Objective To investigate the effect of Lactobacillus reuteri CCTCC M 2016546 on chronic unpredictable mild stress (CUMS)-induced depression in rats and explore its potential mechanism. Methods Sixty male Sprague-Dawley (SD) rats were initially randomized into three groups: blank control (n=8), CUMS model (n=43), and prevention (n=9). The other groups except the blank control group received three CUMS stimuli daily. The prevention group was administrated with the L. reuteri CCTCC M 2016546 suspension (1×10⁹ CFU/d) via oral gavage prior to daily stress induction. After 4 weeks, depressive behaviors were assessed by sucrose preference, forced swimming, and open field tests. Successfully modeled rats (n=43) were re-randomized into five groups: model control (n=8), fluoxetine (2.1 mg/kg, n=8), combined therapy (2.1 mg/kg fluoxetine+1×10⁹ CFU/d CCTCC M 2016546, n=9), high-dose CCTCC M 2016546 (5×10⁹ CFU/d L. reuteri CCTCC M 2016546, n=9), and low-dose CCTCC M 2016546 (1×10⁹ CFU/d CCTCC M 2016546, n=9). Rats were administrated with corresponding agents daily for 4 weeks and then subjected to behavioral tests again. The levels of 5-hydroxytryptamine (5-HT) in the hippocampus and adrenocorticotropic hormone (ACTH) and cortisol (CORT) in the serum were quantified via ELISA. Western blotting was performed to determine the protein levels of brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor B (TrkB), protein kinase B (Akt), phosphatidylinisitol 3-kinase (PI3K), extracellular signal-regulated kinase (ERK), and cAMP-response element binding protein (CREB) in the brain tissue. Results Compared with the model control group, all treatment modalities (fluoxetine, combined therapy, and CCTCC M 2016546) alleviated depressive behaviors: increasing sucrose preference (P<0.01, P<0.001), reducing immobility time in suspension (P<0.01, P<0.05), and enhancing horizontal locomotion distance/central zone exploration (P<0.01, P<0.05). Biochemical analyses revealed that treatments reversed the CUMS-induced alterations in 5-HT, CORT, and ACTH levels (P<0.01, P<0.05). Western blotting demonstrated upregulated protein levels of BDNF, PI3K, CREB, TrkB, Akt, and ERK in the fluoxetine and combined therapy groups (P<0.01, P<0.05). High-dose CCTCC M 2016546 elevated Akt, BDNF, CREB, and PI3K levels (P<0.01, P<0.05), while low-dose CCTCC M 2016546 raised Akt and BDNF levels (P<0.01). Prophylactic CCTCC M 2016546 administration primarily enhanced TrkB expression (P<0.05). Conclusion L. reuteri CCTCC M 2016546 ameliorates CUMS-induced depression in rats, potentially by modulating the hypothalamic-pituitary-adrenal axis hyperactivity and activating the PI3K/Akt/CREB/BDNF signaling pathway.

The potent antibacterial activity of silver nanoparticles is primarily attributed to the release of silver ions, which disrupt cell membranes and inactivate essential enzymes through Ag-S bonding formation. Objective To explore silver ion immobilization to minimize silver release. Methods A macrocyclic cryptand with nitrogen bridgeheads was prepared and subsequently chelated with silver ions to produce Cage silver(I), which was then coordinated with different ratios of sulfonated chitosan (SCS) to form SCS/Cage Ag(I) complexes (SCA1, SCA2, and SCA3). The antioxidant activities of the complexes were assessed by reducing power and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and hydrogen peroxide scavenging assays. The antibacterial activities of the complexes were evaluated based on the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) against Staphylococcus aureus ATCC 6538 and Escherichia coli O157:H7 and the inhibition rate on biofilm formation. Results Cage silver(I) exhibited strong antibacterial activity, with the MIC of 0.015 mg/mL and MBC of 0.031 mg/mL against S. aureus ATCC 6538, and the MIC of 0.031 mg/mL and MBC of 0.120 mg/mL against E. coli O157:H7. Significant antioxidant properties of Cage silver(I) were also observed, as demonstrated by the DPPH free radical scavenging rates of 42.2% and 53.1% at 326 nm and 517 nm, respectively. Cage silver(I) exhibited the highest antibacterial and antioxidant activities, followed by SCA1, SCA2, SCA3, and SCS, because the content of silver ions in Cage silver(I) was 10-fold higher than that in SCA1. The antibacterial and antioxidant activities of SCA1 were better than those of Cage silver(I), which further indicated that the sulfonic groups of SCS may intensely coordinate with silver ions to exert synergistic effects. Conclusion Combining the merits of silver ions and SCS improves the bioavailability of the agent at microbicidal concentrations, minimizes the accumulation in the environment, and reduces treatment costs. The method developed herein offers a sustainable approach to enhance microbial control while minimizing the impact on the environment.

Myosmine, also known as 3-(3,4-dihydro-2H-pyrrol-5-yl) pyridine, is a tobacco alkaloid found not only in tobacco but also in various foods, fruits, and vegetables. It serves as one of the precursors for the formation of the carcinogenic tobacco-specific nitrosamine N′-nitrosonornicotine, posing a potential threat to human health. Objective To screen bacterial strains capable of degrading myosmine and preliminarily explore the pathways and mechanisms underlying myosmine degradation. Methods We used myosmine as the sole carbon source to enrich and isolate the myosmine-degrading bacterial strain from tobacco-growing soil. Taxonomic identification of this myosmine-degrading strain was achieved by a combination of morphological observation, physiological and biochemical testing, and molecular analysis. The myosmine degradation products by this strain were analyzed by HPLC and UHPLC-MS/MS. The degradation genes were predicted by BLAST comparison. Results A strain G-2 capable of degrading myosmine was successfully isolated. The strain was identified as a member of Shinella, designated Shinella sp. G-2. HPLC and UHPLC-MS/MS identified five degradation products. Genomic analysis showed that strain G-2 possessed a homologous gene cluster of a variant of the pyridine and pyrrolidine pathway (VPP) gene cluster. Conclusion In this study, a strain Shinella sp. G-2 with the ability to degrade myosmine was isolated. Strain G-2 might use enzymes in the VPP pathway to degrade myosmine through a metabolic pathway similar to the VPP pathway.

Objective To analyze the activity of ribose-5-phosphate isomerase B (RpiB) encoded by lmo0736 and explore its effect on the infection of Listeria monocytogenes (LM). Methods The recombinant protein Lmo0736 was obtained by prokaryotic expression and purification, and its catalytic activity for substrates was verified by the enzyme activity assay. The LM strain with lmo0736 knockout (LM Δlmo0736) and the complementary strain (LM CΔlmo0736) were constructed by bacterial homologous recombination. The growth curves of bacteria in vitro were plotted. The adhesion, invasion, and intercellular migration of bacteria were evaluated by in vitro cell infection models (Caco-2 intestinal epithelial cells and L929 fibroblasts). The ICR mouse infection model was used to measure the 7 d survival rate and 48 h organ load of each strain, and thus the pathogenicity of strains in mice was evaluated. Results Lmo0736 had typical RpiB activity and catalyzed the conversion of d-ribose-5-phosphate to d-ribulose-5-phosphate, with V_max=0.366 mmol/(L·min), K_m=4.489 mmol/L, k_cat=12.300 s^-1, and k_cat/K_m=2.740 L/(mmol·s). The growth rate of LM Δlmo0736 was not significantly different from that of the wild type EGD-e and LM CΔlmo0736in vitro, indicating that the deletion of lmo0736 did not affect the basic growth of bacteria. LM Δlmo0736 demonstrated significantly decreased adhesion and invasion in Caco-2 cells and intercellular migration in L929 cells and weakened colonization in mice, which indicated that lmo0736 regulated the pathogenicity of LM through a RpiB-dependent metabolic pathway. Conclusion This study reveals for the first time that the Lmo0736 of LM has typical RpiB activity. Although the functional loss of Lmo0736 does not directly affect the basic growth of the bacteria, it significantly attenuates the pathogenicity by weakening the adhesion, invasion, and intracellular migration in host cells and the colonization in vivo. The results accumulate experimental data for in-depth exploration of the biological functions of RpiB in LM. From the perspective of the association between metabolism and virulence, this study provides an experimental basis for delving into the infection mechanism of foodborne pathogens.

Objective To identify the species and investigate the diversity of 120 Burkholderia cepacia complex (Bcc) strains isolated from industrial products and their production environments between 2022 and 2023. Additionally, the whole genome of a novel sequence type (ST) strain, Burkholderia aenigmatica ST2120, was analyzed to assess its virulence and pathogenicity. Methods Multilocus sequence typing (MLST) was employed to assign sequence types (STs) of Bcc strains. Multilocus sequence analysis (MLSA) was conducted for phylogenetic analysis and species identification of novel ST Bcc strains. Whole genome sequencing of ST2120 was performed on the Nanopore platform, followed by genome assembly, gene prediction, functional annotation, and prediction of biosynthetic gene clusters (BGCs) for secondary metabolites. Results Among the 120 Bcc strains, seven species (B. aenigmatica, B. cenocepacia, B. cepacia, B. contaminans, B. vietnamiensis, B. stabilis, and B. multivorans) and 38 STs were identified. Twenty-two novel alleles and 20 new STs were discovered. The novel ST strains were predominantly identified as B. aenigmatica and B. vietnamiensis. B. aenigmatica accounted for 55% of Bcc strains associated with industrial contamination, representing the most prevalent species within the industrial contamination-related Bcc. The genome (8 909 914 bp, G+C content: 65.73%) of B. aenigmatica ST2120 comprised 8 192 protein-coding genes, and the genome data were deposited in NCBI under the accession number CP184468-CP184476. Genomic analysis predicted siderophore-related BGCs for secondary metabolites (e.g., ornibactin C8 and chromobactin), five efflux pump-associated antibiotic resistance genes, and virulence genes linked to secretion systems, host adhesion/invasion, immune modulation, and quorum sensing. Conclusion B. aenigmatica has emerged as a predominant Bcc species in industrial contamination. The genome of B. aenigmatica ST2120 contains comprehensive virulence genes, indicating significant pathogenicity.

Objective The probiotic Escherichia coli Nissle 1917 (ECN) is engineered by synthetic biology to construct a tumor-targeting strain capable of colonizing the tumor tissue, converting glucose and metabolic waste ammonia in the tumor microenvironment into the photosensitizer precursor 5-aminolevulinic acid (5-ALA) and the immunomodulatory amino acid arginine, while synergizing with immune checkpoint inhibitors for enhanced antitumor efficacy. Methods The genes hemA^M, hemL, and argA were co-expressed in ECN, and thyA was knocked out via the λ-Red homologous recombination system to improve the tumor-targeting specificity. Shake-flask fermentation experiments, UV spectrophotometry, and HPLC were employed to quantify 5-ALA and arginine production. The antitumor effects of the engineered ECN were systematically evaluated by in vitro cellular assays and a murine colorectal cancer model. Results The engineered strain achieved 5-ALA and arginine yields of (173.00±11.46) mg/L and (1.70±0.09) g/L, which represented 8.2-fold and 20-fold increases, respectively, over that of wild-type ECN (P<0.000 1). The deletion of thyA enabled selective proliferation of the strain in tumor cells (HCT116 and CT26), with a two-fold increase in OD₆₀₀ compared with that in normal Vero cells (P<0.000 1), confirming enhanced tumor targeting. Both in vitro and in vivo experiments demonstrated sustained synthesis of 5-ALA and arginine in tumors. Compared with wild-type ECN, the engineered strain induced 2.7-fold and 1.9-fold increases in CD8⁺ and CD4⁺ T-cell infiltration (P<0.000 1), alongside 1.7-fold and 2.4-fold elevations in IL-6 and TNF-α secretion (P<0.000 1), respectively. The engineered strain combined with the anti-PD-L1 therapy achieved a tumor volume inhibition rate of 77.6% (P<0.000 1). Conclusion This study establishes a metabolically and immunologically dual-functional ECN platform that synergizes localized delivery of photodynamic therapy precursors, arginine-mediated immunometabolic reprogramming, and immune checkpoint blockade, providing a novel solution for the combined therapy against solid tumors. The engineered system offers a groundbreaking strategy for precise tumor microenvironment modulation, advancing the research on targeted cancer therapeutics.

Objective To screen out a strain with the ability to degrade penicillin G (PENG) and identify the key enzymes involved in PENG catabolism, providing strain and gene resources for the biological treatment of penicillin waste. Methods Bacterial strains capable of utilizing penicillin G potassium (PGK) as the sole carbon source were screened by enrichment culture. Key enzymes involved in the catabolism of PGK were identified by genome and transcriptome analyses, and their evolutionary origins were examined. The key enzymes were expressed and purified, and their kinetics were analyzed. The physiological roles of the key genes in bacterial growth on PGK were revealed by gene knockout and complementation. Results The obtained strain Delftia sp. PG-8 can degrade PGK and utilize it as the sole carbon source for growth. The strain showed the best performance in PENG degradation and growth at pH 7.0, 35 ℃, and 10.00 mmol/L PGK. PgkA catalyzed the rapid degradation of PGK, with K_m=(99.19±19.45) μmol/L and k_cat/K_m=(1.96±0.55)×10⁵ L/(mol·s). Compared with the functionally characterized β-lactamases, PgkA had a unique evolutionary origin. PgkB also had the ability to catalyze the transformation of PGK, while its substrate affinity was only 1/5 that of PgkA, in addition to the lower catalytic efficiency. The degradation and utilization of PGK for growth by strains PG-8-ΔpgkA and PG-8-ΔpgkB were significantly reduced, with PG-8-ΔpgkA showing a more pronounced decline. Although PG-8-ΔpgkAB, in which both pgkA and pgkB were knocked out, still degraded a certain amount of substrate, it was almost unable to use PGK as the sole carbon source for growth. Conclusion PG-8 is the first strain of Delftia capable of using PGK as the sole carbon source for growth. Both pgkA and pgkB play important physiological roles during PG-8 growth on PGK, with pgkA playing a dominant role.

Objective To study the endophytic microbiota in different ecological niches of pepper (Capsicum annuum L.) seedlings at various stages following Ralstonia solanacearum infection, aiming to explore the endophyte migration dynamics triggered by R. solanacearum infection. Methods The copy number of R. solanacearum was quantified by quantitative real-time PCR (qPCR). Samples from roots, stems, and leaves of both infected and healthy pepper plants were collected at 1, 4, and 7 days post-inoculation (dpi). High-throughput amplicon sequencing was employed to analyze the endophytic bacterial and fungal communities. Dual-dimensional analyses integrating microbial copy number and community structures were conducted to elucidate the spatiotemporal dynamics of endophytic microbiota and pathogen proliferation characteristics under R. solanacearum invasion. Results The copy number of R. solanacearum continuously increased in roots and stems post-inoculation, peaking in leaves at 4 dpi and then significantly declining. The infection induced pronounced alterations in endophytic bacterial communities across all tissues, with temporal effects outweighing tissue-specific variations. Roots exhibited heightened sensitivity to pathogen invasion. At 7 dpi, the relative abundance of Bacillota in endophytic bacteria in the plants increased significantly. At the genus level, the relative abundance of Rhizobium, Pseudomonas, and endogenous fungi Fusarium and Aspergillus increased significantly compared with that in the control group. The beta diversity indices and structures of endophytic microbiota in all tissues underwent marked changes during infection. Pseudomonas emerged as a signature bacterial genus in roots, while Aspergillus dominated stems and leaves as a fungal indicator. The co-occurrence network analysis revealed greater complexity of the endophytic microbiota in infected plants, with an elevated proportion of negative correlation edges. Ascomycota served as pivotal network hubs, reflecting enhanced antagonistic interactions and inter-microbial associations under pathogen stress. Ten potential antagonistic microbial taxa were identified, including six bacterial taxa of Clostridia (Bacillota). Conclusion This study delineates the proliferation pattern of R. solanacearum in pepper seedlings and characterizes the structural and migration dynamics of endophytic microbiota following pathogen invasion.

The nucleotide-binding domain leucine-rich repeat and pyrin domain-containing receptor 3 (NLRP3) inflammasome, a crucial element of innate immunity, plays a pivotal role in immune responses and disease pathogenesis. Dysregulated activation of the NLRP3 inflammasome is strongly linked to the onset of various diseases. Recent studies have demonstrated that the Lactobacillaceae can exert anti-inflammatory effects by regulating the NLRP3 inflammasome activity. Therefore, this review outlines the anti-inflammatory mechanisms by which the Lactobacillaceae regulate the NLRP3 inflammasome activity both directly and indirectly. Additionally, we discuss the roles of specific strains, such as Lactiplantibacillus plantarum, Lacticaseibacillus casei, and Lacticaseibacillus rhamnosus, in intestinal inflammatory diseases, hepatic disorders, neurodegenerative diseases, and metabolic/immune-related conditions. This review aims to lay a foundation for an in-depth investigation of the precise mechanisms underlying the Lactobacillaceae-mediated regulation of the NLRP3 inflammasome and provides novel therapeutic strategies for inflammatory diseases.

There are a large number of non-rhizobia endophytes in addition to rhizobia in leguminous root nodules, which are of great significance for promoting plant growth and improving the bacterial abundance in root nodules. Some NREs can not only help rhizobia expand their host range but also participate in the leguminous plant-rhizobia symbiotic nodulation process. In this review, we systematically summarize the genetic diversity, classification, and functions of NREs, specifically describe the pathways of NREs entering rhizobia, the interaction mechanism between NREs and rhizobia, and the diversity of NREs in soil ecosystems, and discuss the application potential and future research directions of NREs. Furthermore, this article summarizes the current research progress in leguminous plant-rhizobia-NREs interactions and explores the methods of improving crop productivity and health through interactions mediated by nodule microecology, aiming to provide theoretical support for sustainable agricultural development.