[Objective] This study aims to investigate the soil fungal community structure in the tea plantations of Heshan and explore the relationship between fungal community and soil physicochemical properties. [Methods] We employed high-throughput sequencing to analyze the soil fungal community composition of 49 rhizosphere soil samples collected from healthy and mismanaging tea plantations in Heshan. The redundancy analysis (RDA) was performed to analyze the effects of soil physicochemical properties on the fungal community structure. The pairwise Wilcoxon signed-rank test was performed to compare the fungal taxa between the two kinds of tea plantations. FUNGuild was used to predict the soil fungal functions. [Results] Basidiomycota,Mortierellomycota, andAscomycota were the three dominant phyla in the rhizosphere soil of tea plantations in Heshan. The mismanagement of tea plantations increased the relative abundance ofBasidiomycota, but significantly decreased the relative abundance ofMortierellomycota. The fungal richness, Chao1 index, and ACE index were significantly lower in the mismanaging tea plantation than in the healthy tea plantation. The total nitrogen, total phosphorus, available phosphorus, organic matter, and available nitrogen were the primary driving factors for the differences of soil fungal β diversity. The soil pH, total phosphorus, exchangeable Ca²⁺ and Mg²⁺, available phosphorus, and available potassium were significantly correlated with the fungal taxa. Compared with the healthy tea plantation, the mismanaging tea plantation showed decreased relative abundance of core fungal taxa but increased relative abundance of medium and rare taxa. Ten of OTUs was common between healthy and mismanaging tea plantations. The pathogens causing tea gray blight, i.e.,Pseudopestalotiopsis theae andFusarium keratoplasticum, were identified in the healthy tea plantation. The relative abundance of biocontrol fungi,Trichoderma spirale andT.atroviride, significantly increased in the mismanaging tea plantation. The mismanaging tea plantation demonstrated increased relative abundance of pathotrophic, pathotrophic- saprotrophic-symbiotrophic, and symbiotrophic fungi but decreased relative abundance of saprotrophic-symbiotrophic fungi. [Conclusion] We elucidated the relationship of management mode with fungal community composition and soil physicochemical properties, providing the insights into the prevention and control of pathogens infecting black tea and the screening of biocontrol fungi in Heshan.

[Objective] To identify efficient aerobic denitrifying bacteria in the phyllosphere and provide new ideas for the prevention and control of air pollution by phytoremediation. [Methods] We used the enrichment culture method combined with the Griess reagent and bromothymol blue to isolate aerobic denitrifying bacteria from the phyllosphere and analyzed the phylogenetic relationship of the isolates based on the 16S rRNA gene sequences. Efficient aerobic denitrifying bacteria were screened out and their denitrification conditions were optimized. [Results] Thirteen strains were isolated from the phyllosphere of six landscape plant species:Photinia serratifolia,Ligustrumlucidum,Osmanthus fragrans,Camphora officinarum,Euonymus japonicus, andMagnoliagrandiflora. According to the 16S rRNA gene sequences, the 13 strains were classified into 7 genera, 7 families of 4 phyla. Specifically, 4, 3, and 2 strains belonged toEnterobacter,Achromobacter, andPseudomonas, respectively, and the remaining 4 strains belonged toAcinetobacter,Sphingobacterium,Microbacterium, andPseudarthrobacter. The comparative analysis revealed that strain SF outperformed the other strains in denitrification. The factors (carbon source, temperature, initial pH, C/N ratio, and rotational speed) influencing the denitrification performance of SF were optimized by single factor tests and response surface methodology. The denitrification conditions of SF were optimized as follows: glucose as the carbon source, initial pH 7.5. C/N ratio of 9.7, rotational at 180 r/min, and temperature of 33.5 ℃. Under the optimized conditions, the total nitrogen removal rate reached 93.3% in 72 h when the initial nitrate concentration was 361 mg/L. [Conclusion] The rich culturable aerobic denitrifying bacteria in the phyllosphere of landscape plants laid a foundation for phytoremediation. It is feasible to synergistically reduce nitrogen oxide pollution in the air by screening efficient denitrifying strains and improve the denitrifying performance by optimizing the culture conditions.

Adequate intake of probiotics helps in maintaining the homeostasis of the gut microbiota, which is of great significance for human intestinal health. However, probiotics are vulnerable to stress and necessitate stringent storage conditions in industrial settings, which pose challenges to the vitality maintenance of probiotics in transportation and shelf-life. Therefore, it is essential to develop the preparation process capable of protecting the high vitality of probiotics. Drying beneficial for sustaining probiotic vitality is often used to maintain the strain stability. Among the drying methods, freeze-drying is widely used. However, during the freeze-drying process, probiotics encounter environmental stress conditions, which lead to cellular damage and even death. Therefore, the freeze-drying protectants that can significantly improve probiotic survival rate have become a research hotspot in the industrial application of probiotics. This article systematically summarizes both the commonly used and the newly discovered protectants for freeze-drying of probiotics and elucidates their mechanisms of action. It provides an overview of the factors affecting cell viability post freeze-drying while outlining the prospective research directions of freeze-drying protectants. This review is expected to furnish theoretical substantiation for the development of freeze-dried probiotics with high vitality.

The roles of gut microbiota and its metabolites in the pathogenesis and rehabilitation of neurodegenerative diseases, gastrointestinal diseases, and musculoskeletal systemic diseases in the elderly are receiving increasing attention. Gut microbiota and its metabolites can regulate the functions of the cranial nervous system and the musculoskeletal system through various pathways, involving the immune, endocrine, and nervous systems. Conversely, the gut, brain, and musculoskeletal system can act on the intestinal system via inflammatory, metabolic, and mitochondrial pathways to regulate the gut microbiota. Accordingly, bidirectional signaling mechanisms are formedvia the gut-brain, gut-muscle, and gut-brain-muscle axes, which affect the organism health. This review summarizes that gut microbiota establishes gut-brain-muscle interconnections mainly through metabolites, intestinal permeability, and immune-neural pathways, providing new ideas for improving the brain neuroplasticity and muscle health.

[Background] Bacteria ofEnterobacteriaceae are the main pathogens of foodborne and clinical infections, posing a threat to human and animal health. The numerical identification method using API 20E as the "gold standard" is one of the main identification methods forEnterobacteriaceae. However, the existing numerical identification methods have problems such as laborious sample addition, low accuracy, and high prices. [Objective] To develop a semi-automatic, high-precision, and low-cost biochemical kit for identifying the bacteria ofEnterobacteriaceae based on the numerical identification method. [Methods] On the basis of the theoretical model and supporting software of the numerical identification system forEnterobacteriaceae established by our team, we designed and optimized 24 biochemical matrix trace formulations. Furthermore, a semi-automatic freeze-drying identification strip was developed. Using the commercialized numerical identification strip API 20E, MALDI-TOF MS, and 16S rRNA gene sequencing as the controls, we evaluated the performance of the developed biochemical kit that integrated semi-automatic biochemical identification strips and online analysis software. [Results] The biochemical spectra of 458 strains ofEnterobacteriaceae were obtained, with the overall identification accuracy of 98.5% at the genus level and 96.5% at the species level. The kit only needed twice sample addition to obtain the identification results, with the price only 4.46% that of API 20E. The shelf life of the product was 7 days, and the biochemical experiments had repeatability. [Conclusion] We develop a semi-automatic biochemical kit for identification ofEnterobacteriaceae based on the numerical identification method, which has simple operation, a low cost, and high accuracy. This study provides technical support for the identification ofEnterobacteriaceae and the development of biochemical products for numerical identification of other families and genera of bacteria.

[Objective] Prolidase is an enzyme that can hydrolyze proline or hydroxyproline residues from the C-terminal dipeptides (Xaa-Pro). A putative prolidase-encoding gene was identified in the genome ofPyrococcus yayanosii CH1 isolated from the deep sea. In this study, we characterized the enzymatic properties ofPyprol encoded byPYCH_07700in vitro, aiming to find a new prolidase. [Methods] Pyprol was heterologously expressed in the hyperthermophilic archaeonThermococcus kodakarensis TS559. The dipeptide Met-Pro was used as a substrate to test the prolidase activity of the purified recombinant protein. [Results] Pyprol showed the best performance at 100 ℃ and pH 6.0.Pyprol binding to Co²⁺ exhibited the maximum activity, and the optimal metal ion concentration was 1.2 mmol/L.Pyprol had catalytic activity in a wider pH range and can tolerate higher concentrations of metal ions than the prolidasePfprol fromP.furiosus.Pyprol was a piezotolerant protein with an optimal hydrostatic pressure of 40 MPa. It exhibited enhanced activities at 40, 70, and 100 ℃ under 40 MPa, compared with at the atmospheric pressure. [Conclusion] Pyprol is a novel thermostable and piezotolerant prolidase ofP.yayanosii CH1, which is an obligate piezophilic hyperthermophilic archaeon strain isolated from a deep-sea hydrothermal vent.

Listeria monocytogenes, a major zoonotic food-borne intracellular pathogen, is ubiquitous in the natural environment and easily contaminates animal-derived food products. The consumption of the contaminated food can cause severe listeriosis in both humans and animals, with the mortality rate reaching up to 30%. The antimicrobial therapy is the only feasible approach for treatingL.monocytogenes infection sinceL.monocytogenes is susceptible to multiple antimicrobials. However, the reports of multidrug-resistant strains are increasing due to the selective pressure exerted by the irrational use of antimicrobials or disinfectants. The antimicrobial resistance mechanisms ofL.monocytogenes are complex. Efflux pump proteins are crucial in bacteria and participate in various biological processes. Specifically, they can influence bacterial sensitivity to antibiotics, facilitate the efflux of toxic compounds, and affect bacterial virulence. Over the last two decades, scholars have conducted research on the efflux pumps-mediated resistance ofL.monocytogenes, identifying several efflux pump proteins associated with the efflux of antibiotics or toxic compounds. Additionally, some efflux pumps are involved in the virulence expression process ofL.monocytogenes. This paper reviews the research advances in the functions and regulatory mechanisms of efflux pumps in multidrug-resistantL.monocytogenes. It provides a theoretical foundation for probing into the environmental adaption mechanisms ofL.monocytogenes, curbing the spread of this pathogen, and identifying new drug targets for combating infections.

[Objective] To investigate the diversity of bacteria and fungi in the pathosphere ofPlasmopara viticola and screen out the strains with potential biocontrol effects on grape downy mildew. [Methods] The leaves infected byP.viticola were collected from seven representative grape-producing regions in northern and southern China in two consecutive years. The collected leaves were cultured in a humid environment, and the newly growing downy mildew was aseptically picked by forceps to prepare the sporangial suspensions ofP.viticola. The strains were isolated by the conventional culture method and identified based on the morphological characteristics, BOX-PCR fingerprints, and molecular sequences. Furthermore, the clustering analysis of different strains was conducted. Sporangial inhibition was tested with equal volumes of strain suspension or fermentation mixed with the sporangial suspension ofP.viticola, and the control effects of isolates and their sterile fermentation against grape downy mildew were tested on detached grape leaves. [Results] A total of 90 bacterial strains and 110 fungal strains were isolated, belonging to eight bacterial genera and 14 fungal genera, respectively. The pathosphere ofP.viticola in the same province and the same year exhibited similar microbial community composition. Notably, strains ofPseudomonas spp. andCladosporium spp. exhibited stable populations on grape cultivars collected from different provinces. A majority (over 80.0%) of strains with stable populations in two consecutive years demonstrated significant biocontrol effects against grape downy mildew. SixAcremonium strains with ubiquitous distribution demonstrated the biocontrol effect up to 100.0%. Sterile fermentation of the fungal strainsAspergillus niger NX2F,Thecaphora amaranthi BJ1G, andRhizopus stolonifer BM1L showed the control effects of 100.0% against grape downy mildew. [Conclusion] The culturable bacterial and fungal communities in the pathosphere ofP.viticola were mainly affected by geographical factors in different provinces, and most of the culturable microorganisms presented stable and strong biocontrol effects on grape downy mildew. To the best of our knowledge, it is the first comprehensive report thatAcremonium spp. were epibiotic fungi and consistently associated withP.viticola, providing rich and valuable biocontrol resources for grape downy mildew.

[Objective] Fusarium proliferatum is one of the major pathogens causing root rot of alfalfa. This study aims to investigate the function of the aconitase family inF.proliferatum and give insights into the molecular mechanisms underlying the physiological metabolism of this pathogen. [Methods] We employed the hmmsearch tool to identify the proteins containing the aconitase domain inF.proliferatum and then carried out the phylogenetic analysis. real-time PCR and SWISS-MODEL were employed to analyze the expression profiles ofFpACO genes and the protein structures, respectively. The homologous recombination method was used to construct theFpACO-deleted mutants ofF.proliferatum. Furthermore, we explored the growth, sporulation, spore morphology, stress responses, and pathogenicity of ΔFpACO3, ΔFpACO4-1, and ΔFpACO4-2 and measured the mitochondrial metabolism indicators of the mutants. [Results] FpACO4-1 and FpACO4-2 were involved in sporulation and spore morphogenesis. FpACO3, FpACO4-1, and FpACO4-2 were responsible for regulating the sensitivity ofF.proliferatum to cell wall stress and metal ion stress. Moreover, FpACO3, FpACO4-1, and FpACO4-2 affected the mitochondrial metabolism indicators, including the total aconitase activity, the ATP level, the hydrogen peroxide level, and the expression of key genes in the tricarboxylic acid cycle. [Conclusion] The aconitase family members are involved in the regulation of the processes such as sporulation, spore morphogenesis, response to cell wall stress and metal ion stress, and mitochondrial metabolism inF.proliferatum.

[Objective] To study the spatial and temporal distribution characteristics, community structure, and diversity of uncultured myxobacteria in the rhizosphere soil ofPhragmitesaustralis in the Ebinur Lake wetland, so as to enrich the knowledge of myxobacteria resources in saline-alkaline wetlands, lay a foundation for exploiting the myxobacteria resources in extreme environments, and provide data support for the restoration of saline desert ecosystems. [Methods] The rhizosphere soil samples ofP.australis were collected from 10 sites in Ebinur Lake wetland in 3 months, and high-throughput sequencing was conducted for the V4–V5 region of the 16S rRNA gene to reveal the diversity and spatial and temporal distribution of myxobacteria. [Results] The abundance of myxobacteria, as indicated by the presence of 16S rRNA gene tags, ranged from 0.22% to 3.54% of the total bacteria in the Ebinur Lake wetland. The highest diversity was observed in July and at the sampling site 4, suggesting the correlations of genus diversity with both seasons and sample sites. A total of 14 genera of myxobacteria belonging to 8 families of 3 suborders were identified. Among them,Haliangium was the dominant genus, with the relative abundance of 10.83%–71.01%. Network co-occurrence diagrams showed that most of the bacteria interacted with myxobacteria. Spearman correlation analyses showed that the Shannon, Chao1, and ACE indices of bacteria influenced the diversity and richness of myxobacteria. The redundancy analysis (RDA) showed that soil inorganic nitrogen (IN), organic matter (OM), and water-soluble magnesium ions (Mg²⁺) were the main abiotic factors influencing the diversity and community structure of myxobacteria. [Conclusion] The Ebinur Lake wetland is rich in myxobacteria, the diversity and community structure of which present spatial and temporal variations. Biotic factors (bacteria) and abiotic factors (soil physico-chemical properties) jointly affect the diversity of myxobacteria.