The spread of antibiotic resistance has made bacterial infections a global public health crisis, posing serious challenges to conventional antibiotic therapy and creating an urgent need to develop novel antibacterial strategies. As viruses are capable of specifically lysing bacteria, phages represent a promising alternative therapeutic strategy due to their unique killing mechanisms and high host specificity. Nevertheless, they face limitations in monotherapy due to their narrow host ranges and the emergence of phage-resistant bacteria. In recent years, phage-antibiotic combination therapy has garnered significant attention. It demonstrates unique advantages in enhancing bactericidal effects, synergistically inhibiting dual-resistance mechanisms, broadening the host range, disrupting biofilms, and treating complex infections. This therapy not only overcomes the limitations of single phage therapy but also paves new avenues for treating multidrug-resistant bacterial infections. This review systematically summarizes the synergistic mechanisms, key influencing factors, current challenges, and optimization strategies of phage-antibiotic combination therapy, aiming to provide a theoretical foundation and practical guidance for further research and clinical translation in this field.

Objective The outbreaks of infectious bovine rhinotracheitis (IBR) have been reported in multiple regions across China. To systematically characterize the molecular features and biological properties of the predominant strains of infectious bovine rhinotracheitis virus (IBRV) and provide etiological insights for evidence-based prevention and control against IBR. Methods We collected the bovine lung tissue for detection of common bovine respiratory viruses by PCR. Viral isolation was performed with MDBK cells, and then metagenomic sequencing was conducted to determine and analyze complete genome sequences of the viruses. Viruses were purified via the plaque assay and subcultured to the 9th generation (F9) for determination of the 50% tissue culture infectious dose (TCID₅₀), monitoring of one-step growth kinetics, and observation of viral particle morphology via electron microscopy. Two IBRV-seronegative healthy adults of cattle were intranasally inoculated with the F9 suspension (2.5 mL/nostril), while one additional head of cattle was housed in close contact. The clinical manifestations were monitored, including body temperature fluctuations and viral shedding dynamics. Results PCR detection revealed the presence of both IBRV and bovine coronavirus (BCoV) in the bovine lung tissue. After inoculation into MDBK cells, obvious cytopathic effects were observed at the third passage. Metagenomic sequencing confirmed the virus as IBRV, with a whole genome length of 134 678 bp. This isolate was designated as IBRV GSLT/04/2024. The TCID₅₀ of F9 was 10^5.5 TCID₅₀/mL, and no mutation was detected in the gB, gC, gD, or gE gene. Based on the gC gene and whole genome sequences, this strain was classified into the IBRV 1.2b subtype lineage. Viral shedding began on day 5 post-inoculation in the inoculated cattle and on day 10 in the contact cattle, lasting for approximately 10 days. The amount of viral shedding followed the order of nasal swabs>oral swabs>rectal swabs>ocular swabs. On day 30 post-inoculation, IBRV genes were only detected in the colon tissue. IBR-specific antibodies were detected on approximately day 7 in the inoculated cattle and on day 10 in the contact cattle. Conclusion We successfully isolated a novel IBRV subtype 1.2b strain with high infectivity in adult cattle. The findings provide epidemiological and etiological evidence to trace the recent surge in IBRV prevalence across China.

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.

With the development of human industrial activities, nitrogen (N) emissions and atmospheric N deposition have increased significantly. When atmospheric N deposition exceeds the critical load that plants can bear, it may exert a negative effect on plants and lead to a decrease in species abundance. As an important biotic factor affecting species abundance, mycorrhizae can affect plant diversity and community structure through nutrient supply and hyphal network mechanism. Objective To compare the critical load of N deposition of understory herbaceous plants with different mycorrhizal types and explore how mycorrhizal types affect the responses of understory herbaceous plants to N deposition. Methods According to the database of long-term N deposition critical load of forest herbaceous plants, and the published literature, critical load database of herbaceous plants under different mycorrhizal types of forest forests in response to N deposition was established. We identified three mycorrhizal types of forest dominant species, which included arbuscular mycorrhiza (AM), ectomycorrhiza (ECM), and AM+ECM. The effects of mycorrhizal types on the critical load of N deposition of understory herbaceous plants were investigated. Results The critical load of N deposition of understory herbaceous plants varied in forests of different mycorrhizal types (P<0.05). The critical load of N deposition was the highest [9.28 kg N/(ha·a)] in the forest of the AM+ECM type, the second [8.41 kg N/(ha·a)] in the forest of the ECM type, and the lowest [7.19 kg N/(ha·a)] in the forest of the AM type. In forests of different mycorrhizal types, the critical loads of understory herbaceous plants of different functional groups (gramineous and non-gramineous) in response to N precipitation were consistent with the responses of all understory herbaceous plants of different mycorrhizal types. N deposition caused changes in the abundance of understory herbaceous plants. The species abundance of understory herbaceous plants in the forest of the AM type showed an increasing trend, while that in the forest of the ECM type mainly decreased. Conclusion Mycorrhizal types affect the critical load of N deposition of understory herbaceous plants (P<0.05), which is related to the niche differentiation, N concentration of litter, and N acquisition strategies of different mycorrhizal types of plants. In addition, the abundance of understory herbaceous plants will also vary due to different mycorrhizal types.

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 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.

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.

Objective To breed Bifidobacterium adolescentis strains that can adapt to the gastrointestinal environment of felines and have strong intestinal colonization capabilities. Methods B. adolescentis was isolated from the feces of felines with long and regular life spans. The original strain QC-Y (with the life span extension rate reaching 33.85%) was selected through biomass assessments and mouse life span experiments and it was identified as B. adolescentis. After radiation-induced mutation, QC-Y-09 was screened out by the biomass assessment, gastrointestinal tolerance domestication, and evaluation. Results QC-Y-09 showed the biomass 55.667 times and the tolerance score 5.66 times that of QC-Y. Moreover, the tolerance of the strain to the feline gastrointestinal environment showed good genetic stability. The survival rates of the 10th generation of QC-Y-09 in the artificial gastric juice, intestinal juice, anaerobic, and micro-aerobic environments were 18.80%, 41.60%, 93.26%, and 48.39%, respectively, which were 62.67%, 108.53%, 97.92%, and 94.40% of those of the original generation. The intestinal colonization test showed that the colonization ability of QC-Y-09 in felines was significantly stronger than that of QC-Y and human-derived B. adolescentis. Seven days after the feeding of the microbial inoculum was stopped, the viable count of B. adolescentis in the feline feces of the QC-Y-09 group still reached 4.37 lg CFU/g, which was 1.74 lg CFU/g and 3.02 lg CFU/g, respectively, higher than those of the QC-Y group and the human-derived B. adolescentis group. In addition, QC-Y-09 had a good relieving effect on the feline food change stress, reducing the feline food change stress rate by 85.71%. The results of SNP analysis showed that QC-Y-09 was significantly different from QC-Y at the gene level, and the differentially expressed genes were mainly enriched in the ribosome structure and aminoacyl-tRNA biosynthesis pathway. Conclusion Feline-derived B. adolescentis QC-Y-09 bred in this study can effectively adapt to the gastrointestinal environment and colonize the intestines of felines. This study provides both theoretical and practical bases for the application of B. adolescentis in functional food for felines.

Objective As a zoonotic pathogen, Proteus mirabilis poses a serious challenge to public health due to its multi-antibiotic resistance and the synergistic effect of virulence genes. To characterize the antibiotic resistance transmission of bacteria in the food chain in Zhejiang Province, this study systematically monitored the antibiotic resistance phenotypes and genes of isolates from cattle slaughterhouses and farmers’ markets, and analyzed the distribution differences of antibiotic resistance genes (ARGs), virulence genes (VGs), and mobile genetic elements (MGEs). Methods A total of 384 samples (feces, carcasses, environment, etc.) were collected from cattle slaughterhouses and farmers’ markets, and the strains were identified by 16S rRNA gene sequencing. Twenty ARGs and 10 VGs were detected by the K-B disc diffusion method and PCR, and the ARGs and VGs carried by P. mirabilis were analyzed. The ARG clusters were analyzed by sequencing of integron gene cassettes, and the co-occurrence network of ARGs, VGs, and MGEs was constructed. Subsequently, conjugative transfer experiments were carried out to explore the horizontal transmission potential of ARGs. Results A total of 101 strains of P. mirabilis were isolated, with the total isolation rate of 26.30%. The isolation rate of strains from slaughterhouses (33.85%) was significantly higher than that from farmers’ markets (18.75%). The resistance rates to ceftriaxone sodium, amoxicillin, and erythromycin were all over 90.00%. Among the ARGs, bla_TEM (89.09%), sul1 (77.71%), and tetA (63.29%) had the highest detection rates, and the distribution of ARGs in slaughterhouses was more complex. The VGs fliL (92.08%) and zapA (80.20%) were highly expressed in the isolates, which suggested potential pathogenicity. The detection rate of integrons in slaughterhouses was significantly higher than that in farmers’ markets, and PCR amplification results showed that there were a variety of ARGs, including aminoglycoside and trimethoprim resistance genes. Co-occurrence network analysis showed that ARGs, VGs, and MGEs had significantly positive correlations, and type I integron (intI1) was the hub gene. Conjugative transfer experiments confirmed that bla_TEM could be transmitted across species via horizontal transmission. Conclusion Compared with farmers’ markets, slaughterhouses are key nodes in the spread of antibiotic resistance due to the antibiotic exposure pressure, high organism density, and rich mobile components. The findings emphasize the importance of strengthening antibiotic management and monitoring the transmission chain of ARGs, providing a scientific basis for the prevention and control of antibiotic resistance under the framework of “One Health”.

Objective The mesophilic salt-tolerant xylanase XynRBM26, a member of the GH10 family, holds significant application value in industrial fields such as animal feed. This study improved the thermostability of this enzyme by protein modification via rational design, aiming to lay a foundation for the industrial application of XynRBM26 preparations. Methods The bioinformatics software FoldX was used to conduct positionscan of the 3D structure predicted by AlphaFold 2.0 for XynRBM26. The mutants with free energy changes less than -0.5 kcal/mol were selected to construct an initial electronic library. According to the Pro effect and screening principles for potential mutants, an electronic library composed of Pro mutations was subsequently established. Finally, site-directed mutagenesis was employed to construct mutant genes, and positive mutants were screened after heterologous expression, purification, and experimental verification. Results After screening of the initial potential mutants, a small and precise mutant library consisting of 21 Pro effect mutants was constructed. All the mutants were experimentally validated, and positive single-point mutants D222P, V182P, D344P, and A352P with significantly increased T_m values were screened out. Through subsequent stacking screening, a three-point stacked Pro effect mutant with superior properties was obtained. The combination of this mutant with the experimentally screened positive mutant G115D produced the most stable mutant M4 (G115D-D222P-D344P-A352P). Compared with wild-type XynRBM26, M4 showed increases of 6.5 °C and 5 °C in T_m and optimal temperature, respectively. Moreover, M4 presented the half-life (t_1/2) at 55 °C 7.5-fold longer than the wild type, and its relative activity at the optimal temperature was 3.44 folds that of the wild type. Conclusion Screening thermostable mutants of the salt-tolerant xylanase XynRBM26 of the GH10 family based on the Pro effect and two different effect superimposing strategies is an effective approach.