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.

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 Bacteria of Pseudomonas are the main cause of food-borne and clinical infections. At present, mass spectrometry and 16S rRNA gene are widely used to identify Pseudomonas, while the facilities relied on are expensive and require cumbersome operation. Internationally, the numerical identification products require manual single-sample loading procedures, which are cumbersome. This study aims to develop a numerical identification kit for Pseudomonas with high accuracy and simple operation. Methods On the basis of the existing biochemical reaction data of Pseudomonas, we developed a numerical identification model via the branching diagram method and designed and optimized 11 biochemical matrix formulas for microquantization. We then used the kit to identify the standard strains and isolates of Pseudomonas and compared the results with those from mass spectrometry and PCR to evaluate the performance of the kit. Results A numerical identification kit was developed, and it was capable of identifying 10 species of Pseudomonas with just one sample addition. The accuracy rate of the kit in the identification for 5 standard strains and 135 isolates reached 97.04%, and the accuracy rate in actual samples was 97.74%. The biochemical test was stable and reproducible, and the identification cost (25 CNY/sample) of the kit was only 10% of that (240 CNY/sample) of the comparable product from bioMérieux (France). Conclusion The numerical identification kit developed in this study for Pseudomonas has simple operation, a low price, and high accuracy, which can be used in clinical diagnosis and food detection.

Streptococcus pneumoniae is a common opportunistic pathogen that can cause various infectious diseases, including acute otitis media, bronchitis, sinusitis, community-acquired pneumonia, septicemia, and purulent meningitis. Autophagy, a lysosome-dependent intracellular degradation pathway, plays a dual regulatory role in both bacterial infection and host defense against pathogens. During S. pneumoniae infection, host cells can activate xenophagy to eliminate invading bacteria. However, this pathogen has evolved multiple evasion strategies, such as interfering with autophagosome maturation, escaping autophagic encapsulation, and even hijacking the autophagy pathway to promote intracellular survival and dissemination. Recent years have witnessed significant progress in understanding the molecular mechanisms underlying the dynamic interplay between S. pneumoniae and host autophagy systems during bacterial infection, yet a systematic review synthesizing these findings remains unavailable. This review focuses on the interaction network and key mechanisms of S. pneumoniae with host cell autophagy, aiming to provide theoretical foundations and research perspectives for developing novel targeted therapeutic strategies against S. pneumoniae infections.

Mobile genetic elements drive bacterial evolution, while exposing bacteria to the risk of invasion by “selfish genes”. In the arms race with mobile genetic elements, bacteria have evolved a range of immune systems that can protect hosts from invading nucleic acids. These immune systems are capable of preventing the invasion of mobile genetic elements, degrading invading nucleic acids, inhibiting the replication or transcription of invading nucleic acids, or inducing abortive infections to protect the population. Although much is known about the working mechanisms of these host immune systems, it remains unclear how bacteria orchestrate different defense strategies in response to different stages of nucleic acid invasion. Based on our research and different immune strategies of bacteria to limit mobile genetic elements in different spatiotemporal dimensions, this review summarizes and classifies the host immune systems. The elucidation of these multilayered immune mechanisms not only reveals the arms race between host and mobile gene elements in the evolutionary process but also underpins the development of new biotechnologies.

Bacterial glycoproteins, glycolipids, and polysaccharides are collectively known as glycans, which can serve as pivotal pathogenic factors leading to infection. Bacterial protein glycosylation mainly includes N-glycosylation, O-glycosylation, S-glycosylation, and arginine glycosylation. Glycolipids and polysaccharides are also important glycoconjugates, mainly including lipopolysaccharides, lipoarabinomannan, rhamnolipids, peptidoglycan, teichoic acids, and capsular polysaccharides. Bacterial glycoconjugates can promote host-pathogen interactions, influencing bacterial virulence, drug resistance, and biofilm formation, thereby facilitating bacterial infection. In addition, bacterial glycoconjugates can exert dual effects by modulating the host immune system: on one hand, aiding bacteria in achieving immune evasion and causing host infection; on the other, activating host immunity to help eliminate bacteria and suppress infection. This article provides an overview of bacterial glycans regarding the types, structural characteristics, roles in bacterial adhesion and colonization, and regulation of host immune responses and summarizes the effects of bacterial glycans on infection, aiming to offer a distinct perspective from glycoimmunology and an alternative strategy for clinical prevention and treatment of bacterial infectious diseases.

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.

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.

In multicellular organisms, cell death is perpetually in a dynamic process. Apoptosis as a pivotal form of regulated cell death, mainly encompasses two pathways: the intrinsic pathway and the extrinsic pathway. During the pathogen infection, host cells are capable of eliminating the infected cells through apoptosis. On the other hand, pathogens have evolved a multitude of strategies to regulate host cell apoptosis. These strategies involve the use of effector proteins to modulate cellular signaling pathways, the regulation of the expression of apoptosis-related genes, the control of key proteins within the apoptosis pathway, and the modulation of the activity of proteases in the Caspase family. This article provides a comprehensive review of the molecular mechanisms and strategies by which intracellular pathogens, such as viruses, bacteria, parasitic fungi, and parasites, regulate host cell apoptosis. The aim is to offer valuable references for further exploration of the intricate interaction mechanisms between pathogens and hosts.