Mycobacterium tuberculosis is the main pathogen causing tuberculosis, and its complex secretion system plays a key role in the pathogenic process. In recent years, the ESX-4 secretion system has attracted much attention. This paper introduces the ESX-4 secretion system from the structures and evolution of its coding genes, protein composition and functions, substrate recognition and transport mechanisms, and transcriptional regulation. It focuses on how the ESX-4 secretion system guides the secretion functions of other ESX secretion systems, and its physiological functions in regulating the death of host cells and participating in iron utilization. On this basis, the analysis of existing studies reveals that ESX-4 secretion system may be involved in the secretion of protein tyrosine phosphatase A (PtpA), a key virulence protein of Mycobacterium tuberculosis. Finally, this paper makes an outlook on the future research directions of the secretory system, aiming to provide some reference for in-depth study of the function of the secretory system and for drug design and vaccine development targeting the secretory system.

Porcine reproductive and respiratory syndrome (PRRS) is a major infectious disease in the swine industry, posing a severe threat to global pig farming. Host microRNAs (miRNAs) are endogenous small non-coding single-stranded RNAs that regulate various biological processes, including cell development, metabolism, apoptosis, and immune responses, by binding to specific target genes. Studies have demonstrated that miRNAs participate in the regulation of viral infection and replication through both direct and indirect mechanisms. This review focuses on the molecular mechanisms by which miRNAs modulate porcine reproductive and respiratory syndrome virus (PRRSV) replication and host innate immune responses during infection, aiming to provide insights for the development of miRNA-based applications and strategies for PRRS control.

Blue carbon ecosystems, including mangroves, salt marshes, seagrass meadows, and macroalgal beds, cover less than 0.5% of the global ocean surface yet account for approximately 50% of carbon burial in marine sediments. These ecosystems play a critical role in the global carbon cycle and climate change. Photosynthetic microorganisms, ubiquitous across blue carbon habitats, participate in biogeochemical cycles of carbon, nitrogen, and phosphorus and are indispensable for ecosystem functionality. This review synthesizes current knowledge on the diversity of these photosynthetic microorganisms in blue carbon ecosystems, their mechanisms of carbon fixation and sequestration, and their ecological interrelationships with macrophytes. Effective management of photosynthetic microorganisms in blue carbon ecosystems is essential to optimizing the ecosystem service. Drawing from the perspectives of controlling harmful photosynthetic microorganisms and nutrient management, this review outlined regulatory strategies aimed at enhancing carbon sequestration. Future studies should consider assessing the impacts of photosynthetic microorganisms on blue carbon ecosystems in the context of climate change. Furthermore, prevention and control strategies should be explored to mitigate the negative effects of these microorganisms on ecosystem service functions.

d-amino acids (d-AAs) the optical isomers of l-amino acids (l-AAs), are extensively involved in host physiological and pathological processes, such as nervous system regulation, renal function maintenance, and inflammatory bowel disease development. d-AAs in the human body primarily originate from gut microbiota metabolism, and their biosynthesis mainly depends on bacterial amino acid racemases (AARs). These enzymes catalyze the stereoisomeric conversion of l-AAs to d-AAs. The generated d-AAs regulate key processes, such as bacterial cell wall remodeling, biofilm formation, and spore germination, thereby influencing the environmental adaptability and pathogenicity of bacteria. This review systematically summarizes bacterial systhesis of d-AAs and the role of AARs. It focuses on the advancements in research regarding production of d-AAs by gut microbiota and interactions with the host, thereby providing a theoretical foundation for disease intervention and therapy targeting microbe-host metabolic dialogues.

Squalene, a natural bioactive compound, has broad applications in pharmaceuticals, cosmetics, and food industries. Traditionally, it is extracted from deep-sea shark liver oil and certain vegetable oils, but these sources face major challenges, including ecological impact, resource limitations, and high extraction costs. In contrast, microbial fermentation offers a sustainable alternative with shorter production cycles, stable yields, and environmental benefits. However, native microbial strains often suffer from limited precursor availability and restricted metabolic flux through the squalene biosynthetic pathway. Recent advances in metabolic engineering have markedly improved squalene production by fine-tuning microbial metabolic networks and optimizing catalytic enzyme systems, providing both a theoretical framework and a practical route for industrial application. This review summarizes the squalene biosynthetic pathway, the characteristics of natural producer strains, and key metabolic engineering strategies-including pathway enhancement, inhibition of competing pathways, cofactor optimization, heterologous expression, and other regulatory approaches. It also discusses current challenges in balancing metabolic flux and reducing production costs, and outlines future perspectives to guide the efficient biosynthesis and large-scale industrial production of squalene.

Medicinal plant inductive endophytes are a special group of plant endophytes, including fungi, bacteria, and actinomycetes, which are widely distributed in the tissues and cells of medicinal plants. These microbes exhibit the function of inducing or promoting medicinal plants to produce new compounds, or accelerating the accumulation of active ingredients in medicinal materials. However, improper preservation can easily lead to strain degeneration, making it difficult to utilize them stably for a long time. This review summarizes the global research progress on medicinal plant-inducing microbes and the current status of their preservation, laying a foundation for the preservation and application of these microbes.

Background In situ product removal (ISPR) alleviates product inhibition by continuously extracting target metabolites during fermentation, thereby markedly increasing the yields. As a high-value fine chemical, trans-2-decenoic acid is susceptible to severe product inhibition effects caused by its rapid intracellular accumulation during fermentation.Objective We employed ISPR to selectively remove trans-2-decenoic acid from the fermentation broth and optimized the resin selection, adsorption-desorption protocols, and reactor design, aiming to overcome product-inhibition bottlenecks and improve both the substrate conversion and titer.Methods We compared nine alkaline anion-exchange resins for their adsorption capacity toward trans-2-decenoic acid and the substrate decanoic acid to identify the best resin. A semi-continuous system coupling peristaltic pumps with ion-exchange columns was constructed, and anhydrous ethanol was employed as the desorption solvent. The ISPR process was scaled to a 10-L bioreactor, and the product dynamics was monitored.Results D303 resin exhibited the highest trans-2-decenoic acid adsorption (276.5 mg/g) and the lowest decanoic acid adsorption (70.8 mg/g), demonstrating high efficiency and excellent selectivity. After autoclaving at 121 ℃ for 20 min, D303 retained 261.2 mg/g adsorption capacity for trans-2-decenoic acid-only 3.79% loss-meeting industrial requirements. Two-step ethanol elution achieved 91.2% recovery. Upon application of ISPR, the titer of trans-2-decenoic acid after 144 h of fed-batch fermentation reached 2.195 g/L, representing a 31.8% increment over that of the conventional substrate-feeding process (1.667 g/L) and a 16.6% increment over that of the conventional medium-feeding process (1.883 g/L).Conclusion Resin-mediated ISPR effectively mitigates product inhibition of trans-2-decenoic acid, boosts the substrate conversion and titer, and enables robust continuous fermentation. This approach offers an innovative and scalable solution for producing high-value organic acids, demonstrating a promising application prospect in engineering.

Background Chiral aromatic heterocyclic alcohols are crucial intermediates in pharmaceutical synthesis. However, the efficient and asymmetric production remains challenging due to the inherent structural constraints of bulky substituents and high symmetry in aromatic heterocyclic ketones, which lead to poor stereoselectivity and substrate adaptability in conventional catalytic systems. Hence, developing enzymes for the stereoselective synthesis of chiral aromatic heterocyclic alcohols is of special interests.Objective This study aims to discover stereocomplementary carbonyl reductases and enhance the catalytic performance of enzymes by a semi-rational design-based engineering strategy for efficient synthesis of (R)- and (S)-2,3-dihydrobenzo thiophene-3-ol(2a).Methods Through systematic screening of our in-house enzyme library, we identified stereocomplementary carbonyl reductases from Rhodococcus erythropolis (ReADH) and Debaryomyces hansenii (DhCR). Rational molecular engineering was conducted to improve the stereoselectivity of DhCR with poor catalytic performance, followed by enzymatic characterization and application in asymmetric synthesis of chiral aromatic heterocyclic alcohols.Results The wild-type enzymes ReADH and DhCR exhibited exceptional enantioselectivity of >99% (R) and 92% (S), respectively, toward benzothiophen-3(2H)-one (1a). Through rational engineering, the mutant DhCR_V227F was obtained, with enhanced e.e. value from 92% to 99%. Enzymatic characterization revealed that the optimal reaction conditions of ReADH were pH 6.0 and 40 ℃ and those of DhCR_V227F were pH 6.5 and 35 ℃. Both enzymes demonstrated broad substrate profiles, including sulfur/oxygen- containing heterocyclic ketones, cyclic ketones, and aryl ketones. Notably, they maintained>99% stereoselectivity at different substrate concentrations in preparative-scale synthesis, and enantiomerically pure (R) and (S)-2a products were synthesized.Conclusion This study provides efficient stereocomplementary biocatalysts ReADH and DhCR_V227F for the asymmetric reduction of aromatic heterocyclic ketones.

Background Kynurenine aminotransferases (KATs) are key enzymes in the kynurenine pathway, and the specific function of KATs in the growth, development, and pathogenic process of Botrytis cinerea is still unclear.Objective To clarify the function of the kynurenine aminotransferase BcKATL10 in the growth, development, and pathogenic process of B. cinerea, and lay a foundation for elucidating the function and mechanism of KATs in the growth, development, and pathogenic process of B. cinerea.Methods We employed bioinformatics tools to analyze the expression level of BcKATL10 in the conidial development stage and infection process of B. cinerea. The knockout mutants ΔBcKATL10 and the overexpression strain BcKATL10-OE of BcKATL10 were constructed by gene knockout and overexpression technologies, respectively. The phenotype and pathogenicity of the mutants and overexpression strain were analyzed with the wild-type strain as a reference.Results The expression level of BcKATL10 was up-regulated during conidial development and infection. Compared with the wild-type strain, ΔBcKATL10 showcased significantly accelerated growth, significantly increased length and width of the mycelial cells, and significantly enhanced pathogenicity. BcKATL10-OE showed significantly slow growth, reduced length and width of the mycelial cells, and no significant difference in the pathogenicity compared with the wild type.Conclusion The kynurenine aminotransferase BcKATL10 negatively regulates the growth, development, and pathogenicity of B. cinerea.

Background The low temperature in Inner Mongolia cool regions constrains the microbial degradation efficiency of maize straw. Although diverse cool adapted microbial communities are present, their succession patterns and functions roles remain unclear.Objective We investigated the succession patterns and functional characteristics of microbial communities in maize straw under low-temperature (15 ℃) fermentation conditions, aiming to reveal the interaction mechanisms between bacteria and fungi and provide theoretical support for the utilization of straw resources and the development of low-temperature microbial agents.Methods We constructed the low-temperature fermentation system and collected samples at stages (SD1-SD4, every 15 days). Illumina NovaSeq 6000 was employed to analyze the diversity, composition, and interaction networks of bacterial and fungal communities. Linear discriminant analysis effect size (LEfSe) and correlation networks were used to identify key functional microbial groups.Results The number of bacterium-specific OTUs gradually increased over fermentation time, while fungus-specific OTUs showed a “decrease-increase-decrease” trend. The relative abundance of Pseudomonadota, Bacteroidota, and Actinomycetota exhibited a “decrease-increase” trend. Bacteroidota was dominant at the early stage, followed by significant enrichment of Actinomycetota. The fungal community was dominated by Ascomycota and Zygomycota. At the genus level, Sphingobacterium, Enterobacter, and Rhodanobacter were the dominant bacteria at different stages, while Phaeoacremonium, Mycothermus, and Fusarium exhibited stage-specific succession within the fungal community. LEfSe results showed that Chloroflexota and Corynascus were the key functional bacteria that distinguished SD3 from other stages. The fermentation products of the compound microbial system increased the activity of antioxidant enzymes and enhanced the saline-alkali stress tolerance of maize seedlings.Conclusion During fermentation, the microbial community displayed significant staged succession, and bacteria and fungi formed synergistic effects through the functional relay mode to promote the straw fermentation process in cool areas.

Background Anthracnose is one of the major diseases attacking Panax quinquefolius in northeast China, leading to declined quality and yield and causing severe economic losses of P. quinquefolius. Objective To screen out a biocontrol strain with inhibitory effects on Colletotrichum panacicola, providing a theoretical basis for the development of biocontrol agents. Methods We employed the plate confrontation method to screen out the biocontrol strain Y510-8 with high antagonistic activity against C. panacicola. Morphological, physiological, biochemical, and molecular evidence was collected for strain identification, and the extracellular enzyme-producing abilities of the strain was determined. Through field experiments, the effects of the biocontrol strain on C. panacicola and the growth of P. quinquefolius in practical applications were determined. Results A strain Bacillus velezensis Y510-8 with high inhibitory activity against C. panacicola was screened out, and its inhibition rate was as high as 93.48%. The strain had the abilities to produce cellulase, amylase, protease, and siderophores, solubilize potassium, and fix nitrogen. It promoted the growth and curbed the anthracnose spread of P. quinquefolius. The strain increased the relative abundance of beneficial bacterial communities in the soil, while decreasing the relative abundance of Ilyonectria and Fusarium. Conclusion B. velezensis Y510-8 has an inhibitory ability against C. panacicola and the potential to promote the growth of P. quinquefolius. The findings lay a theoretical foundation for the development of the strain into a biocontrol agent.

Background Trichoderma harzianum WF2 was isolated in our laboratory. It has excellent biocontrol effects on many tobacco diseases and can induce plant disease resistance, demonstrating a promising application prospect.Objective To optimize the fermentation conditions of T. harzianum WF2 for improving the yield of chlamydospores, providing a technological basis for the industrial production of this strain. In addition, the changes of the microbial community structure in the rhizosphere soil of tobacco after the application of the fermentation liquid of T. harzianum WF2 chlamydospores were analyzed.Methods The fermentation conditions were optimized by single factor experiments and the fermentation medium was optimized by the response surface methodology. The optimized fermentation product was verified by a pot experiment for biocontrol effect. The tobacco rhizosphere soil samples treated with WF2 chlamydospore fermentation broth were collected, and the community diversity and composition of rhizosphere microorganisms were analyzed by amplicon sequencing based on 16S rRNA gene and ITS region. The PICRUSt2 and FUNGuild databases were used to predict and analyze microbial functions.Results The optimum fermentation conditions were as follows: 25 ℃, 240 r/min, initial pH 4.0, an inoculation amount of 3%, and a liquid volume of 60 mL. The optimum fermentation medium was composed of 15.00 g/L glucose, 15.00 g/L sorghum powder, 19.61 g/L corn steep liquor, 1.25 g/L ammonium sulfate, 1.00 g/L magnesium sulfate, 1.00 g/L calcium carbonate, 1.00 g/L zinc sulfate, and 1.00 g/L potassium dihydrogen phosphate. Under these conditions, the yield of chlamydospores was the highest, reaching 5.16×10⁷ CFU/mL. The pot experiment showed that the biocontrol effects of chlamydospore dilution at 1×10⁷ CFU/mL on tobacco black shank and tobacco root rot were 87.33% and 81.00%, respectively. The application of WF2 chlamydospore fermentation liquid significantly increased the bacterial diversity and richness, while reducing the fungal diversity and evenness. In addition, the fermentation liquid increased the relative abundance of beneficial bacteria while reducing the relative abundance of harmful fungi.Conclusion The fermentation formula for the high yielding of chlamydospores is obtained by fermentation condition optimization. The application of the fermentation liquid significantly reduces the disease indexes of tobacco black shank and tobacco root rot. At the same time, it improves the microbial community structure in tobacco rhizosphere soil by increasing the relative abundance of beneficial bacteria and reducing the relative abundance of plant pathogenic fungi.

Background Plant growth-promoting rhizobacteria (PGPR) exhibit low abundance in saline-alkali soils, which limits their application in saline-alkali farmlands. Saline-alkali-tolerant PGPR, with strong adaptability and stability in high-salinity environments, have gradually become key microbial resources for the remediation of saline-alkali soils.Objective To screen rhizosphere microorganisms with saline-alkali tolerance and plant growth-promoting functions and evaluate their regulatory effects on maize growth under salt stress, providing a scientific basis for improving the quality of saline-alkali farmlands and the application of agricultural microorganisms in arid and semi-arid regions.Methods Four bacterial strains—Metabacillus litoralis LS08, Bacillus atrophaeus LS11, Achromobacter denitrificans LS13, and Lysinibacillus fusiformis YJM01—isolated from plant roots in saline-alkali soils of Ningxia were selected. Their salt-alkali tolerance and growth-promoting functions were assessed, and their regulatory effects on maize seed germination, seedling growth, and photosynthetic performance were evaluated under gradient salt stress conditions (0-0.9% NaCl).Results All the four PGPR strains exhibited strong saline-alkali tolerance and at least three plant growth-promoting functions. Among them, LS08 showed the highest potassium solubilization capacity, and LS11 demonstrated the strongest abilities in inorganic phosphorus solubilization, nitrogen fixation, and siderophore production. LS13 excelled in organic phosphorus solubilization, and YJM01 exhibited outstanding capabilities in indole-3-acetic acid (IAA) production and urease activity. Under salt stress, the application of these four strains significantly enhanced maize seed germination, seedling growth, and photosynthetic performance. Membership function and correlation analyses indicated that LS11 had the most significant growth-promoting effect on maize seedlings under salt stress. This strain significantly improved maize salt tolerance by enhancing seed germination quality (increasing the germination rate by 0.5 to 13.5 times), boosting photosynthetic efficiency (increasing the net photosynthetic rate by 0.6 to 2.1 times), and promoting biomass accumulation (increasing the dry and fresh weights by 30.9%-56.3% and 35.2%-69.5%, respectively).Conclusion The four saline-alkali-tolerant PGPR strains screened in this study all demonstrated favorable growth-promoting effects on maize under salt stress. Among them, the strain LS11 exhibited the most outstanding performance in enhancing maize salt tolerance and can be considered a high-quality microbial resource for developing bacterial fertilizers for saline-alkali soils.

Background Continuous cropping obstacles have severely hindered the healthy development of the Angelica sinensis cultivation industry, making the development of compound microbial agents to enhance the quality of this medicinal plant an urgent priority.Objective We investigated the effects of foliar spraying with disease resistant and non-disease-resistant composite microbial agents on the quality of A. sinensis under continuous cropping conditions, aiming to provide a theoretical basis for developing more effective disease-resistant and growth-promoting compound microbial agents.Methods Bacterial strains were isolated via the dilution plate coating method and identified through morphological observation combined with molecular techniques. Conventional methods were employed to determine the physiological and biochemical characteristics of the strains, as well as to evaluate the growth and disease incidence of A. sinensis. The content of bioactive compounds in A. sinensis roots was quantified by HPLC. Commercial assay kits were used to measure the plant physiological and biochemical parameters, along with strain-related enzyme activities. Endogenous hormone metabolites were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry with multiple reaction monitoring (UPLC-MS/MS+MRM).Results A total of six bacterial strains exhibiting growth-promoting effects on A. sinensis were screened out. According to their antagonistic activity against Fusarium solani, they were classified into two groups: the antagonistic strain (KJ) group consisting of Bacillus velezensis, B. amyloliquefaciens, and B. atrophaeus and the non-antagonistic strain (BJ) group comprising Brevibacillus laterosporus, Peribacillus frigoritolerans, and B. megaterium. Field foliar spraying experiments were conducted with the compound agents developed with these strains. Both KJ and BJ treatments promoted A. sinensis growth, alleviated soil-borne diseases, and enhanced the accumulation of active components. Compared with the control (CK), the KJ treatment increased the fresh weight per 100 plants by 29.69% and reduced the root rot incidence by 69.44% (P<0.05). The BJ treatment increased the fresh weight per 100 plants by 47.97% and reduced the root rot incidence by 25.00% (P<0.05). Compared with CK, the KJ treatment increased the malondialdehyde (MDA), nitrite reductase, ammonium nitrogen, net photosynthetic rate (Pn), and transpiration rate (Tr), but decreased the DPPH radical scavenging activity, nitrate reductase, glutamine synthetase, soluble sugars, and chlorophyll content of leaves (P<0.05). The BJ treatment enhanced the MDA, peroxidase activity, total phenols, flavonoids, glutamine synthetase, ammonium nitrogen, Pn, and Tr of leaves (P<0.05). Additionally, the KJ treatment significantly raised the cytokinin and salicylic acid levels while lowering the jasmonic acid and gibberellin levels compared with CK. The BJ treatment significantly elevated the abscisic acid, auxin, cytokinin, gibberellin, and 12-oxo-phytodienoic acid levels.Conclusion Both the KJ agent composed of B. velezensis, B. amyloliquefaciens, and B. atrophaeus and the BJ agent consisting of B. laterosporus, Peribacillus frigoritolerans, and B. megaterium demonstrate disease-resistant and growth-promoting effects on A. sinensis. The KJ agent effectively controls diseases under Fusarium stress but incurs oxidative toxicity costs. The KJ agent may be more adaptable to complex environments and enhances plant growth and defense potential by optimizing the physiological functions of A. sinensis.

Background Endophytic nitrogen-fixing bacteria in plants are capable of converting atmospheric nitrogen into nitrogenous compounds that can be absorbed by plants, providing a sustainable source of nitrogen for plant growth.Objective This study aims to investigate the growth-promoting effects of the nitrogen-fixing bacterium Curtobacterium sp. A02 isolated from cassava roots on leafy vegetables and develop its lyophilized agent.Methods A pot experiment was conducted to apply the nitrogen-fixing bacterium A02 to pak choi (Brassica rapa var. chinensis) and lettuce (Lactuca sativa var. longifolia) through root inoculation. Agronomic traits, biomass, nitrogen accumulation, and activities of nitrogen metabolism-related enzymes of the treated plants were measured. The culture conditions for high-density proliferation of strain A02 were optimized by single-factor experiments and Box-Behnken design with response surface methodology, and a lyophilized bacterial agent was developed.Results The inoculation with strain A02 significantly increased the biomass, plant height, and root length of the vegetables. It increased the total biomass of pak choi by 20.5-25.7 times and that of lettuce by 33.6-34.4 times. Optimization of culture conditions for high-density and low-cost proliferation increased the viable cell count of strain A02 by 20.24 times. The developed lyophilized agent of A02 had a survival rate of 86.9% after 4 weeks.Conclusion The cassava endophytic nitrogen-fixing bacterium A02 has significant growth-promoting effects on vegetables and shows potential for development into a lyophilized bacterial agent.

Background Fusarium wilt caused by Fusarium oxysporum is a devastating soil-borne disease affecting vegetables such as cucumber (Cucumis sativus L.) and tomato (Solanum lycopersicum L.). Its formae speciales invade vascular systems, leading to plant wilting and death and causing the global annual yield losses of 20%-50%. Current disease control strategies relying heavily on chemical fungicides face challenges, including the persistent development of pathogen resistance, disruption of soil microecosystems, and increased risks of fungicide residues. These issues pose substantial threats to vegetable quality and human health.Objective Rhizosphere microorganisms represent a natural reservoir for disease suppression. The mining of antagonistic bacteria from this reservoir is a crucial direction for eco-friendly control strategies. This study aimed to screen the bacterial strains with high antagonistic activity against F. oxysporum from the rhizosphere soil of cucumber and tomato plants intercropped with potato-onion. We further constructed a synthetic community (SynCom) and evaluated its biocontrol efficacy and plant growth-promoting effects, aiming to provide novel microbial resources for the eco-friendly control of Fusarium wilt.Methods A total of 505 rhizosphere bacterial isolates were preliminarily screened by the dual-culture plate method. Strains exhibiting an inhibition rate >50% were selected for further study. Strain identification was performed based on morphological observation, physiological and biochemical tests, and 16S rRNA gene phylogenetic analysis. PCR was employed to detect the genes involved in antibiotic synthesis. Plant growth-promoting effects, including indole-3-acetic acid (IAA) production, phosphate solubilization, siderophore production, and biofilm formation were assessed. A SynCom was constructed based on compatibility assays. Pot experiments were conducted to investigate the effects of the SynCom on the seedling growth and Fusarium wilt in cucumber and tomato.Results Three highly efficient antagonistic strains were selected. HB1 was identified as Bacillus amyloliquefaciens, HB5 as B. velezensis, and HB15 as B. tequilensis. The three strains exhibited inhibition rates of 60.04%, 57.15%, and 61.41% against F. oxysporum f. sp. cucumerinum and 56.22%, 57.07%, and 58.03% against F. oxysporum f. sp. lycopersici. All the three strains possessed the antibiotic biosynthesis genes bmyB, fenD, and srfAA. Additionally, HB1 and HB5 carried ituC. All the strains demonstrated multiple plant growth-promoting effects: IAA production, phosphate solubilization, siderophore production, biofilm formation, cellulase production, and protease production. HB15 exhibited the highest potential for plant growth promotion and biocontrol (IAA production: 70.88 mg/L; phosphate solubilization: 68.84 mg/L; solubility index: 79.90%). No antagonism was observed among the three strains, and their co-culture significantly enhanced mutual growth. The SynCom constructed with these three strains significantly increased the stem diameter, plant height, and biomass of cucumber and tomato seedlings by 11.11% to 75.79%. Moreover, it activated plant defense enzymes, achieving the disease control efficacy of 57.90% to 67.02%.Conclusion The SynCom composed of HB1, HB5, and HB15 synergistically achieved efficient control of Fusarium wilt in both cucumber and tomato plants, while promoting plant growth. This was accomplished through the cooperative secretion of antibiotics and the activation of plant defense enzymes and multiple plant growth-promoting effects. This study provides a theoretical foundation for developing multifunctional microbial inoculants.

Background The low activity of amylases in industrial pectinase reagents leads to unsatisfactory results in the production of fruit juice rich in starch. However, there are few reports that using amylases alone can improve the quality of fruit juice rich in starch in multiple aspects.Objective To obtain amylases capable of increasing the quality of banana juice in multiple aspects.Methods Targeted screening was employed to obtain the microorganisms producing acidic amylases. We determined the enzymatic characteristics to primarily assess the compatibility of the amylases with the current industrial process for fruit juice production and then applied the amylases in banana juice production to evaluate the application potential of the amylases.Results Fungal strains TYJF2 and TYJF14 producing amylases were screened from soil and identified as Aspergillus ostianus and Aspergillus cerealis, respectively, by morphological characterization and internal transcribed spacer sequence comparison. Both crude amylases of TYJF2 and TYJF14 showed optimal pH 5.5 and the relative activities higher than 90% after incubation at pH 5.5-7.0 for 24 h. The crude amylases of TYJF2 and TYJF14 showed an optimal temperature at 50 ℃ and the relative activities of (25.37±2.60)% and (89.32±1.77)% after incubation at 50 ℃ for 1 h, respectively. The activities of the crude amylases of TYJF2 and TYJF14 were promoted by 1 mmol/L and 2 mmol/L Ca²⁺ and inhibited by 2 mmol/L and 5 mmol/L Na₂EDTA. The activities of crude amylases of TYJF2 and TYJF14 were not affected by K⁺, Li⁺, or Zn²⁺ at 1, 2, and 5 mmol/L. The addition of 0.30 U/mL crude amylases of TYJF2 and TYJF14 increased the yield of banana juice by (13.00±0.76)% and (11.67±1.00)%, the clarity by (26.68±1.24)% and (22.79±0.18)%, and the content of reducing sugar by (18.30±1.32)% and (23.08±0.51)%, respectively.Conclusion The crude amylases of TYJF2 and TYJF14 demonstrate the enzymatic characteristics meeting the requirement of the current industrial fruit juice production process and improve the quality of banana juice in multiple aspects, showing potential in the juice production using fruits rich in starch.

Background Mastitis poses a serious threat to the dairy cow industry, and the abuse of broad-spectrum antibiotics has led to a notable rise in fungal mastitis cases. Studies on the isolation and biological characterization of pathogenic Candida spp. remain limited.Objective To identify and characterize a fungal pathogen isolated from mastitis cases in Tongliao, Inner Mongolia and evaluate its biological traits and pathogenic potential, thus informing clinical control strategies.Methods The Sabouraud dextrose agar (SDA) was used for strain isolation, which was followed by Gram staining for morphological observation. Preliminary identification employed CHROMagar^TM Candida Chromogenic Medium, with confirmatory molecular analysis through sequencing of the ITS region and six housekeeping genes (ICL1, SAPT2, SAPT4, XYR1, ZWFla, and MDR1). Virulence profiling included measurement of phospholipase activity (PZ value) via yolk agar assay, determination of hemolysis (HI index) on sheep blood agar, and quantification of biofilm formation (OD₅₇₀) by crystal violet staining. Biofilm-associated genes (BCR1, EFG1, TEC1, UME6, ALS1, and ALS3) were detected by RT-qPCR. A murine infection model was established to assess the pathogenicity, while antifungal susceptibility testing followed CLSI guidelines for five agents: caspofungin (CAS), amphotericin B (AMB), nystatin (NYS), voriconazole (VOR), and fluconazole (FLC).Results The isolate, designated Candida tropicalis TLN2023, exhibited moderate phospholipase activity (PZ=0.626) but no hemolysis. It demonstrated strong biofilm formation and harbored all the six biofilm-related genes. Murine challenge confirmed its pathogenicity. Antifungal testing revealed susceptibility to CAS and AMB and resistance to triazoles (VOR and FLC).Conclusion We successfully isolated and characterized C. tropicalis TLN2023, a triazole-resistant pathogen with multiple virulence factors, from mastitis cases of dairy cows in Inner Mongolia. The isolate demonstrated significant biofilm-forming capacity and a distinct drug-resistance profile, which highlighted the urgent need for enhanced fungal surveillance programs and more judicious application of antifungal agents in pasture management systems.

Background Neodon fuscus, an endemic vole species of the Qinghai-Xizang Plateau in China, garners considerable interest due to its potential role as a vector for pathogens, while the research on wild vole populations in Qinghai remains limited.Objective To characterize the microbial community composition and identify potential pathogens carried by N. fuscus in Gandé (GD) and Yushu (YS) with different altitudes.Methods We employed metagenomic sequencing and genome assembly techniques to comprehensively analyze the intestinal microbiota and identify the pathogens present in wild N. fuscus.Results Metagenomic analysis of voles collected from GD and YS revealed that Bacillota, Bacteroidota, Actinomycetota, Thermodesulfobacteriota, Spirochaetota, and Pseudomonadota were dominant in the intestinal microbiota in both sampling regions, indicating the intestinal microbiota was highly conserved at the phylum level. However, significant differences in dominant species and overall community structure were observed between voles from GD and YS. Notably, the microbial diversity of GD voles was significantly higher than that of YS voles, suggesting that geographical and environmental factors exerted considerable influences on the intestinal microbiota composition of N. fuscus. Through metagenome-assembled genomes (MAGs), several potential pathogenic bacteria were identified in the intestinal microbiota, including Klebsiella spp., Streptococcus spp., Pseudomonas spp., Staphylococcus spp., and Pasteurella spp. Furthermore, Ectromelia virus, Toxoplasma gondii, Encephalitozoon cuniculi, Encephalitozoon hellem, Encephalitozoon intestinalis, and Encephalitozoon romaleae were detected in N. fuscus from both regions. KEGG analysis indicated that the intestinal microbiota of N. fuscus exhibited abundant metabolic pathway genes, with carbohydrate metabolism being the most prominent subcategory, highlighting the crucial role of the intestinal microbiota in vole metabolism.Conclusion This study demonstrates significant variations in the intestinal microbiota structure of N. fuscus at different altitudes and confirms the presence of potential pathogenic bacteria in all sampled individuals. These findings provide baseline data for comprehensively understanding the microbial diversity and carried pathogens in N. fuscus, thereby contributing valuable scientific evidence for the prevention and control of related zoonotic diseases.

Background Streptococcus pluranimalium is a Gram-positive bacterium belonging to the family Streptococcaceae. It has a wide host range and can infect various animals and humans. Studying its biological characteristics is of great significance.Objective To isolate and study the biological characteristics of Streptococcus pluranimalium.Methods We collected the nasal swabs from bovine suspected of having respiratory symptoms and inoculated them into the BHI+10% FBS liquid medium for bacterial isolation. After culture for 12–16 h, the BHI+10% FBS plate was used for plate streaking. Single colonies were selected and amplified in BHI+10% FBS liquid medium, and then the species was identified by Gram-staining microscopy, 16S rRNA gene sequencing, and biochemical tests. Furthermore, amplification with specific primers, antimicrobial susceptibility tests, and median lethal dose (LD₅₀) determination were conducted on the isolate.Results A strain of S. pluranimalium was successfully isolated. It was Gram-positive and distributed in a short chain pattern. The amplified product of 16S rRNA gene was 1 500 bp in length, and comparison of the sequencing results with the published sequences via NCBI-BLAST confirmed the strain as Streptococcus pluranimalium. The results of biochemical tests showed that the bacterium could ferment sucrose, d-mannose, glucose, d-fructose, and trehalose, while it could not ferment xylose, d-mannitol, d-sorbitol, lactose or rhamnose. The strain showed positive results in peroxidase and VP tests and negative results in methyl red and indole tests. The results of antimicrobial susceptibility tests showed that the strain was sensitive to polymyxin B, cefuroxime sodium, ceftazidime, ciprofloxacin, and vancomycin, and it was intermediate to penicillin, ampicillin, ceftriaxone, cefoperazone, and norfloxacin. It was resistant to 10 antibiotics: gentamicin, kanamycin, streptomycin, tetracycline, erythromycin, azithromycin, cotrimoxazole, chloramphenicol, clindamycin, and levofloxacin, with particularly strong resistance to gentamicin, kanamycin, streptomycin, erythromycin, azithromycin, cotrimoxazole, chloramphenicol, and clindamycin. The strain showed the LD₅₀ of 2.14×10⁷ CFU in the SPF grade BALB/c female mice of 6 to 8 weeks old.Conclusion A strain of Streptococcus pluranimalium was successfully isolated, which was resistant to diverse antibiotics and pathogenic to mice.

Background Bacillus velezensis exhibiting notable stress resistance and antimicrobial activity is listed in the Feed Additive Catalogue of Microbial Species for Animal Use.Objective We characterized the probiotic properties and safety profile of B. velezensis E2 isolated from Kunming dogs based on whole-genome sequencing, aiming to provide a theoretical foundation for its development as a canine-specific probiotic feed additive.Methods B. velezensis E2 was evaluated for acid and bile salt tolerance, cell adhesion capability, enzyme production, antioxidant activity, antimicrobial activity, hemolytic activity, and biogenic amine synthesis. PacBioSequel IIe and Illumina NovaSeq 6000 were used for whole-genome sequencing. The resulting genome was annotated to identify genes associated with probiotic properties and potential virulence factors.Results B. velezensis E2 demonstrated robust tolerance to acids and bile salts, strong adhesion capability, significant antioxidant activity, and potent antimicrobial effects. It produced protease, amylase, and cellulase. Crucially, the strain exhibited no hemolytic activity and produced none of the tested biogenic amines (cadaverine, putrescine, and agmatine). Whole-genome sequencing revealed a circular chromosome of 4 203 905 bp with the G+C content of 45.77%, encoding 4 143 genes. Genome annotation identified the genes linked to key probiotic properties, including acid/bile salt tolerance, adhesion, antioxidant activity, class II lanthipeptide production, and cold/heat stress responses. No virulence genes were detected.Conclusion B. velezensis E2 possesses excellent probiotic properties and a favorable safety profile, serving as a highly promising candidate strain for development as a canine-specific probiotic feed additive.

Background In recent years, the rapid expansion of sheep farming has been accompanied by an increasing incidence of streptococcosis in sheep and goats. This disease has a short incubation period and poses serious risks to the farming industry.Objective We aimed to isolate and identify a strain of Streptococcus ovis from the respiratory tract of Hu sheep, elucidate its genomic features, virulence factors, and antibiotic resistance genes through genome sequencing, and evaluate the inhibitory activities of pomegranate peel against the growth and biofilm formation of this strain.Methods We isolated bacteria from nasal swabs of Hu sheep. The strain was preliminarily identified via morphological observation, Gram staining, and 16S rRNA gene sequencing. We performed whole-genome sequencing with Illumina technology and annotated the genome in the NR, GO, KEGG, COG, VFDB, and CARD databases. We adopted the broth dilution method to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of pomegranate peel. The growth curves were plotted at MIC, 1/2 MIC, and 1/4 MIC of the extract. Furthermore, we employed crystal violet and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays to assess the inhibition and clearance effects of pomegranate peel on the biofilm and viable bacterial count in the biofilm removed.Results The isolate was identified as S. ovis. It had a genome size of 2 206 748 bp (2.21 Mb), with 1 599, 1 208, and 1 997 genes annotated in the GO, KEGG, and COG databases, respectively. We identified 88 virulence genes and 51 antibiotic resistance genes. The pomegranate peel at MIC significantly inhibited the growth of S. ovis, with MIC and MBC of 62.5 mg/mL and 250 mg/mL, respectively. In addition, the pomegranate peel inhibited the biofilm formation (P<0.01), disrupted both initial and mature biofilms (P<0.01), and reduced viable bacterial counts within biofilms (P<0.01). These effects were concentration-dependent within the tested range.Conclusion We successfully isolated and identified a strain of S. ovis and uncovered multiple virulence and antibiotic resistance genes. The pomegranate peel showed significant inhibitory activities against the growth and biofilm formation of this strain. The findings provide a basis for further research into the pathogenesis and resistance mechanisms of S. ovis, as well as the development of herbal agents as alternatives of antibiotics.

Background The Poyang Lake serves as a major wintering ground for important migratory birds such as the Siberian crane (Grus leucogeranus). The health status of these birds is a key indicator for assessing the safety of the local ecosystem. In recent years, increased human activities around the wintering areas have led to the introduction of antibiotics into the environment through medical, agricultural, and aquaculture practices. This may expose the Siberian cranes to antibiotic residues and selective pressure from drug-resistant bacteria, posing a potential threat to their survival and health.Objective This study analyzed the antibiotic resistance characteristics of conditionally pathogenic bacteria in Siberian crane feces and discusses the potential effects of these bacteria on local biological health and ecological safety, aiming to enrich the microbial data of local rare and precious species and provide a basis for biological safety monitoring and ecological health protection.Methods 60 fresh fecal samples were collected from Siberian cranes within the reserve. After enrichment in LB broth, they were inoculated onto MacConkey, Enterococcus-selective, and Staphylococcus-selective media to isolate target strains. Bacteria were identified by colony morphological characterization and PCR. Antimicrobial susceptibility testing was performed via the minimum inhibitory concentration method. PacBio third-generation sequencing was conducted to reveal the whole genomes of multidrug-resistant (MDR) strains.Results A total of 28 (46.67%) Escherichia coli strains, 36 (60.00%) Enterococcus strains, and 13 (21.67%) Staphylococcus aureus strains were isolated. Antimicrobial susceptibility testing revealed that E. coli showed high resistance rates to polymyxin E (57.14%), sulfisoxazole (42.86%), and tetracycline (46.43%). Enterococcus exhibited high resistance rates to ceftiofur (75.00%), cefoxitin (86.11%), oxacillin (88.89%), and sulfisoxazole (80.56%). S. aureus showed high resistance rates to tetracycline (69.23%) and florfenicol (53.85%). Nine E. coli strains, 27 Enterococcus strains, and one S. aureus strain were identified as MDR strains. Genomic sequencing revealed that these multidrug-resistant strains carried various resistance genes. For instance, a pentadrug-resistant Enterococcus faecium strain carried 17 resistance genes.Conclusion The results indicate that bacteria isolated from Siberian crane feces exhibit high resistance rates, with the presence of multidrug-resistant strains carrying diverse resistance genes. These findings enrich the baseline database of drug-resistant bacteria in rare migratory birds and provide important clues for further research on the transmission and fate of resistance genes in the environment.

Background Ascosphaera apis is an obligate parasitic fungal pathogen whose infectivity displays a marked specificity for honeybee larvae, typically resulting in lethal chalkbrood disease. However, the miRNA expression profiles of A. apis during host infection and the functions of their target genes remain largely unexplored. Objective We investigate the expression patterns of ace-miR-2478-y and its target gene steroid hormone receptor ( ERR 1) in the larval gut of Apis cerana cerana during Ascosphaera apis infection, aiming to lay a foundation for elucidating the molecular regulatory mechanisms of ace-miR-2478-y in response to A. apis infection. Methods stem-loop RT-PCR and Sanger sequencing were employed to verify the true expression of ace-miR-2478-y and the accuracy of its sequence in the larval gut before and after inoculation with A. apis. The target mRNAs of ace-miR-2478-y were predicted by bioinformatics software, and the regulatory network of ace-miR-2478-y and its target mRNAs was constructed in Cytoscape. The target mRNA sequences were subjected to homology alignment using the BLAST tool to identify their corresponding genes. Functional annotations and pathway information for these genes were then obtained based on the GO and KEGG databases. The binding relationship between ace-miR-2478-y and ERR 1 was verified by the dual luciferase reporter gene assay. RT-qPCR was employed to determine the relative expression of ace-miR-2478-y and ERR 1 in the guts of larvae inoculated with A. apis. Results The results of stem-loop RT-PCR showed that the target fragment of ace-miR-2478-y was amplified from the guts of A. c. cerana larvae before and after inoculation with A. apis. Sanger sequencing results showed that the fragment sequence was completely consistent with the sequencing results. Ace-mi-2478-y targeted 233 mRNAs, corresponding to 110 target genes. These target genes could be annotated to 23 GO terms such as biological regulation, cell, and binding and 125 KEGG pathways such as the Wnt signaling pathway and protein absorption and digestion. The results of dual luciferase reporter gene assay showed a real binding relationship between ace-miR-2478-y and its target gene ERR 1. RT-qPCR results showed that compared with that in the uninfected group, the expression of ace-miR-2478-y increased significantly at one day post inoculation (dpi) of A. apis and decreased significantly at two dpi and three dpi. The expression of the target gene ERR 1 showed an opposite trend, being significantly down-regulated at 1 dpi and significantly up-regulated at 2 dpi and 3 dpi. Conclusion Ace-miR-2478-y responded to the infection of A. apis by negatively regulating the expression of the target gene ERR 1. The results provide a reference for deciphering the mechanism by which A. c. cerana larvae respond to the A. apis infection.

Background Phosphorus and potassium are essential macroelements for plant growth and development. Objective Twelve strains of fungi isolated from mud of ferrophosphorus tailings in Chengde City, Hebei Province were used as materials to screen and identify efficient phosphorus- and potassium-solubilizing strains and explore their phosphorus- and potassium-solubilizing ability. Methods The target strains were obtained by the preliminary screening for the solubilization ability of insoluble phosphorus and potassium and the re-screening for soluble substance production in liquid fermentation. The phosphorus solubilization mechanisms of the target strains were explored. Results The soluble phosphorus and potassium content in the supernatant of strain KNF-09 were the highest (466.17 mg/L and 414.61 mg/L) on the 4th day in the phosphorus-solubilizing and potassium-solubilizing media, respectively. Meanwhile, strain KNF-09 alleviated the stress of soluble phosphorus/potassium deficiency on lettuce seedlings and significantly increased the fresh weight of lettuce. Conclusion A Talaromyces strain with phosphorus- and potassium-solubilizing activities was isolated from ferrophosphorus tailings, which had potential to be developed into a phosphorus- and potassium-solubilizing microbial fertilizer.

Background In southern China where the soil is acidic, after the late rice harvest, straw is often disposed by burning, which leads to resource waste and environmental pollution.Objective To achieve the utilization of straw resources, we need to overcome the low-temperature limitations of straw incorporation and promote the rapid degradation of late rice straw under low-temperature and acidic soil conditions.Methods The decayed soil from the bottom of rice straw stacks that had been piled up for several years was used as material. An enrichment medium was used to isolate psychrotrophic acid-tolerant strains with lignin-degrading capabilities. Single-factor experiments and response surface methodology were employed to study the enzyme production characteristics of the strains. The effects of cultivation conditions such as time, pH, temperature, and inoculum size on the degradation performance, biomass, and enzyme activity of psychrotrophic acid-tolerant lignin-degrading strains were clarified.Results The degradation performance, biomass, and enzyme activity of these strains reached the highest levels in the case of the cultivation time of six days, pH 6, cultivation temperature of 15 ℃, and inoculum size of 2%. The response surface methodology was employed to optimize the cultivation conditions.Conclusion The results of this study provide a theoretical basis for promoting the degradation of lignocellulose under low-temperature and acidic conditions and achieving the utilization of straw resources.

Background The cultivated strains of Pleurotus pulmonarius in China have low genetic diversity and a narrow genetic background.Objective To develop new elite cultivars that meet market demands based on the germplasm resources of wild P. pulmonarius.Methods We isolated a pure strain ‘SX2’ through tissue culture from a Pleurotus fruiting body collected in Xizang Autonomous Region. The strain was identified based on morphological characteristics and ITS sequence. A single-factor biological characteristic experiments of the strain ‘SX2’ was conducted from five aspects: carbon source, nitrogen source, inorganic salt, growth factor, and temperature. Three relatively optimal levels were selected for orthogonal experiments. The genetic diversity of the strain was analyzed with inter-simple sequence repeat (ISSR) molecular markers. Finally, a domestication experiment was conducted on this strain.Results The single-factor experiment results of strain ‘SX2’ indicated that the optimal culture conditions for the mycelial growth were 25 ℃, carbon sources of brown granulated sugar, sucrose, and maltose, nitrogen sources of yeast extract, beef extract, and peptone, inorganic salts of K₂HPO₄, K₂SO₄, and MgSO₄, and suitable growth factors of nicotinic acid, vitamin B₆, and vitamin B₁. The results of the orthogonal experiments indicated that the optimal culture medium was composed of 20.0 g/L brown granulated sugar, 2.0 g/L yeast extract powder, 2.0 g/L KH₂PO₄, and 0.1 g/L nicotinic acid. Genetic diversity research indicated that there were significant differences between ‘SX2’ and other cultivars of P. pulmonarius. Domestication results indicated that mycelium cultivation can be completed in 28–30 days under conditions of 23–25 ℃ and darkness. After the temperature was adjusted to 26–28 ℃ for post-maturation cultivation, mycelium cultivation was completed in 10 days. The temperature in the fruiting body cultivation was set at 4–8 ℃, and bags were opened after 10–12 hours of cold stimulation. Under conditions with the temperature range of 20–22 ℃ and the air relative humidity of 85%–95%, the primordia can be formed in 3–4 days, and it only took about three days for primordia to differentiate into mature fruiting bodies.Conclusion P. pulmonarius ‘SX2’ possesses biological characteristics distinct from the currently commercial cultivars, such as early maturity and a high yield, thus holding significant potential for development and utilization.

Background As an important ecological functional area in northeast China, the Changbai Mountain region is rich in macrofungal resources, among which Lyophyllum decastes has garnered significant attention owing to its unique edible and medicinal values.Objective To facilitate the protection and sustainable utilization of the wild strain resources of this species and establish an efficient culture system.Methods We employed a multi-stage optimization strategy to optimize the culture conditions for the wild L. decastes strain isolated from the Changbai Mountain region. The key influencing factors were screened by single factor tests combined with the Plackett-Burman test, and the response surface method was utilized to establish a prediction model to optimize the liquid medium formulas. Additionally, the medium formulas for secondary culture were screened, and the mixture uniform design was adopted to optimize the solid medium formula for tertiary culture.Results The significant factors affecting the liquid culture were glucose, corn flour, and magnesium sulfate. A prediction model was established via the response surface method (R²=0.984 1). The optimal culture conditions were as follows: glucose 26.135 g/L, corn flour 31.074 g/L, and magnesium sulfate 1.517 g/L. Under these conditions, the mycelial biomass was (21.89±0.20) g/L. The mycelial growth rate in the wheat grain medium supplemented with sawdust for secondary culture reached (2.62±0.38) mm/d. The optimal medium formula for the tertiary culture was composed of 24% corncob, 43% sawdust, and 33% cotton seed hull. The mycelial growth rate in the medium prepared with this formula was (1.51±0.03) mm/d. The yield of the first flush of mushrooms was (44.33±3.05) g, and the biological efficiency of the first flush was (44.00±3.46)%. The established mathematical model (R²>0.9) can accurately predict the effects of interactions among various factors on the mycelial growth rate and fruiting body yield.Conclusion The L. decastes strain exhibits broad adaptability to nutrient factors, and the established model can accurately predict the growth of this strain under different culture conditions.

Background Maize straw decomposition is slow during winter after incorporation, severely affecting winter wheat emergence and growth. Existing exogenous decomposition-promoting bacteria exhibit poor adaptability to local soils and limited decomposition efficacy.Objective To screen dominant bacterial strains with high cellulose-degrading capacity suitable for the Fluvo-aquic soil and Shajiang black soil environments, aiming to provide a theoretical basis and technical support for efficient straw utilization.Methods Soil samples were collected from long-term straw incorporation experimental fields. Cellulose-degrading bacteria were screened via dilution plating, hydrolysis zone, and enzyme activity assays. Isolates were identified through morphological observation, physiological-biochemical tests, and molecular biology methods. Enzyme production conditions were optimized via single-factor experiments. Functional gene annotation was performed based on whole-genome sequencing. Straw decomposition efficacy was validated in laboratory and field trials.Results An efficient cellulose-degrading strain, Bacillus subtilis K15, was isolated. Whole-genome sequencing revealed a single circular chromosome (approximately 4 082 766 bp, G+C content of 44.4%), with 4 309 genes predicted. Among these genes, 187 genes encoded enzymes of the carbohydrate-active enzyme (CAZy) family, including 60 glycoside hydrolases, which involved multiple enzymes related to cellulose degradation. The optimal enzyme production conditions were maltose of 30.0 g/L, beef extract of 30.0 g/L, pH 4.0, inoculum size of 2%, and incubation for 3 days, under which the carboxymethyl cellulase activity reached 76.9 U/mL. Field decomposition trials demonstrated that 60 days after inoculation of strain K15, the decomposition rates of maize straw in Shajiang black soil and Fluvo-aquic soil reached 48.9% and 37.4%, respectively, representing increases of 12.7% and 64.0% compared with the control.Conclusion K15 exhibits strong cellulose degradation capacity and significant decomposition-promoting effects. Its genome harbors abundant cellulose degradation-related genes. K15 significantly enhances straw decomposition efficiency in Shajiang black soil and Fluvo-aquic soil, demonstrating high application potential for promoting decomposition after straw incorporation.

Background Rice blast, caused by Magnaporthe oryzae, is one of the most devastating diseases in global rice production, causing serious yield losses and quality reduction.Objective To screen biocontrol strains effective against rice blast, characterize the plant growth-promoting and disease-suppressing effects of Bacillus altitudinis, and elucidate its antifungal mechanisms, thus providing a basis for practical application of this strain.Methods Antagonistic strains against rice blast were screened via the plate confrontation method. The selected strain was identified based on morphological, physiological, biochemical, and molecular characteristics. Pot experiments were conducted to evaluate its biocontrol efficacy and plant growth-promoting effects. The antifungal mechanism was preliminarily investigated by scanning electron microscopy (SEM) and LC-MS-based non-targeted metabolomics.Results A total of 69 endophytic strains were isolated from the rice roots in the ‘Huangkenuo’//‘Shanyou 63’ intercropping system. Strain YNDS1 was identified as B. altitudinis through morphological observation and phylogenetic analysis based on 16S rRNA and rpoB gene sequencing results, showing an inhibition rate of 63.30%. Pot experiments demonstrated that YNDS1 promoted the growth of ‘Lijiangxintuanheigu’ ‘Huangkenuo’, and ‘Hexi 39’, with the most pronounced growth-promoting effect on ‘Huangkenuo’. Biocontrol assays revealed that YNDS1 exhibited effective biocontrol effects against rice blast. Notably, in the susceptible variety ‘Lijiangxintuanheigu’, inoculation with YNDS1 either 24 h before or after pathogen inoculation significantly reduced the disease index, with the relative control efficacy of 68.75%. SEM observation revealed that YNDS1 induced abnormal swelling, entanglement, and adhesion in fungal hyphae. LC-MS-based non-targeted metabolomic profiling revealed that YNDS1 produced a variety of antifungal metabolites, including puromycin, streptozocin, dactimicin, surfactin, oxytetracycline, anisomycin, and surfactin B.Conclusion B. altitudinis YNDS1 exhibits strong biocontrol efficacy against rice blast and simultaneously promotes rice growth, demonstrating the potential as a promising biocontrol agent for rice blast management.

Background Plant endophytes, capable of producing metabolites identical or similar to their host plants in the long-term symbiosis, represent a vital resource for discovering novel antimicrobial agents.Objective This study aims to isolate endophytes from the bulbs of Lilium longiflorum, screen the strains with antimicrobial activity, and identify their potential active components.Methods Endophytes were isolated from the bulbs by a combination of the tissue separation and plate streaking methods. Strains exhibiting significant antimicrobial activity were screened through the plate confrontation assay and agar diffusion (well punch) method. The isolates were identified based on morphological characteristics and 16S rRNA gene sequences. Target strains were subjected to large-scale fermentation, and their metabolites were extracted with ethyl acetate. The antimicrobial spectra and minimum inhibitory concentrations (MICs) of the extracts were evaluated. Non-targeted metabolomics techniques were employed to identify metabolites and analyze the potential active components.Results Two endophytic bacterial strains (X66 and X95) were isolated from the bulbs of L. longiflorum. Both strains exhibited significant inhibitory activities against Staphylococcus aureus, Escherichia coli, and Aspergillus niger. They were identified as Bacillus velezensis. The ethyl acetate extracts of the two strains were evaluated for their antimicrobial spectra and MICs against 10 pathogenic microorganisms. The results demonstrated that the extracts inhibited the growth of other tested pathogens except Vibrio parahaemolyticus. Non-targeted metabolomics analysis identified a total of 6 553 metabolites from the ethyl acetate extracts of the two strains. Amino acids and their derivatives (19%) and benzenoids and their derivatives (17%) were the most abundant metabolites. The two strains shared 4 270 common metabolites. The top 30 most abundant common metabolites were primarily heterocyclic compounds, benzenoids and their derivatives, and amino acids and their metabolites. Metabolites such as glycine, leucine, benomyl, bufogenin, cinobufagin, morusin, and carvacrol were the key potential contributors to the antimicrobial activities of strains X66 and X95.Conclusion The endophytic strains X66 and X95 from L. longiflorum and their metabolites exhibit potent broad-spectrum antimicrobial activity. This study provides valuable microbial and chemical resources for the discovery of novel, efficient, and natural antimicrobial substances.

Background Fritillaria unibracteata Hisao et K. C. Hsia serves as the primary botanical origin of the precious Chinese medicinal material Fritillariae Cirrhosae Bulbus. Stem rot in F. unibracteata manifests as leaf yellowing, stem decay, and plant mortality, causing a substantial reduction in yield. This disease is often linked to stem pathogen infections, imbalances in soil rhizosphere microorganisms, and alterations in soil environmental factors. Nevertheless, the underlying mechanism of stem rot in F. unibracteata remains elusive.Objective We analyzed the disparities in the microbial community structures of rhizosphere soil and stem between diseased and healthy F. unibracteata plants, aiming to establish a theoretical basis for elucidating the causes of stem rot in F. unibracteata and formulating effective disease control strategies.Methods Illumina MiSeq was employed to sequence and analyze the community structure and diversity of bacteria and fungi in five types of samples: healthy rhizosphere soil (SFH), diseased rhizosphere soil (SFR), plant-free soil (SFW), diseased (LFD) and healthy (LFH) stems of F. unibracteata. Concurrently, the physicochemical properties of the rhizosphere soil of F. unibracteata under different health conditions were measured.Results The levels of soil pH, organic matter, available phosphorus, available potassium, total nitrogen, total potassium, and nitrate nitrogen in the stem rot group were higher than those in the healthy group and the control group (P<0.05). The alpha-diversity indices (Chao1, Observed_species, Pielou_e, and Shannon) of the rhizosphere soil samples were higher than those of the stem samples (P<0.05). The alpha-diversity indices in the LFD group were lower than those in the LFH group. The relative abundance of Monilinia in LFD and SFR groups were higher than those in LFH and SFH groups (P<0.05). Helotiales was a significantly different biomarker in the LFD group. The effect of available potassium on the bacterial and fungal community structures in the rhizosphere soil was most significant. The relative abundance of Monilinia was positively correlated with total nitrogen (P<0.05). Most of the nitrogen metabolism pathway functions in the LFD group were carried out by Monilinia.Conclusion Stem rot in F. unibracteata results in a decline in microbial diversity of both the rhizosphere soil and stems. Monilinia was a crucial factor in the development of stem rot in F. unibracteata.

Background Bovine enterovirus (BEV) is one of the important pathogens affecting the productivity of the cattle industry, and its prevalence has intensified with the expansion of modern livestock production. Although conventional detection methods such as qPCR are widely used, they often exhibit limitations such as false negatives or unstable results when dealing with samples containing low viral loads. Droplet digital PCR (ddPCR), with its high sensitivity and capability for absolute quantification, provides a more robust approach for detecting low-copy viral targets.Objective To establish a droplet digital PCR (RT-ddPCR) method for the detection of bovine enterovirus (BEV) with high specificity, sensitivity, and reproducibility.Methods Specific primers and probes were designed based on the conserved regions of the BEV genome. BEV cDNA was used as a template for PCR amplification, and the product was cloned into the pMD18-T vector to construct a plasmid standard. The annealing temperature of RT-ddPCR was optimized, and the specificity, sensitivity, and reproducibility of the established method were evaluated.Results The optimal annealing temperature for the detection method was 60 ℃. The established method showed high sensitivity, with a minimum limit of detection being 1.6 copies/μL. The method exhibited good reproducibility (coefficient of variation=8.6%). It showed strong specificity, with no cross-amplification of bovine viral diarrhea virus (BVDV), bovine kobuvirus (BKoV), bovine coronavirus (BCoV), or bovine parainfluenza virus type 5 (BPIV5). Parallel testing of 14 bovine fecal samples with RT-qPCR demonstrated superior detection performance of RT-ddPCR.Conclusion The established RT-ddPCR method for detecting BEV is highly specific, sensitive, and reproducible, and it is thus suitable for nucleic acid detection in clinical samples. It provides reliable technical support for the early diagnosis and accurate quantification of BEV infections.

Background Group A rotavirus (RVA) is one of the primary zoonotic pathogens responsible for diarrhea in infants, young children, and young animals, exhibiting strong infectivity.Objective To establish a rapid, specific method for the detection of RVAs of porcine, bovine, ovine, and human origins.Methods A pair of specific primers and one probe with TaqMan-MGB were designed based on the conserved sequence of the NSP5 gene of porcine, bovine, ovine, and human RVAs published in GenBank. A real-time fluorescent quantitative RT-PCR method capable of detecting porcine, bovine, ovine, and human RVAs was established after optimization of the annealing temperature (T_m) and primer and probe concentrations.Results The optimal T_m, primer concentration, and probe concentration of the established real-time fluorescent quantitative RT-PCR method were 51 ℃, 0.4 μmol/L, and 0.4 μmol/L, respectively. The method had high sensitivity, with the lowest limit of detection reaching up to 3.24 copies/μL. It had strong specificity, without cross-reactivity with other common porcine, bovine, and ovine pathogens. The method demonstrated good reproducibility, with the intra- and inter-group coefficients of variation being 0.063%-0.812% and 0.612%-1.016%, respectively. Moreover, the method showed excellent clinical applicability for the detection of porcine, bovine, ovine, and human samples.Conclusion A real-time fluorescent quantitative RT-PCR method was established in this study, providing technical support for the epidemiological investigation and early diagnosis of RVAs of porcine, bovine, ovine, and human origins.