Objective To isolate lactic acid bacteria (LAB) with the ability to degrade milk fat, providing a theoretical foundation and technical support for dairy fermentation process optimization and probiotic development. Methods Primary screening employed media with butter as the main carbon source, followed by secondary screening using media with butter as the sole carbon source. The target strains were validated via carbon-free media. The selected strains underwent chromogenic assays for lipase characterization. Fermentation properties were assessed through viable count, acidity, acid value, and free fatty acid measurements. Probiotic potential was evaluated via acid/bile salt tolerance and cholesterol reduction assays. Results Through primary screening, secondary screening, and validation, ten strains with the ability to degrade milk fat were selected. Among them, a strain with faster growth than the others was identified as Lactobacillus delbrueckii grx601 through morphological and molecular biological characterization. This strain exhibited high lipase activity during logarithmic and stationary phases, with intracellular and extracellular enzyme activities of 14.14 U/mL and 11.45 U/mL, respectively. Enzymatic characterization showed that the optimal substrate for intracellular and extracellular lipases was p-nitrophenol palmitate, with the optimal reaction conditions of pH 7.0 and 40 ℃. The relative activity remained above 50% at 5% NaCl, which indicated certain salt tolerance. The fermentation characteristic experiment showed that L. delbrueckii grx601 significantly increased the acidity, acidity value, and free fatty acid content during the fermentation process. Moreover, the survival rates of L. delbrueckii grx601 in artificial simulated solutions with pH 3.0 and 0.30% bile salt were 83.87% and 47.70%, respectively, which indicated acid/bile salt tolerance of the strain. In addition, the cholesterol degradation rate of the strain was 7.95%. Conclusion L. delbrueckii grx601 was successfully isolated and characterized as a potent milk fat-degrading strain. Its high intra/extracellular lipase activity, favorable enzymatic properties, robust fermentation performance, and probiotic attributes (acid/bile salt tolerance, cholesterol reduction) indicate significant potential for dairy fermentation and probiotic applications.

In recent years, the widespread application of new technologies such as viral metagenomics has expanded our understanding of viral diseases in giant pandas. In addition to the previously reported infections with canine distemper virus, rotavirus, and parvovirus, the viruses carried by giant pandas exhibit increasing diversity and unique genetic variation characteristics. The growing population size and density of giant pandas post serious challenges to the population biosecurity, especially the prevention and control of viral diseases. To better understand the epidemiological characteristics of viral diseases in giant pandas, as well as the current status of the prevention and control for the development of effective strategies, we review the studies about viral diseases in giant pandas. This paper systematically elucidates the infection characteristics and hazards of major viral pathogens, as well as diagnostic methods, treatment measures, and preventive strategies. Additionally, the paper explores the bottlenecks and challenges encountered in developing and applying vaccines for giant pandas and the difficulties faced in viral disease research and proposes future research directions and recommendations, aiming to provide a scientific basis for preventing and controlling viral diseases in giant pandas.

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.

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 screen the biocontrol bacterial isolates with antagonistic activity against root rot pathogens of Panax notoginseng from the rhizosphere of Bletilla striata in a P. notoginseng-B. striata rotation system, identify the isolates, and evaluate their control effects, thereby providing a scientific basis for the application of P. notoginseng-B. striata rotation in alleviating continuous cropping obstacles and screening biocontrol strains from the rhizosphere of the plants for rotation rather than from that of target plants in the plant rotation system for controlling soil-borne diseases in the field. Methods The dilution plate method was employed to isolate culturable microorganisms from the rhizosphere soil of B. striata. The antagonistic activities of the isolates against root rot pathogens of P. notoginseng were evaluated via the dual culture assay. Molecular identification was performed based on the 16S rRNA gene sequence. In pot experiments, antagonistic bacteria were inoculated, and then the ability of antagonistic bacteria to control root rot was evaluated based on the root rot incidence of P. notoginseng. Results The rotation with B. striata significantly reduced the incidence and disease index of P. notoginseng root rot compared with continuous cropping. A total of 200 bacterial strains were isolated from the rhizosphere soil of B. striata, from which 25 strains exhibiting antagonistic activities against the root rot pathogens including Ilyonectria destructans RS6, Fusarium solani F3, and Fusarium oxysporum Z5 of P. notoginseng were screened out. The isolation efficiency of antagonistic bacteria was 12.5%. The 25 strains were identified as 12 species belonging to 5 genera, demonstrating rich diversity. There were 14 strains of Bacillus sp., including 4 strains of B. subtilis, 2 strains of B. velezensis, 6 strains of B. amyloliquefaciens, 1 strain of B. cereus, and 1 strain of B. toyonensis. There were 5 strains of Acinetobacter, including 2 strains of A. johnsonii, 2 strains of A. junii, and 1 strain of A. pittii. There were 4 strains of Pseudomonas, including 3 strains of P. putida and 1 strain of P. fulva. In addition, 1 strain of Enterobacter asburiae and 1 strain of Aeromonas caviae with antagonistic activities were isolated. Four strains (B. amyloliquefaciens BJ1, B. subtilis BJ7, B. amyloliquefaciens BJ8, and A. johnsonii YB10) antagonistic to all the three pathogens were applied to continuous cropping soil. They significantly reduced the root rot incidence and enhanced the fresh weight of P. notoginseng. Conclusion The rhizosphere soil of B. striata in rotation with P. notoginseng harbors diverse biocontrol strains against the root rot pathogens of P. notoginseng. This study lays a theoretical foundation for the rotation of P. notoginseng with B. striata to alleviate continuous cropping obstacles.

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 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 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 elucidate and compare the diversity, structure, and functional characteristics of gut microbiota in sympatric fish species from a perspective of microbial ecology and explore the role of gut microbiota in feeding habit and ecological niche differentiation. Methods Foregut, midgut, and hindgut samples from Gymnocypris eckloni and Schizopygopsis pylzovi, along with their aquatic environmental samples, were collected from the upper Yellow River. The gut microbiota and potential functions were compared by 16S rRNA gene high-throughput sequencing and multiple bioinformatics approaches. Results Microbial alpha diversity followed the trend of aquatic environment>S. pylzovi>G. eckloni (P<0.05). In G. eckloni, alpha diversity was highest in the foregut, whereas in S. pylzovi, it decreased progressively from the foregut to the midgut and then to the hindgut. Beta diversity analysis based on clustering and CPCoA demonstrated that microbial communities derived from different gut segments of the same species were more similar to each other than those derived from the same gut segment of different species, indicating that the differences attributable to species were greater than those attributable to gut segments (P<0.001). Pseudomonadota accounted for over 50.00% of the gut microbiota in all sample types, while Bacillota comprised more than 25.00% in the guts of both fish species, which was significantly higher than that (3.80%) observed in the aquatic environment. Fusobacteriota and Cetobacterium were nearly absent in water and S. pylzovi but showed high abundance in the midgut and hindgut of G. eckloni. Enterococcus was specifically enriched in the hindgut of G. eckloni, while Lactococcus were predominantly found in the hindgut of S. pylzovi. PICRUS2 functional prediction revealed that gut microbiota of both species primarily enriched amino acid and carbohydrate metabolism pathways. The enriched metabolic pathways varied significantly across different gut segments of S. pylzovi, while significant differences in signaling molecules and interaction, cardiovascular diseases, and metabolism of terpenoids and polyketides were noted for the same gut segments between the two species. Conclusion There were significant differences in the microbiota composition and diversity in the gut between the two fish species and their aquatic environments, with distinct gut microbiota functions for each species. This study establishes a micrological foundation for research on the feeding habit and ecological niche differentiation of fish and provides theoretical support for exploitation of gut microbial resources and conservation and resource management of plateau fish species.