Objective To systematically understand the antibiotic resistance and the distribution of resistance genes of intestinal antibiotic-resistant bacteria in Corvidae species on plateaus. Methods The conventional culture method and sequencing were employed to analyze 71 intestinal samples from five typical Corvidae species in plateau cities. Results A total of 70 bacterial strains were isolated, belonging to 25 species, 14 genera of 3 phyla. The highest number of strains was isolated from the medium containing sulfamethoxazole and the intestinal samples of Corvus macrorhynchos, with Enterococcus and Enterococcus mundtii being the dominant genus and species, respectively. The Kirby-Bauer disk diffusion test revealed that the isolated strains had the highest resistance rate to polymyxin antibiotics, and all the strains exhibited multidrug resistance, with nearly 40% being superbugs resistant to 10 or more antibiotics. Among the seven major categories of resistance genes, carbapenem resistance genes showed the highest detection rate, with tetD being the most frequently detected resistance gene. The detection rates of integrons and gene cassettes were both low. Conclusion Avian species of Corvidae exhibit high diversity and widespread prevalence of multidrug-resistant bacterial strains in their intestinal microbiota. Antibiotic resistance genes are widely present within these strains and exhibit significant transmission potential. As a result, they serve as veritable reservoirs and vectors for antibiotic-resistant bacteria and resistance genes, posing challenges and threats to human public health, medical care, and environmental safety. This study fills the gap in research on intestinal antibiotic-resistant bacteria and their antibiotic resistance in Corvidae birds, providing a scientific basis for subsequent assessments of the transmission risk of antibiotic resistance mediated by wild birds and the formulation of prevention and control strategies.

The β-barrel assembly machinery (BAM) complex is an essential apparatus that is responsible for the assembly of β-barrel outer membrane proteins (OMPs) into the outer membrane of Gram-negative bacteria. Its functional defects can lead to bacterial death, and thus it is established as a new target for antibacterial drug development. The subunit composition of the BAM complex varies across different bacterial species and in Escherichia coli, it is composed of a core subunit BamA and auxiliary lipoproteins BamB-E. BamA, as a member of the Omp85 family, mediates the folding and release of substrate OMPs through the dynamic conformational changes of its β-barrel structure that are regulated by lipoproteins. In the present review, we summarized recent progress in distinguishing the minimal functional unit, complete functional unit, and other functional units of the BAM complex in E. coli. Moreover, by reviewing the drug screening studies targeting the BAM complex, we provided an overview of new strategies to combat the drug resistance of Gram-negative bacteria.

Objective To investigate the effects of changes in single factors such as pH, metal ions, and NaCl concentration in the MG medium on the growth of Virgibacillus salexigens DSM 11483 and the yield of 5-hydroxyectoine (5-HE), optimize the culture conditions, and explore the mixed culture conditions of Halomonas campaniensis XH26 with V. salexigens DSM 11483 and the change in the yield of 5-HE. Methods We used a spectrophotometer was used to monitor the biomass (OD₆₀₀) of bacteria. The HPLC method was used to measure the yields of ectoine and 5-HE. The one-sample t-test was conducted to analyze the difference significance of the experimental data. Results The optimal culture conditions for V. salexigens DSM 11483 were as follows: pH 9.0, FeSO₄·7H₂O concentration of 1.00 mmol/L, and NaCl concentration of 2.0 mol/L. In this medium, the yields of ectoine and 5-HE were 200.4 mg/L and 80.0 mg/L, respectively. After “feeding” V. salexigens DSM 11483 with 40.0 mmol/L ectoine and culturing for 72 h, the yield of 5-HE reached 1 373.5 mg/L, which was 17.2 times that in the control group. After 72 h of mixed culture of H. campaniensis XH26 cultured for 24 h with V. salexigens DSM 11483 cultured for 36 h, the yields of ectoine and 5-HE were 1 535.1 mg/L and 168.7 mg/L, respectively, which were 7.7 times and 2.1 times the yield of V. salexigens DSM 11483 in pure culture. Conclusions The mixed culture of halophilic bacteria can make full use of their respective advantages to improve the synthesis and transformation efficiency of ectoine, demonstrating further research value.

Objective To isolate multifunctional phosphate-solubilizing bacteria (PSB) exhibiting psychrophilic adaptation and saline-alkaline tolerance in response to the ecological challenge of phosphorus limitation in saline-alkaline soils in cold regions, evaluate their phosphate-solubilizing efficiency and environmental adaptability, and preliminarily investigate their phosphate-solubilizing mechanisms. Methods We used an inorganic phosphorus-selective medium to isolate bacterial strains from saline-alkaline soils in Baicheng, Jilin Province. The phosphate-solubilizing capacity was quantitatively determined through the molybdenum-antimony colorimetric method. Taxonomic identification was performed through morphological characterization and phylogenetic analysis based on 16S rRNA gene sequences. The phosphate solubilization conditions were optimized via multi-parameter gradient optimization. HPLC was employed to quantify organic acid metabolites. Phenol-sulfuric acid assay and crystal violet staining were employed to characterize biofilm formation and extracellular polysaccharide (EPS) synthesis. Results The isolated strain Pseudomonas psychrophila MPP2402 demonstrated broad-spectrum environmental adaptability, maintaining stable growth at 5-30 ℃, pH 7.0-10.0, and 0.2-0.8 mol/L NaCl. The strain achieved 574.66 mg/L soluble phosphorus (14.8% increase) under optimal conditions: 15 ℃, pH 7.0, 0.4 mol/L NaCl, 1% inoculum density, and 5 g/L Ca₃(PO₄)₂. MPP2402 may exert the phosphate-solubilizing effect through the secretion of organic acids such as succinic acid (51.53 μg/mL), oxalic acid (22.84 μg/mL), tartaric acid (15.11 μg/mL), and malic acid (5.93 μg/mL), which worked in concert to solubilize phosphate. Additionally, the strain utilized EPS to construct a biofilm barrier and regulated the viable count in adverse environments such as low-temperature and saline-alkaline conditions. Conclusion The successful isolation of MPP2402 establishes a foundational resource for developing efficient saline-alkaline tolerant microbial agents and improving soil nutrient management in cold-region ecosystems.

Objective To investigate the effect of yeast dietary fiber (YDF) on arsenic-induced apoptosis in Saccharomyces cerevisiae and decipher the possible mechanism. Methods The relative survival rate, apoptosis, and antioxidant indicators were determined by the spread plate method, spectrophotometry, fluorescence microscopy, and RT-qPCR. Results The exposure to arsenic significantly decreased the relative survival rate, elevated the intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and induced apoptosis. However, in the presence of YDF (0.5 mg/mL or 1.0 mg/mL) and arsenic, the arsenic-induced toxic effects were effectively attenuated, which was evidenced by increases in the relative survival rate, content of glutathione, activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX), and relative expression of antioxidant enzyme genes (SOD1, CTA1, CTT1, and GPX2). Moreover, the treatment with both YDF and arsenic lowered the ROS and the MDA levels, significantly down-regulated the relative expression levels of pro-apoptotic genes (AIF1, NMAⅢ, and NUC1), and significantly reduced apoptotic cells compared with the treatment with arsenic alone. Conclusion YDF regulates the antioxidant system to attenuate the arsenic-induced cytotoxicity, thereby alleviating the arsenic-induced apoptosis.

Objective To investigate the effects of the antidepressant mirtazapine on the microbial resistome in complex intestinal environments. Methods We employed read mapping and metagenomic assembly to analyze the antibiotic resistance genes (ARGs) and their bacterial hosts based on metagenomic sequencing data of fecal and cecal content samples. Results A total of 29 classes of ARGs, comprising 610 subtypes, were identified. Bacitracin-, tetracycline-, and vancomycin-class ARGs were the predominant types. Chronic restrain stress (CRS) increased the total abundance of ARGs, significantly elevating the abundance of high-risk ARGs belonging to aminoglycoside, MLS (macrolide-lincosamide-streptogramin), and tetracycline classes (e.g., tetM, tetO, and tet40). Oral administration of mirtazapine exhibited initial microbiota-dependent effects on the resistome. It increased the total abundance of ARGs in healthy rats but decreased that in depressed rats. In addition, mirtazapine significantly enhanced the abundance of vancomycin-, aminoglycoside-, and mupirocin-class ARGs in healthy rats, as well as the tetracycline resistance gene tetP and multidrug resistance gene ompR in depressed rats. Bacillota, Bacteroidota, and Pseudomonadota were the dominant phyla of gut microbiota and served as the primary bacterial hosts of ARGs. Bacillota, as the main host phylum for aminoglycoside and MLS-class ARGs, showed increased abundance after CRS treatment, which was a key factor driving the significant enrichment of these two ARG classes. Furthermore, CRS increased the proportion of pathogenic bacteria such as vancomycin-resistant enterococci. Lactobacillus and Blautia were identified as potential hosts of tetP and ompR, respectively. The significant increases in the abundance of Lactobacillus and Blautia in the intestines of depressed rats after oral mirtazapine administration were critical factors for the marked enrichment of tetP and ompR. Conclusion CRS increases gut microbiota resistance risks by elevating the abundance of high-risk ARGs and pathogenic bacteria carrying ARGs. The effects of oral mirtazapine on the gut resistome are dependent on the initial microbiota composition. This study provides insights into the relationship between non-antibiotic drugs and gut microbiota resistance, offering important implications for the prevention and control of antibiotic resistance transmission.

Objective To investigate the mechanism by which the endophytic fungus Trichoderma harzianum Rifai help the seedlings of the rare medicinal plant Camphora migao (H. W. Li) Y. Yang, Bing Liu & Zhi Yang to defend against drought stress. Methods We simulated different drought stress gradients using the potted weighing method after inoculation of C. migao seedlings with T. harzianumvia rhizosphere injection and investigated the plant growth, physiological, and biochemical indexes. Results Under different drought conditions, inoculation with T. harzianum significantly increased the growth indexes such as biomass, plant height, and root growth of C. migao seedlings, compared with the uninoculated control group. Furthermore, T. harzianum significantly increased the activities of antioxidant enzymes and the content of osmotically regulation substances, reduced the malondialdehyde content, and elevated the content of photosynthetic pigments in the seedling leaves, which effectively mitigated the drought stress effects on the growth and development of C. migao seedlings. Conclusion T. harzianum improved the physiological responses of C. migao seedlings to drought stress by regulating osmotic balance and maintaining the stability of antioxidant system.

Viruses are known as the most abundant and diverse biological entities on Earth and regarded as key ecological drivers in ecosystems. The discovery of giant viruses has challenged the conventional understanding of virology and the definition of life with their microscale-virions, megabase-genome sizes, and remarkably numerous eukaryote-specific genes, which were once considered to be hallmark genes of cellular life but barely seen in viruses. Therefore, these biological characteristics of giant viruses blur the boundary between viruses and cellular life. Metagenomics studies have revealed that giant viruses are globally distributed in marine, freshwater, and soil ecosystems, and their geographical distribution is influenced by environmental factors such as temperature, latitude, and host range. Giant virus genomes include core metabolic genes, which enhance environmental adaptability by regulating host metabolism. In addition, giant viruses may even be involved in the horizontal transfer of antibiotic resistance genes. We review the research progress in giant viruses in terms of their diversity, biogeographic distribution, ecological relationships with hosts and intracellular parasites, reprogramming of host cell metabolic systems, driving forces in biogeochemical cycles, and potential impacts on human health to explore the ecological roles of giant viruses from multiple dimensions. This review aims to revolutionize our knowledge of viruses by revealing the ecological significance of giant viruses and their roles in global biogeochemical cycles.

Porcine hemagglutinating encephalomyelitis virus (PHEV), a member of the betacoronavirus genus, is widespread in swine herds and the only known coronavirus causing neurological diseases in pigs. Objective To characterize the genomic features and phylogenetic relationship of a PHEV strain isolated from China. By investigating the biological properties of the virus, we assessed its epidemiological status and identified genetic variation patterns and evolutionary trends, providing a scientific basis for developing targeted prevention and control strategies. Methods RT-PCR detection was performed on suspected PHEV-positive samples collected from a large pig farm in Jiangsu Province, China, followed by virus isolation. The isolated virus was validated by indirect immunofluorescence assay (IFA), transmission electron microscopy (TEM), and whole genome sequencing. Phylogenetic analysis was performed based on the complete genome, S gene, HE gene, and NS2 gene. Results A PHEV strain, designated as PHEV JS-2025, was successfully isolated from the brain tissue sample. IFA showed strong red fluorescence signals in the cytoplasm, and TEM revealed typical coronavirus particles with a diameter of approximate 150 nm. The strain showed vigorous propagation in HRT-18 cells, reaching the peak viral titer at 72 h, with a 50% tissue culture infectious dose (TCID₅₀) of about 10^4.3 TCID₅₀/mL. PHEV JS-2025 could infect HRT-18, NPTR, and LLC-PK1 cells, and to a lesser extent, human intestinal Caco-2 cells. Whole genome sequencing revealed that the genome of PHEV JS-2025 was 30 044 bp in length, with over 94.9% nucleotide sequence identity to 14 reference PHEV strains, clustering within the rvPHEV-L-1 lineage. Of note, a mutation in the NS2 gene caused a premature termination at amino acid 19, resulting in the functional loss of the NS2 protein. Conclusion A novel PHEV strain JS-2025 from Jiangsu Province was successfully isolated and identified. This strain exhibits unique cellular tropism and can infect human intestinal cell lines, showing a risk of cross-species transmission. The truncated NS2 gene may affect the pathogenic mechanism of this strain. This study aids in understanding the genetic evolutionary characteristics and epidemiological features of PHEV and has implications for the prevention and control of PHE.

Objective To confirm the function of the farnesyl diphosphate (FPP) cyclase encoded by orf2064 in Streptomyces exfoliatus UC5319. Methods orf2064 was expressed in Escherichia coli, and the recombinant protein was purified and assayed with FPP as the substrate. The reaction products were detected by GC-MS. An FPP-overproducing E. coli strain was engineered for heterologous expression of orf2064. The fermentation products were analyzed by GC-MS, and the target compound was isolated and structurally characterized by nuclear magnetic resonance spectroscopy (NMR). In addition, orf2064 was heterologously expressed in Streptomyces, and the fermentation products were analyzed by GC-MS. Results GC-MS revealed that both the in vitro reaction of the recombinant protein ORF2064 and the heterologous expression products in E. coli and Streptomyces consistently produced a compound with identical retention time and [M⁺] of m/z 204. Subsequent isolation, purification, and NMR analysis confirmed this compound as calarene. Conclusion The FPP cyclase encoded by orf2064 in S. exfoliatus is identified as an calarene synthase.