interface, where optimum tolerance between the mother and fetus is required for a successful pregnancy. Though the intrauterine cavity is widely considered sterile, BEVs from diverse sources have been identified in the placenta and amniotic cavity. These BEVs can be internalized by human cells, which may help them evade host immune surveillance. Though it appears logical, whether bacterial cells internalize human EVs or human EV cargo is yet to be determined. However, the presence of BEVs in placental tissues or amniotic cavity is believed to trigger a low-grade immune response that primes the fetal immune system for ex-utero survival, but is insufficient to disrupt the progression of pregnancy or cause immune intolerance required for adverse pregnancy events. Nevertheless, the exchange of bioactive cargos between human and BEVs, and the mechanical underpinnings and health implications of such interactions, especially during pregnancy, are still understudied. Therefore, while focusing on the feto-maternal interface, we discussed how human cells take up BEVs and whether bacterial cells take up human EVs or their cargo, the exchange of cargos between human and BEVs, host cell (feto-maternal) inflammatory responses to BEV immunogenic stimulation, and associations of these interactions with fetal immune priming and adverse reproductive outcomes such as preeclampsia and preterm birth.

Enterococcus faecalis Extracellular Vesicles Promote Apical Periodontitis

Enterococcus faecalis is an important contributor to the persistence of chronic apical periodontitis. However, the mechanism by which E. faecalis infection in the root canals and dentinal tubules affects periapical tissue remains unclear. Bacterial extracellular vesicles (EVs) act as natural carriers of microbe-associated molecular patterns (MAMPs) and have recently attracted considerable attention. In this study, we investigated the role of EVs derived from E. faecalis in the pathogenesis of apical periodontitis. We observed that E. faecalis EVs can induce inflammatory bone destruction in the periapical areas of mice. Double-labeling immunofluorescence indicated that M1 macrophage infiltration was increased by E. faecalis EVs in apical lesions. Moreover, in vitro experiments demonstrated the internalization of E. faecalis EVs into macrophages. Macrophages tended to polarize toward the M1 profile after treatment with E. faecalis EVs. Pattern recognition receptors (PRRs) can recognize MAMPs of bacterial EVs and, in turn, trigger inflammatory responses. Thus, we performed further mechanistic exploration, which showed that E. faecalis EVs considerably increased the expression of NOD2, a cytoplasmic PRR, and that inhibition of NOD2 markedly reduced macrophage M1 polarization induced by E. faecalis EVs. RIPK2 ubiquitination is a major downstream of NOD2. We also observed increased RIPK2 ubiquitination in macrophages treated with E. faecalis EVs, and E. faecalis EV-induced macrophage M1 polarization was notably alleviated by the RIPK2 ubiquitination inhibitor. Our study revealed the potential for EVs to be considered a virulence factor of E. faecalis and found that E. faecalis EVs can promote macrophage M1 polarization via NOD2/RIPK2 signaling. To our knowledge, this is the first report to investigate apical periodontitis development from the perspective of bacterial vesicles and demonstrate the role and mechanism of E. faecalis EVs in macrophage polarization. This study expands our understanding of the pathogenic mechanism of E. faecalis and provides novel insights into the pathogenesis of apical periodontitis.

Isolation and Characteristics of Extracellular Vesicles Produced by Probiotics: Yeast Saccharomyces boulardii CNCM I-745 and Bacterium Streptococcus salivarius K12

Numerous probiotic microorganisms have repeatedly been shown to produce nanometer-sized structures named extracellular vesicles (EVs). Recently, it has been suggested that similarly to whole microbial cells, EVs produced by probiotics may also demonstrate health benefits to the host, while their application does not involve the risk of infection caused by live microorganisms. In this work, we isolated EVs from two probiotic species originating from different taxonomic domains - yeast Saccharomyces boulardii CNCM I-745 and bacterium Streptococcus salivarius K12. The diameters of S. boulardii EVs were about 142 nm and for S. salivarius EVs about 123 nm. For S. boulardii EVs, 1641 proteins and for S. salivarius EVs, 466 proteins were identified with a liquid chromatography-coupled tandem mass spectrometry and then functionally classified. In both microbial species, metabolic proteins significantly contributed to the cargo of EVs comprising 25% and 26% of all identified vesicular proteins for fungi and bacteria, respectively. Moreover, enzymes associated with cell wall rearrangement, including enzymatically active glucanases, were also identified in EVs. Furthermore, probiotic EVs were shown to influence host cells and stimulate the production of IL-1β and IL-8 by the human monocytic cell line THP-1, and, at the same time, did not cause any remarkable reduction in the survival rate of Galleria mellonella larvae in this invertebrate model commonly used to evaluate microbial EV toxicity. These observations suggest that the EVs produced by the investigated probiotic microorganisms may be promising structures for future use in pro-health applications.

The Emerging Role of Human Gut Bacteria Extracellular Vesicles in Mental Disorders and Developing New Pharmaceuticals

In recent years, further evidence has emerged regarding the involvement of extracellular vesicles in various human physiopathological conditions such as Alzheimer's disease, Parkinson's disease, irritable bowel syndrome, and mental disorders. The biogenesis and cargo of such vesicles may reveal their impact on human health nd disease and set the underpinnings for the development of novel chemical compounds and pharmaceuticals. In this review, we examine the link between bacteria-derived exosomes in the gastrointestinal tract and mental disorders, such as depression and anxiety disorders. Crucially, we focus on whether changes in the gut environment affect the human mental state or the other way around. Furthermore, the possibility of handling bacteria-derived exosomes as vectors of chemicals to treat such conditions is examined.

Arabidopsis Apoplast TET8 Positively Correlates to Leaf Senescence and tet3tet8 Double Mutants are Delayed in Leaf Senescence

Extracellular vesicles (EVs) are membrane-bound exosomes secreted into the apoplast. Two distinct populations of EVs have been described in Arabidopsis: PEN1-associated and TET8-associated. We previously noted early leaf senescence in the pen1 single and pen1pen3 double mutant. Both PEN1 and PEN3 are abundant in EV proteomes suggesting EVs might regulate leaf senescence in soil-grown plants. We observed that TET8 is more abundant in the apoplast of early senescing pen1 and pen1pen3 mutant rosettes and in older WT rosettes. The increase in apoplast TET8 in the pen1 mutant did not correspond to increased TET8 mRNA levels. In addition, apoplast TET8 was more abundant in the early leaf senescence myb59 mutant, meaning the increase in apoplast TET8 protein during leaf senescence is not dependent on pen1 or pen3 . Genetic analysis showed a significant delay in leaf senescence in tet3tet8 double mutants after six weeks of growth suggesting that these two tetraspanin paralogs operate additively and are positive regulators of leaf senescence. This is opposite of the effect of pen1 and pen1pen3 mutants that show early senescence and suggest PEN1 to be a negative regulator of leaf senescence. Our work provides initial support that PEN1-associated EVs and TET8-associated EVs may have opposite effects on soil-grown plants undergoing age-related leaf senescence.

Immunomodulatory properties of Bacillus subtilis extracellular vesicles on rainbow trout intestinal cells and splenic leukocytes

Extracellular vesicles (EVs) are cell-derived membrane-surrounded vesicles that carry bioactive molecules. Among EVs, outer membrane vesicles (OMVs), specifically produced by Gram-negative bacteria, have been extensively characterized and their potential as vaccines, adjuvants or immunotherapeutic agents, broadly explored in mammals. Nonetheless, Gram-positive bacteria can also produce bilayered spherical structures from 20 to 400 nm involved in pathogenesis, antibiotic resistance, nutrient uptake and nucleic acid transfer. However, information regarding their immunomodulatory potential is very scarce, both in mammals and fish. In the current study, we have produced EVs from the Gram-positive probiotic Bacillus subtilis and evaluated their immunomodulatory capacities using a rainbow trout intestinal epithelial cell line (RTgutGC) and splenic leukocytes. B. subtilis EVs significantly up-regulated the transcription of several pro-inflammatory and antimicrobial genes in both RTgutGC cells and splenocytes, while also up-regulating many genes associated with B cell differentiation in the later. In concordance, B. subtilis EVs increased the number of IgM-secreting cells in splenocyte cultures, while at the same time increased the MHC II surface levels and antigen-processing capacities of splenic IgM+ B cells. Interestingly, some of these experiments were repeated comparing the effects of B. subtilis EVs to EVs obtained from another Bacillus species, Bacillus megaterium, identifying important differences. The data presented provides evidence of the immunomodulatory capacities of Gram-positive EVs, pointing to the potential of B. subtilis EVs as adjuvants or immunostimulants for aquaculture.

Immunomodulatory responses of extracellular vesicles released by gram-positive fish pathogen Streptococcus parauberis

Bacterial extracellular vesicles (BEVs) are nanosized structures that play a role in intercellular communication and transport of bioactive molecules. Streptococcus parauberis is a Gram-positive pathogenic bacterium that causes "Streptococcosis" in fish. In this study, we isolated S. parauberis-derived extracellular vesicles (SpEVs), and then physicochemical and immunomodulatory properties were determined to elucidate their biological functions. Initially, the biogenesis of SpEVs was detected using field emission scanning electron microscopy, which revealed that secretory phase SpEVs attached to the outer surface of S. parauberis. SpEVs had an average particle diameter and zeta potential of 168.3 ± 6.5 nm and -17.96 ± 2.11 mV, respectively. Field emission transmission electron microscopy analysis confirmed the presence of round or oval-shaped SpEVs with clear membrane margins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis results showed three sharp protein bands when SpEVs were stained with Coomassie blue. In vitro toxicity of SpEVs was assayed using the murine macrophage RAW 264.7 cells and we observed no significant (p < 0.05) viability reduction up to 50 μg/mL qRT-PCR results revealed that SpEVs-treated (5 and 10 μg/mL) RAW 264.7 cells significantly (p < 0.05) induced the mRNA of proinflammatory (Il1β, Il6, and Tnfα) and anti-inflammatory (Il10) cytokines in a concentration-dependent manner. In vivo immunomodulatory effects of SpEVs were investigated by injecting SpEVs (5 and 10 μg/fish) into adult zebrafish. Transcriptional analysis based on qRT-PCR indicates significant (p < 0.05) upregulation of proinflammatory (il1β, il6, and tnfα) and anti-inflammatory (il10) genes in a concentration-dependent manner in zebrafish kidney. Further, protein expression results in zebrafish spleen tissue confirmed the immunomodulatory activity of SpEVs. In conclusion, SpEVs display the characteristics of BEVs and immunomodulatory activities, suggesting their potential application as vaccine candidate.

Unveiling clinical applications of bacterial extracellular vesicles as natural nanomaterials in disease diagnosis and therapeutics

Bacterial extracellular vesicles (BEVs) are naturally occurring bioactive membrane-bound nanoparticles released by both gram-negative and gram-positive bacterial species, exhibiting a multifaceted role in mediating host-microbe interactions across various physiological conditions. Increasing evidence supports BEVs as essential mediators of cell-to-cell communicaiton, influencing bacterial pathogenicity, disease mechanisms, and modulating the host immune response. However, the extent to which these BEV-mediated actions can be leveraged to predict disease onset, guide treatment strategies, and determine clinical outcomes remains uncertain, particularly in terms of their clinical translation potentials. This review briefly describes BEV biogenesis and their internalisation by recipient cells and summarises methods for isolation and characterization, essential for understanding their composition and cargo. Further, it discusses the potential of biofluid-associated BEVs as biomarkers for various diseases, spanning both cancer and non-cancerous conditions. Following this, we outline the ongoing human clinical trials of using BEVs for vaccine development. In addition to disease diagnostics, this review explores the emerging research of using natural or engineered BEVs as smart nanomaterials for applications in anti-cancer therapy and bone regeneration. This discussion extends to key factors for unlocking the clinical potential of BEVs, such as standardization of BEV isolation and characterisation, as well as other hurdles in translating these findings to the clinical setting. We propose that addressing these hurdles through collaborative research efforts and well-designed clinical trials holds the key to fully harnessing the clinical potential of BEVs. As this field advances, this review suggests that BEV-based nanomedicine has the potential to revolutionize disease management, paving the way for innovative diagnosis, therapeutics, and personalized medicine approaches. STATEMENT OF SIGNIFICANCE: Extracellular vesicles (EVs) from both host cells and bacteria serve as multifunctional biomaterials and are emerging in the fields of biomedicine, bioengineering, and biomaterials. However, the majority of current studies focus on host-derived EVs, leaving a gap in comprehensive research on bacteria-derived EVs (BEVs). Although BEVs offer an attractive option as nanomaterials for drug delivery systems, their unique nanostructure and easy-to-modify functions make them a potential method for disease diagnosis and treatment as well as vaccine development. Our work among the pioneering studies investigating the potential of BEVs as natural nanobiomaterials plays a crucial role in both understanding the development of diseases and therapeutic interventions.

Applications of Urinary Extracellular Vesicles in the Diagnosis and Active Surveillance of Prostate Cancer

Prostate cancer is the most common non-cutaneous cancer among men in the UK, causing significant health and economic burdens. Diagnosis and risk prognostication can be challenging due to the genetic and clinical heterogeneity of prostate cancer as well as uncertainties in our knowledge of the underlying biology and natural history of disease development. Urinary extracellular vesicles (EVs) are microscopic, lipid bilayer defined particles released by cells that carry a variety of molecular cargoes including nucleic acids, proteins and other molecules. Urine is a plentiful source of prostate-derived EVs. In this narrative review, we summarise the evidence on the function of urinary EVs and their applications in the evolving field of prostate cancer diagnostics and active surveillance. EVs are implicated in the development of all hallmarks of prostate cancer, and this knowledge has been applied to the development of multiple diagnostic tests, which are largely based on RNA and miRNA. Common gene probes included in multi-probe tests include PCA3 and ERG, and the miRNAs miR-21 and miR-141. The next decade will likely bring further improvements in the diagnostic accuracy of biomarkers as well as insights into molecular biological mechanisms of action that can be translated into opportunities in precision uro-oncology.

Harnessing Nature's Defence: The Antimicrobial Efficacy of Pasteurised Cattle Milk-Derived Extracellular Vesicles on Staphylococcus aureus ATCC 25923

Increasing antimicrobial resistance (AMR) challenges conventional antibiotics, prompting the search for alternatives. Extracellular vesicles (EVs) from pasteurised cattle milk offer promise, due to their unique properties. This study investigates their efficacy against five pathogenic bacteria, including Staphylococcus aureus ATCC 25923, aiming to combat AMR and to develop new therapies. EVs were characterised and tested using various methods. Co-culture experiments with S. aureus showed significant growth inhibition, with colony-forming units decreasing from 2.4 × 105 CFU/mL (single dose) to 7.4 × 104 CFU/mL (triple doses) after 12 h. Milk EVs extended lag time (6 to 9 h) and increased generation time (2.8 to 4.8 h) dose-dependently, compared to controls. In conclusion, milk EVs exhibit dose-dependent inhibition against S. aureus, prolonging lag and generation times. Despite limitations, this suggests their potential in addressing AMR.

Extracellular vesicles from Staphylococcus aureus promote the pathogenicity of Pseudomonas aeruginosa

Co-infections with Staphylococcus aureus and Pseudomonas aeruginosa are common in patients with chronic wounds, but little is known about their synergistic effect mediated by extracellular vesicles (EVs). In this study, we investigated the effect of EVs derived from S. aureus (SaEVs) on the pathogenicity of P. aeruginosa. By using lipophilic dye, we could confirm the fusion between SaEV and P. aeruginosa membranes. However, SaEVs did not alter the growth and antibiotic susceptible pattern of P. aeruginosa. Differential proteomic analysis between SaEV-treated and non-treated P. aeruginosa was performed, and the results revealed that lipopolysaccharide (LPS) biosynthesis protein in P. aeruginosa significantly increased after SaEV-treatment. Regarding this result, we also found that SaEVs promoted LPS production, biofilm formation, and expression of polysaccharide polymerization-related genes in P. aeruginosa. Furthermore, invasion of epithelial cells by SaEV-pretreated P. aeruginosa was enhanced. On the other hand, uptake of P. aeruginosa by RAW 264.7 macrophages was impaired after pretreatment P. aeruginosa with SaEVs. Proteomic analysis SaEVs revealed that SaEVs contain the proteins involving in host cell colonization, inhibition of host immune response, anti-phagocytosis of the macrophages, and protein translocation and iron uptake of S. aureus. In conclusion, SaEVs serve as a mediator that promote P. aeruginosa pathogenicity by enhancing LPS biosynthesis, biofilm formation, epithelial cell invasion, and macrophage uptake impairment.

Bacterial extracellular vesicles: Modulation of biofilm and virulence properties

Microbial pathogens cause persistent infections by forming biofilms and producing numerous virulence factors. Bacterial extracellular vesicles (BEVs) are nanostructures produced by various bacterial species vital for molecular transport. BEVs include various components, including lipids (glycolipids, LPS, and phospholipids), nucleic acids (genomic DNA, plasmids, and short RNA), proteins (membrane proteins, enzymes, and toxins), and quorum-sensing signaling molecules. BEVs play a major role in forming extracellular polymeric substances (EPS) in biofilms by transporting EPS components such as extracellular polysaccharides, proteins, and extracellular DNA. BEVs have been observed to carry various secretory virulence factors. Thus, BEVs play critical roles in cell-to-cell communication, biofilm formation, virulence, disease progression, and resistance to antimicrobial treatment. In contrast, BEVs have been shown to impede early-stage biofilm formation, disseminate mature biofilms, and reduce virulence. This review summarizes the current status in the literature regarding the composition and role of BEVs in microbial infections. Furthermore, the dual functions of BEVs in eliciting and suppressing biofilm formation and virulence in various microbial pathogens are thoroughly discussed. This review is expected to improve our understanding of the use of BEVs in determining the mechanism of biofilm development in pathogenic bacteria and in developing drugs to inhibit biofilm formation by microbial pathogens. STATEMENT OF SIGNIFICANCE: Bacterial extracellular vesicles (BEVs) are nanostructures formed by membrane blebbing and explosive cell lysis. It is essential for transporting lipids, nucleic acids, proteins, and quorum-sensing signaling molecules. BEVs play an important role in the formation of the biofilm's extracellular polymeric substances (EPS) by transporting its components, such as extracellular polysaccharides, proteins, and extracellular DNA. Furthermore, BEVs shield genetic material from nucleases and thermodegradation by packaging it during horizontal gene transfer, contributing to the transmission of bacterial adaptation determinants like antibiotic resistance. Thus, BEVs play a critical role in cell-to-cell communication, biofilm formation, virulence enhancement, disease progression, and drug resistance. In contrast, BEVs have been shown to prevent early-stage biofilm, disperse mature biofilm, and reduce virulence characteristics.

Outer membrane vesicles as a platform for the discovery of antibodies to bacterial pathogens

Bacterial outer membrane vesicles (OMVs) are nanosized spheroidal particles shed by gram-negative bacteria that contain biomolecules derived from the periplasmic space, the bacterial outer membrane, and possibly other compartments. OMVs can be purified from bacterial culture supernatants, and by genetically manipulating the bacterial cells that produce them, they can be engineered to harbor cargoes and/or display molecules of interest on their surfaces including antigens that are immunogenic in mammals. Since OMV bilayer-embedded components presumably maintain their native structures, OMVs may represent highly useful tools for generating antibodies to bacterial outer membrane targets. OMVs have historically been utilized as vaccines or vaccine constituents. Antibodies that target bacterial surfaces are increasingly being explored as antimicrobial agents either in unmodified form or as targeting moieties for bactericidal compounds. Here, we review the properties of OMVs, their use as immunogens, and their ability to elicit antibody responses against bacterial antigens. We highlight antigens from bacterial pathogens that have been successfully targeted using antibodies derived from OMV-based immunization and describe opportunities and limitations for OMVs as a platform for antimicrobial antibody development. KEY POINTS: • Outer membrane vesicles (OMVs) of gram-negative bacteria bear cell-surface molecules • OMV immunization allows rapid antibody (Ab) isolation to bacterial membrane targets • Review and analysis of OMV-based immunogens for antimicrobial Ab development.

SMR peptide antagonizes Staphylococcus aureus biofilm formation

The emergence and international dissemination of multi-drug resistant Staphylococcus aureus (S. aureus) strains challenge current antibiotic-based therapies, representing an urgent threat to public health worldwide. In the U.S. alone, S. aureus infections are responsible for 11,000 deaths and 500,000 hospitalizations annually. Biofilm formation is a major contributor to antibiotic tolerance and resistance-induced delays in empirical therapy with increased infection severity, frequency, treatment failure, and mortality. Developing novel treatment strategies to prevent and disrupt biofilm formation is imperative. In this article, we test the Secretion Modification Region (SMR) peptides for inhibitory effects on resistant S. aureus biofilm-forming capacity by targeting the molecular chaperone DnaK. The dose effect of SMR peptides on biofilm formation was assessed using microtiter plate methods and confocal microscopy. Interaction between the antagonist and DnaK was determined by immune precipitation with anti-Flag M2 Affinity and Western blot analysis. Increasing SMR peptide concentrations exhibited increasing blockade of S. aureus biofilm formation with significant inhibition found at 18 µM, 36 µM, and 72 µM. This work supports the potential therapeutic benefit of SMR peptides in reducing biofilm viability and could improve the susceptibility to antimicrobial agents.IMPORTANCEThe development of anti-biofilm agents is critical to restoring bacterial sensitivity, directly combating the evolution of resistance, and overall reducing the clinical burden related to pervasive biofilm-mediated infections. Thus, in this study, the SMR peptide, a novel small molecule derived from the HIV Nef protein, was preliminarily explored for anti-biofilm properties. The SMR peptide was shown to effectively target the molecular chaperone DnaK and inhibit biofilm formation in a dose-dependent manner. These results support further investigation into the mechanism of SMR peptide-mediated biofilm formation and inhibition to benefit rational drug design and the identification of therapeutic targets.

Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches

Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly.

BACTERIAL EXTRACELLULAR VESICLES IN THE REGULATION OF INFLAMMATORY RESPONSE AND HOST-MICROBE INTERACTIONS

ABSTRACT

Extracellular vesicles (EVs) are a new revelation in cross-kingdom communication, with increasing evidence showing the diverse roles of bacterial EVs (BEVs) in mammalian cells and host-microbe interactions. Bacterial EVs include outer membrane vesicles released by gram-negative bacteria and membrane vesicles generated from gram-positive bacteria. Recently, BEVs have drawn attention for their potential as biomarkers and therapeutic tools because they are nano-sized and can deliver bacterial cargo into host cells. Importantly, exposure to BEVs significantly affects various physiological and pathological responses in mammalian cells. Herein, we provide a comprehensive overview of the various effects of BEVs on host cells (i.e., immune cells, endothelial cells, and epithelial cells) and inflammatory/infectious diseases. First, the biogenesis and purification methods of BEVs are summarized. Next, the mechanisms and pathways identified by BEVs that stimulate either proinflammatory or anti-inflammatory responses are highlighted. In addition, we discuss the mechanisms by which BEVs regulate host-microbe interactions and their effects on the immune system. Finally, this review focuses on the contribution of BEVs to the pathogenesis of sepsis/septic shock and their therapeutic potential for the treatment of sepsis.

Gram-negative bacterial sRNAs encapsulated in OMVs: an emerging class of therapeutic targets in diseases

Small regulatory RNAs (sRNAs) encapsulated in outer membrane vesicles (OMVs) are critical post-transcriptional regulators of gene expression in prokaryotic and eukaryotic organisms. OMVs are small spherical structures released by Gram-negative bacteria that serve as important vehicles for intercellular communication and can also play an important role in bacterial virulence and host-pathogen interactions. These molecules can interact with mRNAs or proteins and affect various cellular functions and physiological processes in the producing bacteria. This review aims to provide insight into the current understanding of sRNA localization to OMVs in Gram-negative bacteria and highlights the identification, characterization and functional implications of these encapsulated sRNAs. By examining the research gaps in this field, we aim to inspire further exploration and progress in investigating the potential therapeutic applications of OMV-encapsulated sRNAs in various diseases.

New Perspectives on Crosstalks Between Bacterial Regulatory RNAs from Outer Membrane Vesicles and Eukaryotic Cells

Regulatory small RNAs (sRNAs) help the bacteria to survive harsh environmental conditions by posttranscriptional regulation of genes involved in various biological pathways including stress responses, homeostasis, and virulence. These sRNAs can be found carried by different membrane-bound vesicles like extracellular vesicles (EVs), membrane vesicles (MVs), or outer membrane vesicles (OMVs). OMVs provide myriad functions in bacterial cells including carrying a cargo of proteins, lipids, and nucleic acids including sRNAs. A few interesting studies have shown that these sRNAs can be transported to the host cell by membrane vesicles and can regulate the host immune system. Although there is evidence that sRNAs can be exported to host cells and sometimes can even cross the blood-brain barrier, the exact mechanism is still unknown. In this review, we investigated the new techniques implemented in various studies, to elucidate the crosstalks between bacterial cells and human immune systems by membrane vesicles carrying bacterial regulatory sRNAs.

Assessing In Vivo Bacterial Extracellular Vesicle (BEV) Biodistribution Using Fluorescent Lipophilic Membrane Stains

Bacterial extracellular vesicles (BEVs) are nano-size vesicles containing a cargo of bioactive molecules that can play key roles in microbe-microbe and microbe-host interactions. In tracking their biodistribution in vivo, BEVs can cross several physical host barriers including the intestinal epithelium, vascular endothelium, and blood-brain-barrier (BBB) to ultimately accumulate in tissues such as the liver, lungs, spleen, and the brain. This tissue-specific dissemination has been exploited for the delivery of biomolecules such as vaccines for mucosal delivery. Although numerous strategies for labeling and tracking BEVs have been described, most have constraints that impact on interpreting in vivo bioimaging patterns. Here, we describe a general method for labeling BEVs using lipophilic fluorescent membrane stains which can be adopted by non-expert users. We also describe how the procedure can be used to overcome potential limitations. Furthermore, we outline methods of quantitative ex vivo tissue imaging that can be used to evaluate BEV organ trafficking.

Lactobacillus from the Altered Schaedler Flora maintain IFNγ homeostasis to promote behavioral stress resilience

The gut microbiome consists of trillions of bacteria, fungi, and viruses that inhabit the digestive tract. These communities are sensitive to disruption from environmental exposures ranging from diet changes to illness. Disruption of the community of lactic acid producing bacteria, Lactobaccillacea, has been well documented in mood disorders and stress exposure. In fact, oral supplement with many Lactobacillus species can ameliorate these effects, preventing depression- and anxiety-like behavior. Here, we utilize a gnotobiotic mouse colonized with the Altered Schaedler Flora to remove the two native species of Lactobaccillacea: L. intestinalis and L. murinus. Using this microbial community, we found that the Lactobacillus species themselves, and not the disrupted microbial communities are protective from environmental stressors. Further, we determine that Lactobaccillacea are maintaining homeostatic IFNγ levels which are mediating these behavioral and circuit level responses. By utilizing the Altered Schaedler Flora, we have gained new insight into how probiotics influence behavior and provide novel methods to study potential therapies to treat mood disorders.

Monkeypox Virus (MPXV) Infection: A Review

Monkeypox is a viral disease; its outbreak was recently declared a global emergency by the World Health Organization. For the first time, a monkeypox virus (MPXV)-infected patient was found in India. Various researchers back-to-back tried to find the solution to this health emergency just after COVID-19. In this review, we discuss the current outbreak status of India, its transmission, virulence factors, symptoms, treatment, and the preventive guidelines generated by the Indian Health Ministry. We found that monkeypox virus (MPXV) disease is different from smallpox, and the age group between 30-40 years old is more prone to MPXV disease. We also found that, besides homosexuals, gays, bisexuals, and non-vegetarians, it also affects normal straight men and women who have no history of travel. Close contact should be avoided from rats, monkeys and sick people who are affected by monkeypox. To date, there are no monkeypox drugs, but Tecovirimat is more effective than other drugs that are used for other viral diseases like smallpox. Therefore, we need to develop an effective antiviral agent against the virulence factor of MXPV.

Gut microbial metabolic signatures in diabetes mellitus and potential preventive and therapeutic applications

Diabetes mellitus can be subdivided into several categories based on origin and clinical characteristics. The most common forms of diabetes are type 1 (T1D), type 2 diabetes (T2D) and gestational diabetes mellitus (GDM). T1D and T2D are chronic diseases affecting around 537 million adults worldwide and it is projected that these numbers will increase by 12% over the next two decades, while GDM affects up to 30% of women during pregnancy, depending on diagnosis methods. These forms of diabetes have varied origins: T1D is an autoimmune disease, while T2D is commonly associated with, but not limited to, certain lifestyle patterns and GDM can result of a combination of genetic predisposition and pregnancy factors. Despite some pathogenic differences among these forms of diabetes, there are some common markers associated with their development. For instance, gut barrier impairment and inflammation associated with an unbalanced gut microbiota and their metabolites may be common factors in diabetes development and progression. Here, we summarize the microbial signatures that have been linked to diabetes, how they are connected to diet and, ultimately, the impact on metabolite profiles resulting from host-gut microbiota-diet interactions. Additionally, we summarize recent advances relating to promising preventive and therapeutic interventions focusing on the targeted modulation of the gut microbiota to alleviate T1D, T2D and GDM.

Bacterial membrane vesicles in the pathogenesis and treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic and debilitating condition of relapsing and remitting inflammation in the gastrointestinal tract. Conventional therapeutic approaches for IBD have shown limited efficacy and detrimental side effects, leading to the quest for novel and effective treatment options for the disease. Bacterial membrane vesicles (MVs) are nanosized lipid particles secreted by lysis or blebbing processes from both Gram-negative and Gram-positive bacteria. These vesicles, known to carry bioactive components, are facsimiles of the parent bacterium and have been implicated in the onset and progression, as well as in the amelioration of IBD. This review discusses the overview of MVs and their impact in the pathogenesis, diagnosis, and treatment of IBD. We further discuss the technical challenges facing this research area and possible research questions addressing these challenges. We summarize recent advances in the diverse relationship between IBD and MVs, and the application of this knowledge as a viable and potent therapeutic strategy for IBD.

Diagnostic and therapeutic value of EVs in lungs diseases and inflammation

Extracellular vesicles (EVs) are membrane-derived messengers which have been playing an important role in the inflammation and pathogenesis of lung diseases. EVs contain varieties of DNA, RNA, and membrane receptors through which they work as a delivery system for bioactive molecules as well as intracellular communicators. EV signaling mediates tumor progression and metastasis. EVs are linked with many diseases and perform a diagnostic role in lung injury and inflammation so are used to diagnose the severity of diseases. EVs containing a variety of biomolecules communicate with the recipient cells during pathophysiological mechanisms thereby acquiring the attention of clinicians toward the diagnostic and therapeutic potential of EVs in different lung diseases. In this review, we summarize the role of EVs in inflammation with an emphasis on their potential as a novel candidate in the diagnostics and therapeutics of chronic obstructive pulmonary disease, asthma, and sarcoidosis.

Dietary Lactobacillus rhamnosus GG extracellular vesicles enhance antiprogrammed cell death 1 (anti-PD-1) immunotherapy efficacy against colorectal cancer

There is a need to explore combination therapy to improve the efficacy of immunotherapy for colorectal cancer through food probiotics. In this study, extracellular vesicles (EV) derived from Lactobacillus rhamnosus GG (LGG-EV) were successfully isolated. Adjusting the culture temperature to 30 °C led to an elevated LGG-EV yield, and the addition of penicillin resulted in a decrease in particle size. In addition, LGG-EV have better gastrointestinal tract stability in a Ca2+ environment in vivo and in vitro. Oral administration of LGG-EV synergistically improved anti-PD-1 immunotherapy efficacy against colorectal cancer. Mechanistically, LGG-EV modulated intestinal immunity by increasing the CD8+ T/CD4+ T cell ratio in mesenteric lymph nodes and enhancing the ratio of MHC II+ DC cells, CD4+ T cells, and CD8+ T cells in tumor tissues. Meanwhile, the diversity of the gut microbiota and the abundance of beneficial bacteria, such as Lactobacillus, increased in the combined-treatment mice. In addition, there were significant changes in the levels of serum metabolites associated with the microbiota and anti-tumor effects, including uridine, which was elevated by the combination of anti-PD-1 and LGG-EV treatment. Our findings provide theoretical and mechanistic insights into the development of LGG-EV as postbiotics in combination with immune checkpoint inhibitors for cancer therapy.

Extracellular Vesicles and Their Role in Lung Infections

Lung infections are one of the most common causes of death and morbidity worldwide. Both bacterial and viral lung infections cause a vast number of infections with varying severities. Extracellular vesicles (EVs) produced by different cells due to infection in the lung have the ability to modify the immune system, leading to either better immune response or worsening of the disease. It has been shown that both bacteria and viruses have the ability to produce their EVs and stimulate the immune system for that. In this review, we investigate topics from EV biogenesis and types of EVs to lung bacterial and viral infections caused by various bacterial species. Mycobacterium tuberculosis, Staphylococcus aureus, and Streptococcus pneumoniae infections are covered intensively in this review. Moreover, various viral lung infections, including SARS-CoV-2 infections, have been depicted extensively. In this review, we focus on eukaryotic-cell-derived EVs as an important component of disease pathogenesis. Finally, this review holds high novelty in its findings and literature review. It represents the first time to cover all different information on immune-cell-derived EVs in both bacterial and viral lung infections.

Extracellular Vesicles and Bacteriophages: New Directions in Environmental Biocolloid Research

There is a long-standing appreciation among environmental engineers and scientists regarding the importance of biologically derived colloidal particles and their environmental fate. This interest has been recently renewed in considering bacteriophages and extracellular vesicles, which are each poised to offer engineers unique insights into fundamental aspects of environmental microbiology and novel approaches for engineering applications, including advances in wastewater treatment and sustainable agricultural practices. Challenges persist due to our limited understanding of interactions between these nanoscale particles with unique surface properties and their local environments. This review considers these biological particles through the lens of colloid science with attention given to their environmental impact and surface properties. We discuss methods developed for the study of inert (nonbiological) particle-particle interactions and the potential to use these to advance our understanding of the environmental fate and transport of extracellular vesicles and bacteriophages.

Cell wall is a dead metaphor

It was recently suggested to end the usage of the term cell wall in microbiology (including prokaryotes and fungi) because it represented an inappropriate and potentially misleading metaphor (Casadevall and Gow, 2022). The analysis of the arguments for such a move from the viewpoint of the plant physiologist indicates that the suggestion is based on misunderstandings, first, of the early history of cell biology and its terminology; second, of the development of modern concepts of cell wall function since the late 19th century; and third, of the nature of metaphors and their role in scientific communication. We conclude that misconceptions concerning cell walls may arise due to pedagogical shortcomings in introducing students to our technical terminology rather than from the fact that part of this terminology originated from metaphors.

Extracellular vesicles as a novel mediator of interkingdom communication

Extracellular vesicles (EVs) are nanosized lipid bilayer-delimited particles secreted from almost all types of cells including bacteria, mammals and plants, and are presumed to be mediators of intercellular communication. Bacterial extracellular vesicles (BEVs) are nanoparticles with diverse diameters, ranging from 20 to 400 nm. BEVs are composed of soluble microbial metabolites, including nucleic acid, proteins, lipoglycans, and short-chain fatty acids (SCFAs). In addition, EVs may contain quorum sensing peptides that are endowed with the ability to protect bacteria against bacteriophages, form and maintain bacterial communities, and modulate the host immune system. BEVs are potentially promising therapeutic modalities for use in vaccine development, cancer immunotherapy regimens, and drug delivery cargos. Plant-derived EVs (PEVs), such as EVs derived from herbal medicines, can be absorbed by the gut microbiota and influence the composition and homeostasis of gut microbiota. This review highlights the roles of BEVs and PEVs in bacterial and plant physiology and discusses crosstalk among gut bacteria, host metabolism and herbal medicine. In summary, EVs represent crucial communication messengers in the gut microbiota, with potential therapeutic value in the delivery of herbal medicines.

From trash to treasure: the role of bacterial extracellular vesicles in gut health and disease

Bacterial extracellular vesicles (BEVs) have emerged as critical factors involved in gut health regulation, transcending their traditional roles as byproducts of bacterial metabolism. These vesicles function as cargo carriers and contribute to various aspects of intestinal homeostasis, including microbial balance, antimicrobial peptide secretion, physical barrier integrity, and immune system activation. Therefore, any imbalance in BEV production can cause several gut-related issues including intestinal infection, inflammatory bowel disease, metabolic dysregulation, and even cancer. BEVs derived from beneficial or commensal bacteria can act as potent immune regulators and have been implicated in maintaining gut health. They also show promise for future clinical applications in vaccine development and tumor immunotherapy. This review examines the multifaceted role of BEVs in gut health and disease, and also delves into future research directions and potential applications.

Towards the diversification of lactococcal starter and non-starter species in mesophilic dairy culture systems

Lactococcus is one of the earliest identified fermentative bacterial genera and among its member species, the dairy-associated Lactococcus lactis and Lactococcus cremoris are undoubtedly the best studied. These two species are believed to have evolved from plant-associated lactococci and through genome decay and acquisition of plasmids, have adapted to the dairy niche. The past decade has witnessed a surge of activity in novel lactococcal species identification from insect, plant and animal sources. Currently, 22 Lactococcus species are described and in this review, we summarise the genome characteristics of and phylogenetic relationships among these species. Furthermore, we explore the role of mobile elements including plasmids and bacteriophages in the diversification of lactococcal species. The pace of identification of novel lactococcal species suggests that the number of lactococcal species is likely to continue to grow. With additional sequence data for the emerging species, it will be possible to perform pathogenicity/virulence risk evaluations and generate extensive insights into the niche adaptation strategies through which they have evolved.

Shedding Light on the Cell Biology of Platelet-Derived Extracellular Vesicles and Their Biomedical Applications

EVs are membranous subcellular structures originating from various cells, including platelets which consist of biomolecules that can modify the target cell's pathophysiological functions including inflammation, cell communication, coagulation, and metastasis. EVs, which are known to allow the transmission of a wide range of molecules between cells, are gaining popularity in the fields of subcellular treatment, regenerative medicine, and drug delivery. PEVs are the most abundant EVs in circulation, being produced by platelet activation, and are considered to have a significant role in coagulation. PEV cargo is extremely diverse, containing lipids, proteins, nucleic acids, and organelles depending on the condition that induced their release and can regulate a wide range of biological activities. PEVs, unlike platelets, can overcome tissue barriers, allowing platelet-derived contents to be transferred to target cells and organs that platelets cannot reach. Their isolation, characterization, and therapeutic efficacy, on the other hand, are poorly understood. This review summarizes the technical elements of PEV isolation and characterization methods as well as the pathophysiological role of PEVs, including therapeutic potential and translational possibility in diverse disciplines.

Deinococcus radiodurans-derived membrane vesicles protect HaCaT cells against H2O2-induced oxidative stress via modulation of MAPK and Nrf2/ARE pathways

BACKGROUND

Deinococcus radiodurans is a robust bacterium that can withstand harsh environments that cause oxidative stress to macromolecules due to its cellular structure and physiological functions. Cells release extracellular vesicles for intercellular communication and the transfer of biological information; their payload reflects the status of the source cells. Yet, the biological role and mechanism of Deinococcus radiodurans-derived extracellular vesicles remain unclear.

AIM

This study investigated the protective effects of membrane vesicles derived from D. radiodurans (R1-MVs) against H₂O₂-induced oxidative stress in HaCaT cells.

RESULTS

R1-MVs were identified as 322 nm spherical molecules. Pretreatment with R1-MVs inhibited H₂O₂-mediated apoptosis in HaCaT cells by suppressing the loss of mitochondrial membrane potential and reactive oxygen species (ROS) production. R1-MVs increased the superoxide dismutase (SOD) and catalase (CAT) activities, restored glutathione (GSH) homeostasis, and reduced malondialdehyde (MDA) production in H₂O₂-exposed HaCaT cells. Moreover, the protective effect of R1-MVs against H₂O₂-induced oxidative stress in HaCaT cells was dependent on the downregulation of mitogen-activated protein kinase (MAPK) phosphorylation and the upregulation of the nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway. Furthermore, the weaker protective capabilities of R1-MVs derived from ΔDR2577 mutant than that of the wild-type R1-MVs confirmed our inferences and indicated that SlpA protein plays a crucial role in R1-MVs against H₂O₂-induced oxidative stress.

CONCLUSION

Taken together, R1-MVs exert significant protective effects against H₂O₂-induced oxidative stress in keratinocytes and have the potential to be applied in radiation-induced oxidative stress models.

Bacterial clearance and anti-inflammatory effect of Withaferin A against human pathogen of Staphylococcus aureus in infected zebrafish

The emergence of antibiotic resistance is the most challenging factor for developing a proper drug to treat S. aureus infection. These bacterial pathogens can survive in fresh water and spread to various environments. Plant sources, especially pure compounds, are the material of interest amongst researchers for developing drugs of therapeutic value. Here, we report the bacterial clearance and anti-inflammatory potential of the plant compound Withaferin A, using the zebrafish infection model. The minimum inhibitory concentration of the Withaferin A was calculated as 80 µM against S. aureus. The DAPI/PI staining and scanning electron microscopy analysis showed the pore-forming mechanism of Withaferin A on the bacterial membrane. Along with the antibacterial activity, the results from the tube adherence test reveal the antibiofilm property of Withaferin A. In vivo studies were demonstrated to determine the effect of Withaferin A on survival, inflammatory response and behavioural changes during S. aureus infection. Staining zebrafish larvae with neutral red and Sudan black indicates a substantial decrease in the number of localized macrophages and neutrophils. The gene expression analysis showed the downregulation of inflammatory marker genes. Additionally, we observed the improvement in locomotory behaviour among Withaferin A treatment adult zebrafish. In conclusion, S. aureus can infect zebrafish and induces toxicological effect. In comparison, the results from in vitro and in vivo experiments suggest that Withaferin A can be used for synergistic antibacterial, antibiofilm and anti-inflammatory activity to treat infections due S. aureus.

Lactobacillus maintains IFNγ homeostasis to promote behavioral stress resilience

The gut microbiome consists of the trillions of bacteria, fungi, and viruses that inhabit the digestive tract. These communities are sensitive to disruption from environmental exposures ranging from diet changes to illness. Disruption of the community of lactic acid producing bacteria, Lactobaccillacea , has been well documented in mood disorders and stress exposure. In fact, oral supplement with many Lactobacillus species can ameliorate these effects, preventing depression- and anxiety-like behavior. Here, for the first time, we utilize a gnotobiotic mouse colonized with the Altered Schaedler Flora to remove the two native species of Lactobaccillacea . Using this novel microbial community, we found that the Lactobacillus species themselves, and not the disrupted microbial communities are protective from environmental stressors. Further, we determine that Lactobaccillacea are maintaining homeostatic IFNγ levels which are mediating these behavioral and circuit level responses. By utilizing the Altered Schaedler Flora, we have gained new insight into how probiotics influence behavior and give novel methods to study potential therapies developed to treat mood disorders.

Bacterial Extracellular Vesicles: A Candidate Molecule for the Diagnosis and Treatment of Allergic Diseases

Extracellular vesicles (EVs) are an end product released from almost all living cells such as eukaryotic cells and bacteria. These membrane vesicles containing proteins, lipids, and nucleic acids are mainly involved in intracellular communications through the transfer of their components from donor to acceptor cells. Moreover, EVs have been implicated in many functions in response to environmental changes, contributing to health and disease; bacterial EVs depending on their specific parental bacterium have diverse effects on immune responses to play a beneficial or pathogenic role in patients with various allergic and immunologic diseases. As bacterial EVs are a completely new area of investigation in this field, we highlight our current understanding of bacterial EVs and discuss their diagnostic and therapeutic potentials (as immunomodulators) for targeting asthma and atopic dermatitis.

Emerging role of bacterial outer membrane vesicle in gastrointestinal tract

Bacteria form a highly complex ecosystem in the gastrointestinal (GI) tract. In recent years, mounting evidence has shown that bacteria can release nanoscale phospholipid bilayer particles that encapsulate nucleic acids, proteins, lipids, and other molecules. Extracellular vesicles (EVs) are secreted by microorganisms and can transport a variety of important factors, such as virulence factors, antibiotics, HGT, and defensive factors produced by host eukaryotic cells. In addition, these EVs are vital in facilitating communication between microbiota and the host. Therefore, bacterial EVs play a crucial role in maintaining the GI tract's health and proper functioning. In this review, we outlined the structure and composition of bacterial EVs. Additionally, we highlighted the critical role that bacterial EVs play in immune regulation and in maintaining the balance of the gut microbiota. To further elucidate progress in the field of intestinal research and to provide a reference for future EV studies, we also discussed the clinical and pharmacological potential of bacterial EVs, as well as the necessary efforts required to understand the mechanisms of interaction between bacterial EVs and gut pathogenesis.

Dietary-Derived Exosome-like Nanoparticles as Bacterial Modulators: Beyond MicroRNAs

There is increasing evidence that food is an important factor that influences the composition of the gut microbiota. Usually, all the attention has been focused on nutrients such as lipids, proteins, vitamins, or polyphenols. However, a pivotal role in these processes has been linked to dietary-derived exosome-like nanoparticles (DELNs). While food macro- and micronutrient composition are largely well established, there is considerable interest in these DELNs and their cargoes. In this sense, traditionally, all the attention was focused on the proteins or miRNAs contained in these vesicles. However, it has been shown that DELNs would also carry other bioactive molecules with a key role in regulating biochemical pathways and/or interactions with the host's gut microbiome affecting intracellular communication. Due to the scarce literature, it is necessary to compile the current knowledge about the antimicrobial capacity of DELNs and its possible molecular mechanisms that will serve as a starting point. For this reason, in this review, we highlight the impact of DENLs on different bacteria species modulating the host gut microbiota or antibacterial properties. It could be concluded that DELNs, isolated from both plant and animal foods, exert gut microbiota modulation. However, the presence of miRNA in the vesicle cargoes is not the only one responsible for this effect. Lipids present in the DELNs membrane or small molecules packed in may also be responsible for apoptosis signaling, inhibition, or growth promoters.

The role of bacterial membrane vesicles in antibiotic resistance

Bacterial survival during antibiotic exposure is a complex and multifaceted phenomenon. On top of antibiotic resistance genes, biofilm formation, and persister tolerance, bacterial membrane vesicles (MVs) provide a layer of protection that has been largely overlooked. MVs are spherical nanoparticles composed of lipid membranes and are common to Gram-positive and Gram-negative bacteria. Although the importance of MVs in bacterial pathogenesis and virulence factor transport has been firmly established, a growing body of work now identifies MVs as key contributors to bacterial survival during antibiotic exposure. Herein, we highlight the ability of MVs to reduce antibiotic efficacy and transmit resistance elements. We also discuss the potential of targeting MV production as an unconventional therapeutic approach.

Bioinformatic and experimental methods to identify and validate bacterial RNA-human RNA interactions

Ample evidence supports the importance of the microbiota on human health and disease. Recent studies suggest that extracellular vesicles are an important means of bacterial-host communication, in part via the transport of small RNAs (sRNAs). Bacterial sRNAs have been shown to co-precipitate with human and mouse RNA-induced silencing complex, hinting that some may regulate gene expression as eukaryotic microRNAs do. Bioinformatic tools, including those that can incorporate an sRNA's secondary structure, can be used to predict interactions between bacterial sRNAs and human messenger RNAs (mRNAs). Validation of these potential interactions using reproducible experimental methods is essential to move the field forward. This review will cover the evidence of interspecies communication via sRNAs, bioinformatic tools currently available to identify potential bacterial sRNA-host (specifically, human) mRNA interactions, and experimental methods to identify and validate those interactions.