Frontiers in Microbiology最新文献

Objective: Despite the success of mRNA-LNPs vaccines against viruses, their potential against prokaryotic pathogens remains underexplored. We provide proof-of-concept for an mRNA-LNPs vaccine against Streptococcus mutans (S. mutans), the primary cause of dental caries.

Methods: We constructed LNPs-encapsulated mRNA vaccines encoding S. mutans PAc antigen alone or PAc fused with human IgG Fc domain, aiming to enhance mucosal immunity via Fc-FcRn interactions.

Results: A heterologous intramuscular prime-intranasal boost regimen induced robust, durable (>4 months) sIgA responses-2.6-fold higher with Fc fusion-that significantly inhibited S. mutans biofilm formation in vitro and reduced moderate dentinal caries by >60% in rats.

Conclusion: Bacterial antigens can be effectively delivered via mRNA platforms, and Fc fusion is a promising strategy to enhance mucosal immunity against oral, respiratory, and other mucosal pathogens, consistent with Fc-FcRn-mediated mechanisms.

Porcine reproductive and respiratory syndrome virus (PRRSV) glycoprotein 3 (GP3) forms a heterotrimeric complex with GP2 and GP4, which is essential for viral entry and assembly. However, the intracellular trafficking mechanisms governing GP3 localization and incorporation into virions remain incompletely understood. Here, we identified two highly conserved tyrosine-based sorting signals (YxxΦ) within GP3, motifs that mediate adaptor protein-dependent trafficking through the secretory and endocytic pathways. To define the functional roles of these motifs, we established a Linear Overlapping Infectious Polymerase Amplicon (LOIPA)-based reverse-genetics system for PRRSV. This system enabled precise reconstitution of full-length viral genomes from overlapping cDNA fragments and facilitated rapid introduction of site-specific mutations without bacterial cloning. Using LOIPA, we generated a set of recombinant PRRSV mutants carrying targeted substitutions within the two GP3 YxxΦ motifs. Mutation of Y108A in the YAWL motif at positions 108-111 disrupted GP3 sorting to downstream ER-Golgi intermediate compartments (ERGIC) and markedly reduced infectious virion production. In contrast, mutations in the YVDI motif did not alter GP3 trafficking patterns but exerted limited effects on viral replication, suggesting an indirect regulatory role. Interestingly, the ectopic monomeric expression of GP3-Y108A showed similar trafficking patterns to those of GP3-WT. These results provide novel insights into the molecular interplay between PRRSV envelope proteins and host trafficking machinery, contributing to a deeper understanding of PRRSV assembly, virion morphogenesis, and secretory dynamics. Our study also established LOIPA as a rapid and bacteria-free reverse genetics system for PRRSV, which is readily applicable to other member viruses in the family Arteriviridae, enabling functional interrogation of viral genes and rational engineering to produce mutant viruses.

Introduction: Piglet birth weight is a key determinant of preweaning survival and subsequent growth performance, yet the role of maternal gut microbiota in relation to offspring birth weight in sows remains incompletely characterized. This study aimed to investigate the association between maternal gut microbiota in late gestation and offspring birth weight in sows.

Methods: Fecal samples were collected from 260 Landrace × Yorkshire (LY) sows at gestation day 100, and sows were categorized into high birth weight (HBW; 1.41 ± 0.02 kg, 16.25 ± 0.25 piglets/litter, n = 59) and low birth weight (LBW; 1.07 ± 0.02 kg, 12.19 ± 0.22 piglets/litter, n = 52) groups based on the average birth weight of live-born piglets and live litter size. We performed 16S rRNA gene amplicon sequencing and fecal untargeted metabolomics, and quantified fecal short-chain fatty acids (SCFAs) and sex hormones.

Results: Compared with LBW sows, HBW sows showed distinct bacterial community profiles with higher relative abundances of multiple taxa linked to SCFAs production, including Ruminococcus, Oscillibacter, Parabacteroides, and Bacteroides (p < 0.05). Untargeted metabolomics revealed a clear separation between groups and enrichment of pathways related to primary bile acid biosynthesis and steroid hormone biosynthesis in HBW sows (p < 0.05). Consistently, fecal acetate (p = 0.005), propionate (p = 0.034), isobutyrate (p = 0.007), valerate (p = 0.036), as well as progesterone (p = 0.016), were significantly higher in HBW sows, and these indices were also positively correlated with piglet birth weight. Spearman correlation analysis showed that gut bacterial taxa enriched in the HBW group were positively associated with primary bile acids and sex hormone-related metabolites, which were also positively correlated with piglet birth weight.

Discussion: In conclusion, these multi-omics data indicate that higher piglet birth weight is associated with an SCFAs-enriched gut microbial ecosystem accompanied by enhanced bile acid and steroid hormone-related fecal metabolic profiles during late gestation.

Introduction: The global diabetes epidemic has brought gestational diabetes mellitus (GDM) and its long-term impacts on maternal-child health into sharp focus. Emerging evidence indicates that early-life metabolic programing, mediated significantly by gut microbiota, profoundly influences offspring glucose homeostasis. Notably, microbial-targeted nutritional interventions, including probiotic and prebiotic supplementation, have considerable potential as innovative therapeutic approaches. These strategies may effectively prevent intergenerational transmission of metabolic diseases by improving glucose metabolism in both mother and offspring.

Methods: This narrative review synthesizes evidence from clinical trials and animal studies investigating the effects of maternal probiotic and prebiotic supplementation on glucose metabolism. We searched and analyzed literature focusing on glycemic outcomes in pregnant women with or without GDM and their offspring, as well as studies exploring underlying mechanisms including gut microbiota modulation, metabolite production, inflammatory pathways, and epigenetic regulation.

Results: Clinical and animal studies have shown that probiotics and prebiotics can significantly alleviate metabolic parameters such as elevated fasting glucose and insulin resistance in patients with GDM, but their preventive effect on the incidence of GDM is unclear. In addition, maternal supplementation with probiotics or prebiotics may positively affect glucose metabolism in offspring through multiple interconnected mechanisms, which include the modulation of intestinal microbial ecology, the increased generation of microbial- derived metabolites such as short-chain fatty acids (SCFAs), the mitigation of inflammatory responses, and epigenetic regulation (e.g., DNA methylation, lncRNA and miRNA modification).

Discussion: Despite some heterogeneity in the results of existing studies, there is overall support for the therapeutic potential of probiotic and prebiotic interventions in optimizing metabolic outcomes for both maternal and pediatric populations. Future studies need to further define the optimal type, dose and timing of intervention for probiotics and prebiotics and explore precise intervention strategies on the basis of individual gut microbiota characteristics. In conclusion, probiotic and prebiotic supplementation during pregnancy and lactation may become an adjunctive tool to improve glucose metabolism in mothers and infants, resulting in innovative approaches for the primary prevention of metabolic diseases.

The Type VI Secretion System (T6SS) is a sophisticated, phage-tail-like contractile nanomachine that mediates contact-dependent protein translocation in a wide range of Gram-negative enteric pathogens. As a primary weapon for interference competition, T6SS enables pathogens like Salmonella and Vibrio cholerae to directly eliminate commensal rivals. This targeted elimination allows pathogens to dismantle microbiota-mediated colonization resistance and seize essential nutritional niches. Beyond interbacterial warfare, the system facilitates "exploitative competition" by secreting effectors for the acquisition of limited micronutrients such as iron and zinc. Furthermore, T6SS acts as a crucial virulence determinant by manipulating host cell signaling, disrupting cytoskeletal integrity, and even enhancing intestinal contractions to physically expel competitors. The expression and activity of T6SS are dynamically regulated by gastrointestinal cues, including bile salts, pH fluctuations, and quorum sensing signals, ensuring its activation is precisely timed during infection. Elucidating these multifaceted roles not only deepens our understanding of microbial ecology in the gut but also highlights T6SS as a promising target for microbiome engineering and the development of customizable, precision antimicrobial therapies.

Desulfuromonas acetexigens has gained attention as a biocatalyst in microbial electrolysis cells (MECs) due to its inability to utilize hydrogen as an electron donor, which favors beneficial Coulombic efficiencies (CE). In this study, the electrochemical performance and biofilm morphology of D. acetexigens were compared with the model organism Geobacter sulfurreducens in flow cell MECs. Biofilm morphology was assessed non-invasively via optical coherence tomography (OCT), providing insight into quantitative parameters, including spatially resolved thickness, biovolume and anode surface coverage. While both species achieved similar maximum current densities when cultivated under identical conditions, D. acetexigens biofilms established faster, generating current after ~4 days, whereas G. sulfurreducens exhibited a lag phase of ~8 days. Limitations of extracellular electron transfer already occurred at lower average biofilm volumes for D. acetexigens ( $\left({\overline{BV}}_{\overline{J}\max }\right)$ ≈ 16 ± 6 μm³ μm^-2) than for Geobacter ( ${\overline{BV}}_{\overline{J}max}$ ≈ 40 ± 7 μm³ μm^-2). One monocultural D. acetexigens cultivation revealed a CE of ~96%, consistent with no detectable hydrogen utilization under the tested condition, while some cultivations showed net acetate increases. Phylogenetic analyses of the latter indicated niche dominance of the target EAM despite homoacetogenic and clostridial contaminants. Production of short-chain fatty acids suggested interspecies metabolic interaction and led to the hypothesis of an electrode-mediated ethanol to acetate fermentation by electroactive microorganisms and ethanol-utilizing contaminants such as the homoacetogen Sporomusa sphaeroides.

Background: Coronary heart disease (CHD) is a leading cause of morbidity and mortality worldwide. Increasing evidence indicates that gut microbiota dysbiosis contributes to CHD pathogenesis through metabolic, inflammatory, and coagulation-related mechanisms. However, comprehensive multi-omics investigations of individuals with CHD remain limited. In this study, we aimed to characterize the multi-omics features of CHD and to identify potential diagnostic biomarkers.

Methods: The study included 10 patients with clinically diagnosed CHD and 10 healthy controls. Blood and fecal samples were collected for further analysis. The gut microbiota composition was assessed using 16S ribosomal RNA high-throughput sequencing, and shotgun metagenomic sequencing was further performed to evaluate microbial functional potential through the Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation and differential pathway analysis. Non-targeted metabolomic profiling was performed using ultra-high-performance liquid chromatography coupled with Orbitrap mass spectrometry, and quantitative proteomic analysis was conducted using liquid chromatography-tandem mass spectrometry. Functional interaction networks between differentially expressed metabolites and proteins were constructed using Spearman correlation analysis, and the diagnostic potential of candidate biomarkers was evaluated using receiver operating characteristic (ROC) curve analysis.

Results: At the phylum level, the CHD group exhibited an increased abundance of Pseudomonadota and a decreased abundance of Bacillota and Actinomycetota. At the genus level, Escherichia-Shigella, Bacteroides, and Klebsiella were significantly enriched, whereas Bifidobacterium and Faecalibacterium were decreased in abundance. Shotgun metagenomic analysis revealed functional remodeling of gut microbiota in CHD, with upregulation of KEGG pathways related to energy metabolism, inflammatory signaling, and host-microbe interactions. Serum metabolomics and proteomic analyses identified 32 differentially expressed metabolites and 38 differentially expressed proteins, respectively. Correlation analysis revealed significant associations between phospholipid metabolites and apolipoproteins, inflammatory mediators and the complement system, asymmetric dimethylarginine and endothelial function-related proteins, and oxidative stress metabolites and antioxidant proteins. ROC analysis identified several potential biomarkers with high diagnostic value.

Conclusion: We demonstrate that individuals with CHD exhibit significant gut microbiota dysbiosis, distinct metabolic pathway alterations, and aberrant expression of coagulation- and inflammatory-related proteins. These findings provide novel insights into potential targets for CHD prevention and treatment strategies.

Superoxide is a toxic byproduct of aerobic cellular respiration. The cellular regulation of bacterial responses to superoxide stress remains incompletely understood. The present work established an Escherichia coli cell model for superoxide stress by deleting superoxide dismutase (SOD) SodA and SodB. Proteomic analysis revealed that SOD deficiency not only induced high expression of the oxidative stress regulator SoxSR but also upregulated the catalase KatE and the organic peroxidases Tpx and BtuE, suggesting that SOD deficiency leads to the subsequent production of multiple reactive oxygen species. Further analysis of central carbon metabolism networks showed that SOD deficiency suppressed oxidative phosphorylation, thereby reducing superoxide production. SOD defects stimulated the pentose phosphate pathway (PPP) and its downstream pathways involved in histidine and phenylalanine synthesis, as well as fatty acid degradation pathway. SOD deficiency rendered E. coli more sensitive to the lethal effects of exogenous hydrogen peroxide. CRISPR-mediated deletion of zwf to block PPP, deletion of hisD and pheA to disrupt histidine and phenylalanine synthesis, or deletion of fadE to block fatty acid degradation, all increased the SOD mutant's sensitivity to hydrogen peroxide. The absence of fadE, rather than hisD or pheA, further reduced the survival of zwf-SOD mutant under H₂O₂ killing. These data indicate that the PPP and fatty acid degradation pathways help SOD-deficient cells respond to oxidative stress. Overall, our findings offer new perspectives on bacterial defenses against oxidative stress and survival strategies.