Search Results (217)

Succinimide additives play an important role in combating engine deposits and are therefore commonly blended in fuels. As many of the methods currently used to quantify them in fuel rely on time-consuming techniques and the use of expensive laboratory equipment, a more practical approach was explored. For this purpose, an existing method for aqueous samples involving a colour reaction with Rose Bengal dye and spectrophotometric detection in the UV/Vis range was modified for usage in the nonpolar fuel matrix and tested for applicability. The result was an accessible method for determining the succinimide additive content of diesel fuel—including biodiesel—that is easy to implement in the laboratory routine. Full article

Klebsiella oxytoca has emerged as an important opportunistic pathogen in nosocomial infections, particularly during the COVID-19 pandemic, due to its capacity to acquire and disseminate resistance and virulence genes through horizontal gene transfer (HGT). This study presents a genome-based comparative analysis of K. oxytoca within the genus Klebsiella, aimed at exploring the evolutionary plausibility of outer membrane vesicle (OMV) associated processes in bacterial adaptation. Using publicly available reference genomes, we analyzed pangenome structure, phylogenetic relationships, and the distribution of mobile genetic elements, resistance determinants, virulence factors, and genes related to OMV biogenesis. Our results reveal a conserved set of envelope associated and stress responsive genes involved in vesiculogenic pathways, together with an extensive mobilome and resistome characteristic of the genus. Although these genomic features are consistent with conditions that may favor OMV production, they do not constitute direct evidence of functional OMV mediated horizontal gene transfer. Instead, our findings support a hypothesis generating evolutionary framework in which OMVs may act as a complementary mechanism to established gene transfer routes, including conjugation, integrative mobile elements, and bacteriophages. Overall, this study provides a genomic framework for future experimental and metagenomic investigations into the role of OMV-associated processes in antimicrobial resistance dissemination and should be interpreted as a recently identified evolutionary strategy inferred from genomic data, rather than a novel or experimentally validated mechanism. Full article

Porphyromonas gingivalis (Pg), a keystone pathogen of chronic periodontitis, releases outer membrane vesicles (OMVs) that act as nanoscale vehicles to disseminate virulence factors within periodontal tissues and systemically beyond the oral cavity. Although Pg-OMVs are increasingly recognized as critical mediators of host–pathogen interactions, their effects on the differentiation and function of monocyte–macrophage/osteoclast lineage cells remain unclear. Here, we examined the impact of Pg-OMVs on the differentiation of RAW264.7 monocyte/macrophage-like cells into osteoclasts (OC) and/or macrophages (MΦ) in the presence of receptor activator of nuclear factor-κB ligand (RANKL). OMVs were isolated from Pg W83 and applied to RANKL-primed RAW264.7 cells using three distinct stimulation schedules: (1) simultaneous treatment with Pg-OMVs and RANKL at Day 0; (2) RANKL priming at Day 0 followed by Pg-OMV stimulation at Day 1; and (3) RANKL priming at Day 0 followed by Pg-OMV stimulation at Day 3. In all schedules, cells were cultured for 7 days from the initial RANKL exposure. Remarkably, simultaneous exposure to Pg-OMVs and RANKL (Schedule 1) markedly suppressed osteoclastogenesis (OC-genesis) while promoting M1 macrophage polarization. In contrast, delayed Pg-OMV stimulation of RANKL-primed cells (Schedules 2 and 3) significantly enhanced OC-genesis while reducing M1 polarization. These schedule-dependent effects were consistent with altered expression of osteoclastogenic markers, including dc-stamp, oc-stamp, nfatc1, and acp5. Importantly, a monoclonal antibody against OC-STAMP counteracted the Pg-OMV-induced upregulation of OC-genesis in Schedules 2 and 3. Furthermore, levels of Pg-OMV phagocytosis were inversely correlated with osteoclast formation. Finally, co-stimulation with RANKL and Pg-OMVs (Schedule 1) enhanced macrophage migratory capacity, whereas delayed stimulation with Pg-OMVs (Schedules 2 and 3) did not. Collectively, these findings indicate that Pg-OMVs exert stage-specific effects on the OC/MΦ lineage: stimulation at early stages of RANKL priming suppresses OC-genesis and promotes M1 polarization, whereas stimulation at later stages enhances OC-genesis without inducing M1 differentiation. Thus, Pg-OMVs may critically influence the fate of the OC/MΦ unit in periodontal lesions, contributing to disease progression and tissue destruction. Full article

Porphyromonas gingivalis plays a key role in periodontal disease and has been associated with several serious systemic diseases. Its fimbriae are a major virulence factor. We recently demonstrated the formation of bundles of long FimA fimbriae in strain ATCC 33277. Transmission (TEM) and scanning electron microscopy (SEM) were used to examine a collection of P. gingivalis strains representing all seven known FimA types (I, Ib, IIa, IIb, III–V) and a P. gulae strain (type A). Additionally, two P. gingivalis strains (ATCC 49417 and OMI 1127) were investigated in dual-species approaches together with Fusobacterium nucleatum or Streptococcus oralis as well as in co-culture with human gingival fibroblasts (HGFs). To evaluate the role of fimbriae accessory proteins FimCDE, proteomic analysis of outer membrane vesicles (OMVs) was performed. Bundling was confirmed to occur regardless of FimA type but was impaired by strong capsule formation. Furthermore, tubular and chain-like outer membrane extensions (OMEs) were identified in most strains examined, including P. gulae. For the first time, fimbriae-associated OMVs (FAVs) were observed. REM images suggest that bundled fimbriae, OMEs and FAVs form connections with F. nucleatum and S. oralis. Proteome analysis of OMV content revealed the ratios of FimA to accessory proteins to be approximately 13:1 for FimC and FimD and approximately 7:1 for FimE. The results imply more accessory proteins per fimbriae or shorter FimA fimbriae in OMVs than in cells. Since FimCDE are known to be responsible for the adhesion properties and autoaggregation of FimA fimbriae, we propose that they could also mediate the stability of bundled fimbriae and the binding of OMVs. Full article

The global incidence of multidrug-resistant (MDR) ESKAPE pathogens—comprising Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species—has surged alarmingly in recent years, posing a significant challenge to healthcare systems worldwide. These organisms are notorious for their capacity to evade the effects of multiple classes of antibiotics, leading to treatment failures, increased morbidity and mortality, and escalating healthcare costs, all of which have placed unprecedented strain on existing infection control measures. This review encapsulates the progress in target-driven vaccine research, including the genomic discovery of highly conserved surface antigens, iron acquisition systems, biofilm- and quorum-sensing-related proteins, and computationally predicted epitopes, which are considered the most attractive targets for broad-spectrum vaccination. Novel vaccine platforms, such as outer membrane vesicles (OMVs), mRNA technologies, and multi-epitope constructs, will rapidly drive the translation of these targets into next-generation vaccine formulations. Nevertheless, challenges such as antigenic variation and immune evasion, as well as the need for a robust mucosal and cross-protective immune response, persist. The sustainability in interdisciplinary investigations are required, along with adjunctive measures and investment in the development of advanced discovery and delivery systems, to achieve the ultimate goal of successful vaccines against MDR ESKAPE infections and to mitigate the worldwide burden of antimicrobial resistance. Full article

Poultry serve as natural reservoirs for Salmonella spp., and the consumption of Salmonella-contaminated poultry products remains a leading cause of infection in both developed and developing countries. The irrational use of antimicrobials in the poultry industry has contributed to the global emergence of multidrug-resistant (MDR) Salmonella strains. This study aimed to evaluate whether Salmonella enterica serovar Typhimurium (S. typhimurium) outer membrane vesicles (OMVs) could serve as a broad-spectrum immunogen, providing protection against the most prevalent MDR Salmonella serovars. The immunogenicity and protective efficacy of S. typhimurium OMVs were assessed in both specific-pathogen-free (SPF) mice and chickens challenged with S. typhimurium infection. In addition, the cross-protective efficacy of OMVs against infections with heterologous serovars, specifically S. montevideo and S. albany, was also evaluated in chickens. Our results demonstrated that S. typhimurium OMVs elicited a robust humoral immune response and conferred significant immune protection in both mice and chickens. Following challenges with MDR S. montevideo and S. albany strains, immunized birds exhibited reduced levels of fecal shedding and liver invasion. Furthermore, in vitro studies revealed that S. typhimurium OMVs also possess cross-immunogenicity against MDR S. Enteritidis and S. gallinarum. In conclusion, S. typhimurium OMVs provide cross-protection against heterologous MDR Salmonella infections both in vitro and in vivo. Our study suggests that OMVs derived from S. typhimurium strains hold promise as novel subunit vaccine candidates for preventing MDR heterologous serovar infections in animals, offering a potential solution to the growing challenge of antimicrobial resistance in the poultry industry. Full article

Klebsiella pneumoniae (K. pneumoniae) is an opportunistic bacteria that can result in severe liver abscesses, pulmonary damage, and potentially fatal outcomes. Research has demonstrated that the outer membrane vesicles (OMVs) released by it can provide significant protection to infected animals and may serve as a promising candidate antigen for the development of a novel vaccine. Nevertheless, the specific mechanisms through which OMVs mitigate the detrimental effects of K. pneumoniae infection by promoting the polarization pathways of macrophages and T helper cells (Th cells) remain poorly understood. In this study, we first confirmed that Klebsiella pneumoniae outer membrane vesicles (K. pneumoniae_OMVs) were protective in K. pneumoniae-infected mice, and then we investigated the protective mechanisms by transcriptome data analysis. Then, we constructed a model of in vitro macrophage polarization, an in vivo model for Th differentiation, and a K. pneumoniae infection model in K. pneumoniae_OMVs-immunized mice. qRT-PCR, IHC, Western blotting, and ELISA were used to confirm the polarization indicators. The results showed that K. pneumoniae_OMVs were able to provide specific protection for mice with a maximum protection rate of 80%. In addition, the results of a transcriptome analysis suggested that the protective mechanism might be related to Th cells and macrophage polarization. Mice immunized with K. pneumoniae_OMVs were able to achieve rapid bacterial clearance after K. pneumoniae infection through an M1/Th1 immune response. Subsequently, tissue repair was accomplished through Th2/M2 immune response in the late stage of K. pneumoniae infection to avoid causing inflammatory damage. This study offers a theoretical foundation for the K. pneumoniae_OMVs vaccine’s actual application. Full article

For over eight decades, antibiotics have been the cornerstone of treating bacterial infections. However, the rapid rise of antibiotic-resistant pathogens has created an urgent need for alternative therapeutic strategies. Advances in nanotechnology offer a promising solution through the development of bio-derived nanoparticles. This broad class includes extracellular vesicles such as exosomes and bacterial outer membrane vesicles (OMVs), as well as bioengineered cell membrane-coated nanoparticles (CMNPs) that combine synthetic cores with natural membranes from diverse source cells. These particles possess unique physicochemical and biological properties, such as intrinsic bioactivity, biocompatibility, and structural versatility, that can be harnessed for antimicrobial therapy. This review synthesizes recent progress in the design, characterization, and application of biological nanoparticles for combating bacterial infections. We place particular emphasis on their mechanisms of action, therapeutic potential, and key research directions that could accelerate their translation into clinical use. Full article

Extracellular vesicles, encompassing eukaryotic exosomes and bacterial outer membrane vesicles (OMVs), play multifaceted roles in mediating host–pathogen interactions. These nanoscale structures act as critical mediators of intercellular communication, transporting diverse bioactive cargo such as miRNAs, cytokines, proteins, and bacterial components. Exosomes contribute to host immunity by delivering antimicrobial agents and modulating inflammatory responses, but they can also be hijacked by pathogens to suppress defenses and promote persistent infection. OMVs, on the other hand, enable bacteria to disseminate virulence factors, deliver toxins directly into host cells, and modulate immune signaling. For example, exosomes from infected macrophages can stimulate dendritic cell activation and T-cell priming, whereas bacterial OMVs have been shown to suppress host immunity or trigger excessive inflammation depending on their molecular cargo. Importantly, OMVs facilitate horizontal gene transfer and nutrient exchange within microbial communities, thereby influencing microbiome composition and adaptation. Together, these complex dynamics position both exosomes and OMVs as central players in immunity and pathogenesis. This review synthesizes recent insights into how host- and pathogen-derived vesicles modulate infection biology and immune responses, while also exploring their potential as diagnostic biomarkers and therapeutic carriers, and discussing current limitations in their clinical translation. Full article

Mytilus coruscus, a commercially important mariculture mussel in China, has shown a marked decline in larval settlement and metamorphosis over the past decade, a trend often linked to environmental degradation and resource depletion. Numerous studies have identified bacterial biofilms as key modulators of mussel larval settlement. To investigate this, we deployed PVC plates in situ within aquaculture zones near Shengsi (Zhoushan, Zhejiang) and Lianjiang (Fuzhou, Fujian). After natural biofilm colonization on the plates, juvenile M. coruscus were introduced to assess settlement rates. The attached juveniles were homogenized, leading to the isolation of four dominant bacterial strains: Pseudomonas sp. LJBF001, Vibrio sp. LJBF002, Pseudomonas sp. LJBF003 and Bacillus sp. LJBF004. Compared to control PVC plates, natural biofilms significantly promoted juvenile settlement, with the Lianjiang (LJ) group reaching up to >29% under our assay conditions. In contrast, monospecific biofilms prepared from these isolates did not significantly increase larval metamorphosis; the numerically highest response (LJBF004) reached ~9% and was not significant versus the control. These contrasting outcomes are consistent with a threshold–multi-cue synergy mechanism, whereby cue diversity and partial redundancy in natural biofilms favour threshold crossing, while restricted cue sets in single-strain films often fall short. Guided by this framework, priority next steps include testing c-di-GMP delivery (soluble and via OMVs), probing EPS structure–function and EPS–OMV/LPS–free-fatty-acid blends alongside minimal multi-strain consortia, and adopting stage-gated assays with time-to-event endpoints and effect-size/CI reporting. Full article

This study evaluates the technical and economic feasibility of liquid polymer emulsions as substitutes for powder polymers in polymer flooding applications, particularly in space-constrained, low-permeability reservoirs in Austria. Rheological tests determined that target viscosities of 20 mPa·s at 20 °C and a shear rate of 7.94 s⁻¹ were achieved using concentrations of 1200 ppm for liquid polymer 1 (LP1), 2250 ppm for liquid polymer 2 (LP2), and 1200–1400 ppm for powder polymers. Injectivity tests revealed that liquid polymers encountered challenges in 60 mD and 300 mD core plugs, with pressure stabilization not achieved at injection rates of 1–2.5 ft/day. Powder polymers demonstrated stable injectivity, with powder polymer 1 (PP1) showing an optimal performance at 10 ft/day and a low residual resistance factor (RRF). Two-phase core floods using PP1 and powder polymer 2 (PP2) at 1 ft/day yielded incremental oil recovery factors of approximately 5%, with a maximum of 8% observed for higher viscosity slugs. Economic analysis indicated that over a 3-year horizon, liquid polymers are 30% cheaper than powder polymer Option 1 but 100% more expensive than Option 2. Over a 10-year horizon, liquid polymers are 50% more expensive than both powder polymer options. Although liquid polymers offer logistical advantages, they are unsuitable for low-permeability reservoirs. Powdered polymers, particularly PP1, are recommended for pilot implementation due to superior injectivity, mechanical stability, and recovery performance. Full article

The global rise of antimicrobial resistance represents a critical challenge to public health, with Escherichia coli emerging as one of the most significant contributors due to its high adaptability and prevalence of extended-spectrum β-lactamase (ESBL) production. Outer membrane vesicles (OMVs), nanoscale structures released by Gram-negative bacteria, have recently been implicated in the dissemination of resistance determinants and direct antibiotic inactivation. This study investigated the role of OMVs derived from ESBL-producing E. coli in mediating resistance to ampicillin. Clinical strains harboring CTX-M-15 resistance genes were cultured under selective pressure, and OMVs were purified via size-exclusion chromatography. Characterization using tunable resistive pulse sensing (TRPS) and cryo-transmission electron microscopy confirmed vesicle integrity, with sizes ranging from 80 to 150 nm. DNA quantification and PCR analysis revealed the presence of CTX-M-15 genes within vesicles, which remained protected from DNase digestion, confirming encapsulation. Functional assays demonstrated β-lactamase activity within OMVs, with proteinase K treatment indicating localization primarily within vesicles rather than on their surface. Importantly, OMVs inactivated ampicillin in a dose-dependent manner, significantly reducing its efficacy against susceptible E. coli. Disc diffusion and microtiter plate assays confirmed that β-lactamase-positive OMVs protected susceptible strains from antibiotic killing, promoting bacterial survival and growth. This study uniquely demonstrates that OMVs from CTX-M-15–producing Escherichia coli carry both resistance genes and active β-lactamase enzymes, thereby facilitating both genetic dissemination and direct antibiotic inactivation. Targeting OMV biogenesis may represent a novel strategy to combat antimicrobial resistance. Full article

Background: Borrelia burgdorferi, the causative agent of Lyme disease, releases outer membrane vesicles (OMVs) that may contribute to infection and modulate the host immune response. Although interest in OMVs is growing, few studies have systematically compared methods for isolating OMVs from B. burgdorferi. Methods: In this study, we evaluated two OMV isolation techniques—standard ultracentrifugation and an ion-exchange chromatography-based ExoBacteria™ kit—and examined how serum supplements (rabbit serum vs. exosome-depleted fetal bovine serum, ED-FBS) influence Bb-OMV yield and composition. Gene expression profiles were assessed using RT-PCR, and specific protein content was identified by Western blot analyses. To assess the ability of Bb-OMVs to interact with host cells, Bb-OMVs were co-cultured with MDA-MB-231 triple-negative breast cancer cells. Results: Transmission electron microscopy confirmed that both methods produced spherical Bb-OMVs with intact membrane bilayers. Ultracentrifugation generated larger vesicles (15–180 nm), while the ExoBacteria™ kit yielded smaller vesicles (<50 nm) with a higher double-stranded DNA (dsDNA) content, and protein levels were similar across samples. Cultures grown with rabbit serum produced more Bb-OMVs and had cleaner backgrounds in the TEM images than those grown with ED-FBS. All Bb-OMV samples lacked intracellular markers (DnaK and 16S rRNA) and consistently expressed the outer surface protein OspA, confirming high purity. All isolated Bb-OMVs were taken up by the cells, as indicated by OspA expression, without detectable 16S rRNA, confirming vesicle internalization without bacterial contamination. Conclusions: These findings indicate that isolated OMVs are biologically active and capable of interacting with mammalian cells, highlighting their potential role in host–pathogen interactions and the broader relevance of OMVs in studying bacterial modulation of mammalian cell behavior. Overall, both isolation methods produced high-quality OMVs, with ultracentrifugation yielding slightly more pure vesicles, emphasizing the importance of selecting appropriate isolation methods and culture conditions for functional OMV studies. Full article

Bacterial outer-membrane vesicles (OMVs) mediate stress tolerance, biofilm formation, and interkingdom communication, but their role in beneficial endophytes remains underexplored. We isolated 11 non-redundant isolates associated with Bacillus, Enterococcus, Kosakonia and Kocuria from Agave tequilana seeds, identified by MALDI-TOF MS and 16S rRNA gene sequencing. We focused on the catalase-negative Enterobacter cloacae SEA01, which exhibits plant-promoting traits and support agave growth under nutrient-poor microcosms. In addition, this endophyte produces OMVs. Time-resolved SEM documented OMV release and cell aggregation within 9 h, followed by mature biofilms at 24 h with continued vesiculation. Purified OMVs (≈80–300 nm) contained extracellular DNA and were characterized by dynamic light scattering and UHPLC–ESI–QTOF-MS lipidomics. The OMV lipidome was dominated by phosphatidylethanolamine (~80%) and was enriched in monounsaturated fatty acids (16:1, 18:1), while the stress-associated cyclopropane fatty acids (17:1, 19:1) were comparatively retained in the whole-cell membranes; OMVs also exhibited reduced ubiquinone-8. SEA01 is catalase-negative, uncommon among plant-associated Enterobacter, suggesting a testable model in which oxidative factors modulate OMV output and biofilm assembly. These may have implications for recognition and redox signaling at the root interface. Future works should combine targeted proteomics/genomics with genetic or chemical disruption of catalase/OMV pathways. Full article

Chronic infection with Helicobacter pylori is the leading environmental cause of gastric carcinogenesis, yet the molecular pathways remain incompletely defined. This review links H. pylori-derived outer membrane vesicles (OMVs) and host epithelial exosomes through their shared cargo of heat shock protein 60 (GroEL/Hsp60). We proposed the concept of the “muco-microbiotic layer” as a fifth, functionally distinct layer of the gastric wall, where bacterial and host extracellular vesicles (EVs) interact within the mucus–microbiota interface. In this compartment, OMVs carrying bacterial GroEL and exosomes containing human Hsp60 engage in bidirectional communication that may promote chronic inflammation and epithelial transformation, with putative participation of molecular mimicry. The high structural homology between microbial and human Hsp60 enables repeated immune exposure to trigger cross-reactive responses—potentially leading to autoimmune-driven tissue damage, immune tolerance, and immune evasion in pre-neoplastic lesions. This vesicular crosstalk aligns with the evolution from non-atrophic gastritis to atrophy, from intestinal metaplasia to dysplasia, and lastly adenocarcinoma. Therapeutically, targeting EV-mediated Hsp60/GroEL signaling might offer promising strategies: EV-based biomarkers for early detection, monoclonal antibodies against extracellular Hsp60/GroEL, modulation of vesicle release, and probiotic-derived nanovesicles to restore mucosal balance. Hence, recognizing the muco-microbiotic layer and its vesicle-mediated signaling provides a new framework for understanding the infection–inflammation–cancer axis and for developing diagnostic and therapeutic approaches in H. pylori-associated gastric cancer. Full article