Abstract:Saprolegniasis caused by the pathogenic fungi of Saprolegnia spp. is widely prevalent worldwide. The prohibition of the effective and specific drug malachite green for the prevention and control of Saprolegnia, as well as the non-specific hosts and drug resistance development via biofilm formation of Saprolegnia, increases the difficulty in the prevention and control of this disease, which seriously affects the healthy development of freshwater aquaculture. This paper reviewed the reproductive patterns, identification methods, and prevention and control measures of Saprolegnia. With the mechanism of drug resistance of other related pathogens in aquaculture as a reference, we proposed the measures including improving the identification methods of Saprolegnia, enriching the species of Saprolegnia in the culture collection, elucidating the mechanism of Saprolegnia in developing drug resistance via biofilm formation, establishing the disease models of Saprolegnia infection, developing efficient compound Chinese herbal medicines, optimizing the extraction process of antifungal compounds from Chinese herbal medicines, and evaluating the effectiveness and safety of antifungal compounds for the comprehensive prevention and control of Saprolegnia. The review provided ideas for the development of effective agents for the prevention and control of saprolegniasis in fish.

Abstract:Marine hydrothermal systems are high-temperature extreme environments formed under the influence of geothermal activities. According to early studies, γ-Proteobacteria were the main members of sulfur-oxidizing chemolithoautotrophic bacteria in deep-sea hydrothermal vents. At the end of the last century, molecular ecological studies revealed that Campylobacteria (former ε-Proteobacteria) were the dominant bacteria in hydrothermal habitats, such as hydrothermal solution, smoker body, megafauna, and underground sediments, with ecological significance in the life processes including sulfur oxidation and hydrogen oxidation in hydrothermal areas. The article comprehensively reviews the research progress of Campylobacteria in hydrothermal vents from ecological, physiological, and other perspectives. It extensively describes the ecological distribution, diverse metabolic types, strain characteristics, and taxonomic status of Campylobacteria, showcasing the utilization mechanisms of Campylobacteria for elements such as carbon, nitrogen, sulfur, and hydrogen.

Abstract:Staphylococcus aureus secretes a variety of toxins in the course of infection, and the toxins damaging the host cell membrane have garnered great attention. Natural medicines are characterized by structural diversity and low toxicity, and thus it has great potential to mine lead compounds from plants, animals, and microorganisms. This paper reviews the properties, structural characteristics, and mechanism of membrane-damaging toxins and summarizes the natural medicines against these toxins, providing a basis for the selection of new drugs and the development of anti-toxin therapies in the future.

Abstract:Fluoride has been used as an effective anti-caries agent for decades. Fluorinion can inhibit the activities of key enzymes in microbial metabolism or change the permeability of cell membrane, thus inhibiting the growth of major cariogenic bacteria such as Streptococcus mutans. Moreover, it can change the oral microbiome structure of caries patients. However, the long-term excessive use of fluoride may lead to the emergence of fluoride-resistant strains and reduce the anti-caries effect of fluoride. The development of sequencing technology enables researchers to gain deep understanding of fluoride resistance mechanism in oral microorganisms and the influence of fluoride on oral microecology. In recent years, the combination of fluorine and new biomedical materials provides a new strategy for controlling fluorine-resistant strains. This paper reviews the latest studies about the effects of fluoride on oral microecology, including the generation and mechanism of fluoride resistance in oral microorganisms, the effects of fluoride on human oral microbiome, and the combined use of fluorine and new biomedical materials, aiming to provide a theoretical basis for the further research and application of fluoride in oral health.

Abstract:Edible fungi with rich nutrients and unique flavors are popular among consumers. The flavor of edible fungi is mainly composed of non-volatile taste components and volatile odor components, which affect the quality and consumer acceptance of edible fungi. Odor is perceived through the olfactory system and can promote digestion and absorption by increasing people’s pleasure and stimulating appetite. This paper comprehensively summarizes the volatile odor components in edible fungi, mainly including sulfur-containing compounds, eight carbon compounds, and other compounds. Subsequently, the development of separation techniques for these components such as steam distillation (SD), simultaneous distillation extraction (SDE), supercritical fluid extraction (SFE) and solid phase micro-extraction (SPME) were summarized, as well as identification techniques such as gas chromatography-mass spectrum (GC-MS) and gas chromatography-ion migration spectrum (GC-IMS), and the advantages and disadvantages of these techniques were generalized. The purpose of this paper is to provide a reference for the future research on volatile odor components in edible fungi and the development of flavor products from edible fungi.

Abstract:Second messengers play important roles in the physiological activities of bacteria. 3',5'-cyclic adenosine monophosphate (cAMP) as a second messenger exists ubiquitously in bacteria. Under normal physiological conditions, the synthesis and metabolism of cAMP in bacterial cells are in dynamic balance, and cAMP functions as a transcription regulator by forming complexes with its receptor protein Crp. This article reviews the regulatory mechanisms of cAMP-Crp in lethal stress response, bacterial population competition, and biofilm formation, as well as the pathways through which cAMP affects the virulence of different pathogens. It calls for researchers to pay attention to the upstream pathways of bacterial cAMP in response to host or external environmental changes. Comprehensively understanding the cAMP-mediated bacterial stress responses and virulence regulation may contribute to the prevention and treatment of bacterial infections.

Abstract:Histidine kinases are a crucial class of protein kinases involved in signal transduction pathways, playing a key role in bacterial responses to environmental stress. After more than 60 years of research, researchers have identified histidine kinases in a variety of bacteria. Bacterial histidine kinases are classified into 11 families, each encompassing multiple types. They accomplish the signal transduction process through one-step phosphorylation or multi-step cascading phosphorylation, thus regulating the expression of genes associated with stress responses and forming complex and diverse signal perception systems. This enables bacteria to effectively respond to temperature changes, adapt to antibiotic pressure, produce virulence, acclimate to acidic environments, and resistance to organic compounds. This review provides insights into the roles and mechanisms of histidine kinases, bacterial survival strategies and adaptability and facilitating the research on the application of histidine kinases in biology, medicine, and detection of small molecules.

Abstract:[Background] 1,2,4-butanetriol (BT), a chiral polyol, plays a role as a platform chemical in the synthesis of energetic materials such as 1,2,4-butanetriol trinitrate, which is used as a propellant in a variety of military applications, including aircraft, rockets, and missiles. With the rapid development of synthetic biology, building microbial cell factories for the production of 1,2,4-butanetriol has received increasing attention. [Objective] In this study, we employed metabolic engineering to optimize the exogenous 1,2,4-butanetriol synthesis pathway in a pre-constructed strain of Candida tropicalis, aiming to reduce the accumulation of intermediates and increase the production of 1,2,4-butanetriol. Furthermore, we evaluated the ability of the engineered strain to produce 1,2,4-butanetriol by fermentation with inexpensive corncob hydrolysate. [Methods] We employed promoter engineering to optimize the expression level of the xylose dehydrogenase gene and reduce the accumulation of xylonate. Furthermore, we enhanced the production of 1,2,4-butanetriol in C. tropicalis by using calcium carbonate as a neutralizer to regulate the pH and optimizing the concentration of iron ions in the fermentation medium. [Results] Through the combined efforts of metabolic engineering and fermentation process optimization, the final yield was increased by 42%, reaching 6.20 g/L in a 5 L fermenter. In addition, the engineered strain was capable of producing 2.60 g/L 1,2,4-butanetriol by using corncob hydrolysate as the substrate. [Conclusion] We improve the ability of C. tropicalis to synthesize 1,2,4-butanetriol by metabolic engineering and fermentation process optimization. Moreover, we for the first time evaluate the feasibility of C. tropicalis cell factories for the synthesis of 1,2,4-butanetriol with corncob hydrolysate, which provides support the large-scale production of 1,2,4-butanetriol by fermentation with biomass feedstocks.

Abstract:[Background] The Manghe River, a downstream tributary of the Yellow River, suffers from heavy metal-containing wastewater discharge over a long period of time, and its sediments are characterized by the presence of heavy metal composite pollution dominated by chromium contamination, with the formation of a unique microbial community in the contaminated area. [Objective] To screen the fungi capable of tolerating and transforming high concentrations of Cr(VI) in the sediments of the contaminated area and explore the Cr(VI) transformation ability and mechanism. [Methods] The fungi capable of tolerating and transforming high concentrations of Cr(VI) were screened by the gradient culture method and identified by morphological observation and ITS sequencing. The mechanism of Cr(VI) transformation by the strains was investigated based on the reduction ability of different components of the strains, scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). [Results] Two fungal strains p18 and p20 tolerant to 1 000 mg/L Cr(VI) were isolated and identified as Trichoderma yunnanense and Fusarium annulatum, respectively. The two strains showed the Cr(VI) removal rates of 79.40% and 63.48% and the Cr(VI) reduction rates of 73.55% and 50.94%, respectively, after being cultured with 100 mg/L Cr(VI) for 120 h. In the medium with 500 mg/L Cr(VI), p18 and p20 accumulated the highest amounts of Cr per gram of dry mycelia, which reached 10.84 mg and 6.98 mg, respectively. SEM revealed that the surfaces of p18 and p20 cells were adorned with Cr particles after exposure to Cr treatment. FTIR indicated that -NH, -OH, C=O, C-H, and -CONH₂ were involved in the adsorption of Cr. XPS and XRD confirmed that the strains transformed Cr(VI) into Cr(OH)₃, which existed in an intermediate state between amorphous and crystalline forms. The predominant substances responsible for Cr(VI) reduction were the extracellular secretion of the two strains. [Conclusion] The two highly Cr(VI)-tolerant fungal strains, T. yunnanense and F. annulatum, demonstrate efficient transformation of Cr(VI), which provide a basis for the heavy metal transformation and remediation of the river suffering from long-term contamination.

Abstract:[Background] The bacterial and microeukaryotic communities in activated sludge (AS) play crucial roles in wastewater treatment. However, limited information is available regarding the microbial generalists and specialists in AS. [Objective] Aims to study the relationships between environmental factors and AS microbial generalists and specialists, and explore the community assembly mechanisms, evolutionary rates, and diversification potential of AS microbial generalists and specialists. [Methods] Amplicon sequencing and multivariate statistical analysis were employed to explore the community structures of AS microbial generalists and specialists from wastewater treatment plants located in the southeastern coastal region of China. Additionally, the infer community assembly mechanisms by phylogenetic-bin-based null model analysis (iCAMP) was conducted to explore the assembly mechanisms of those groups, while the evolutionary rates were assessed by the binary-state speciation and extinction (BiSSE) model. [Results] The community structures of bacterial generalists and specialists were significantly correlated with electrical conductivity, ammonia nitrogen, and nitrite nitrogen, while the total nitrogen was the primary factor influencing the community structures of the microeukaryotic generalists and specialists. However, electrical conductivity and nitrite nitrogen played major roles in shaping the microeukaryotic specialists. Stochastic processes played a dominant role in the community assembly of both bacteria and microeukaryotes in AS, especially for the generalists than the specialists as well as for the microeukaryotes than the bacteria. Bacteria exhibited higher speciation rates and lower extinction rates than microeukaryotes, which suggested higher diversification potential. The specialists exhibited higher speciation rates, extinction rates, and diversification potential than the generalists. [Conclusion] Ammonia nitrogen, nitrite nitrogen, and electrical conductivity were significant environmental factors influencing the community structures of bacterial generalists and specialists, and microeukaryotic specialists. Stochastic processes mainly drove the community assembly of the generalists and specialists. Moreover, the AS generalists and specialists exhibited different speciation rates.

Abstract:[Background] Zabuye Salt Lake with high concentrations of CO₃^2-, HCO₃^-, and Na⁺ may harbor Halomonas strains with potential applications. [Objective] To screen the Halomonas strains capable of accumulating the compatible solute ectoine, analyze the factors influencing ectoine accumulation, and optimize the fermentation conditions for ectoine accumulation in these strains. [Methods] The Horikoshi-I medium was used to isolate the strains with salinity tolerance and capable of efficiently accumulating ectoine from the water samples collected from Zabuye Salt Lake. The strains were then characterized in terms of biochemical properties and taxonomic status. Single factor tests, Plackett-Burman design, Box-Behnken design, and HPLC were employed to analyze the key factors influencing the intracellular ectoine accumulation and optimize the fermentation conditions. [Results] A total of 10 strains belonging to 5 species of Halomonas were isolated from Zabuye Salt Lake, and the dominant species was H. alkaliphila (4 strains, 40%). H. alkaliphila ZB109 presented good growth within the salt range of 0.5-2.5 mol/L and pH 8.0-10.0, with the initial ectoine accumulation of 303.62 mg/L. The colonies of ZB109 were round, yellow, with smooth edge. ZB109 was a Gram-negative bacterial strain with short rod cells growing cilia around. NaCl, Mg²⁺, and the concentration of sodium l-glutamate (substrate) were the key factors influencing the accumulation of ectoine by strain ZB109. After the fermentation conditions were optimized by response surface methodology, strain ZB109 was able to accumulate ectoine up to 696.313 mg/L (48 h) in a single batch of shake flask fermentation. [Conclusion] Strain ZB109 with both salt and alkali tolerance demonstrates stronger potential in the accumulation of ectoine than other wild-type strains of Halomonas. It serves as an elite strain for the large-scale production of ectoine by fermentation.

Abstract:[Background] Leptospirillum ferrodiazotrophum can produce a large amount of secondary minerals during the culture. [Objective] This study optimized the culture conditions of L. ferrodiazotrophum for secondary mineral production, aiming to provide materials for the subsequent application of biogenic secondary minerals. [Methods] Single factor tests were carried out to investigate the effects of pH, temperature, rotation speed and liquid loading on the production of secondary minerals by L. ferrodiazotrophum, on the basis of which the response surface method was employed to optimize the culture conditions. Subsequently, the produced secondary minerals were characterized and tested. [Results] The single factor tests showed that the secondary mineral yield reached the highest under the conditions of pH 3.00, 35.0 ℃, and rotation speed of 150 r/min, and the effect of liquid loading on the secondary mineral production was insignificant. The optimal conditions for producing secondary minerals were pH 2.82, 31.7 ℃, and rotation speed of 135 r/min. After the optimization, the yield increased from the highest value of 57.714 mg/(L·h) in the single factor tests to 65.436 mg/(L·h). X-ray diffraction results showed that the produced mineral had poor crystallinity and was an amorphous hydroxyl high-iron mineral. The mineral had a short needle-like structure and a large specific surface area. [Conclusion] This study optimized the biosynthesis conditions of secondary minerals through single factor tests and response surface design, laying a foundation for applying secondary minerals in the future.

Abstract:[Background] Desert soil is barren and saline-alkaline, in which the rhizosphere microorganisms can help the host plants to tolerate stress, which is of great significance for maintaining the ecosystem function. [Objective] To evaluate the growth-promoting properties and germination-promoting effects of rhizosphere and nonrhizosphere bacteria of Ammodendron bifolium, and obtain elite bacterial resources with growth-promoting effects and stress tolerance. [Methods] We employed the plate culture method to examine the nitrogen-fixing, phosphorus-solubilizing, siderophore-secreting, and hydrolase-producing properties of the strains. The abilities of the strains to solubilize phosphorus and produce hydrolase and indole-3-acetic acid (IAA) were quantitatively measured by the colorimetric method. The germination-promoting effects of the strains were tested by strain-seed co-cultivation, and the tolerance of the strains to drought and saline-alkali stress was observed. [Results] Thirty-five strains showed nitrogen-fixing activity, mainly belonging to Proteobacteria in the rhizosphere and Firmicutes in the nonrhizosphere. Strains Ba-12, Ra-2, Rb-12, and Rb-18 had the abilities to solubilize inorganic and organic phosphorus, mainly originating from the rhizosphere. One strain (Rb-12) was capable of secreting siderophores, originating from the rhizosphere. Six strains had the ability of producing IAA, of which strains Rb-5 and Rb-12 with the highest levels of IAA came from the rhizosphere. Eight strains were capable of producing amylase, protease, and cellulase simultaneously, coming from the nonrhizosphere. The 10 strains producing two enzymes and the 13 strains producing one enzyme mainly came from the rhizosphere. One strain, i.e, Bc-5, showed a significant germination-promoting effect, originating from the nonrhizosphere. Most of the tested strains tolerated 30% PEG6000, 2%-4% NaCl, and pH 11.5, and the strain with the strongest stress tolerance came from the rhizosphere. [Conclusion] Strains Ba-12, Ra-2, Rb-5, Rb-12, and Rb-18 with excellent growth-promoting properties mainly originate from the rhizosphere, which indicates the significant rhizosphere effect of A. bifolium. However, the germination-promoting effect of the nonrhizosphere strain Bc-5 is not related to the growth-promoting properties, which requires further exploration.

Abstract:[Background] The mechanism of community assembly is a hot topic in microbial ecology, and it remains uncertain whether the conclusions are completely applicable on a local scale. [Objective] To verify the community assembly mechanism on a small local scale and evaluate the applicability of relevant theories. [Methods] We compared the composition and assembly mechanisms of soil fungal communities in the forest, shrub, and grassland ecosystems in Lüliang, Shanxi. [Results] The results of high-throughput sequencing and statistical analysis indicated that the soil fungal communities presented different biogeographic distribution patterns in different ecosystems. The Sobs, ACE, and Chao1 indices of soil fungi in the forest ecosystem were 699.50, 835.22, and 838.36, respectively, which were higher than those of the other two ecosystems (P<0.05). The network analysis and Zi-Pi values showed that the network modules had regional differences, and the number and composition of keystone species were different among different ecosystems. According to the regression results, neutral community model analysis results, |βNTI|<2, RCbray values, the community migration rates are 0.003, 0.001 and 0.001, and a significant distance-delay distribution pattern (R=-0.059, P=0.018), we hypothesized that stochastic processes dominated the assembly of fungal communities in this study area. [Conclusion] The keystone species (Geopora, Trichoderma, etc.) are involved in the symbiotic network formation and community assembly and demonstrate broader functions and stronger adaptability to different ecosystems than the dominant species (Metarhizium, Gibberella, etc.). On this local scale, both deterministic and stochastic processes drive community assembly, with the former being dominant. This study aims to provide a scientific basis for the protection of different ecosystems in Lüliang of the Yellow River basin and enrich the clues for the universal application of theories in macroecology.

Abstract:[Background] Iron is a microelement essential for the growth and metabolism of microorganisms, playing a role in vital physiological activities like respiration, DNA precursor synthesis, gene regulation, and response to oxidative stress. Studies have confirmed the tolerance of Streptomyces flavus TRM45540, an actinomycete strain isolated from Lop Nur in Xinjiang, to ferric ions. It is of great significance to elucidate the response mechanism of S. flavus TRM45540 to iron stress. [Objective] To reveal the iron tolerance mechanism of S. flavus TRM45540. [Methods] S. flavus TRM45540 was cultured in the ISP4 liquid media supplemented with different levels of ferrous sulfate. Transcriptome sequencing was employed to explore the response mechanism to iron. Additionally, scanning electron microscopy and energy spectrum analysis were employed to observe changes in mycelial surface morphology as well as elemental species and content under ferric ion stress. [Results] The supplementation of ferrous sulfate at low (1-500 mg/L) and high (2 500-4 500 mg/L) levels had negative effects on the growth of S. flavus TRM45540. However, supplementing ferrous sulfate at 500-2 500 mg/L promoted the biomass accumulation of S. flavus TRM45540. With the increase in the supplementing level of ferrous sulfate, a large amount of extracellular polymers substances (EPSs) were generated outside the mycelia of S. flavus TRM45540. The energy spectrum analysis showed increases in the oxygen and iron content and a decrease in the nitrogen content of EPS, suggesting a polysaccharide composition. The transcriptome analysis showed that differentially expressed genes post ferric ion stress were associated with multiple metabolic pathways including the ABC transporter system, two component system, ferric ion transport, amino acid metabolism, glutathione expression, and porphyrin metabolism. [Conclusion] The ferric ion stress induced the secretion and export of biomolecules to the cell surface of S. flavus TRM45540, leading to the formation of polysaccharide-based EPS. The EPS was complexed with a large amount of ferric ions on the bacterial cell surface, thereby impeding the influx of ferric ions. Additionally, the activation of the two component system triggered a cascade of responses to ferric ion stress. This included upregulation of acidic amino acids, enhanced synthesis of porphyrins binding to ferric ions, and increased biosynthesis of cysteine and glutathione involved in ferric ion removal. These pathways coordinated to reduce the cellular damage caused by high ferric ion levels.

Abstract:[Background] Alkaline phosphatase (ALP) with the ability of degrading endotoxin (lipopolysaccharide, LPS) can prevent and weaken intestinal inflammation. Different strains of Bacillus subtilis can secrete ALP with different activities, which may be an important factor in the health effects of B. subtilis. [Objective] To study the enzymatic properties and endotoxin-degrading performance of the recombinant protein by cloning the ALP gene phoA from a B. subtilis strain with high ALP activity and expressing this gene in Escherichia coli. [Methods] We used the organophosphorus agar medium to isolate B. subtilis strains from the soil samples with rich organic matter. The ALP activity was assayed with 4-nitrophenyl phosphate disodium salt hexahydrate (p-NPP) as the substrate. The strains producing ALP with high activity were screened and phoA was cloned and expressed. The enzymatic characteristics of recombinant PhoA were studied, and the LPS-attenuating effect of PhoA was evaluated in mice. [Results] Fourteen strains of B. subtilis with high ALP activities were screened out, and phoA was cloned from the strain 35-16-1 with the highest ALP activity and expressed solubly in E. coli BL21(DE3). The enzymatic properties of PhoA after purification were studied. PhoA showcased the optimum reaction performance at 70 ℃ and pH 9.8. Mg²⁺ activated the activity of PhoA, with the maximum activating effect at 14 mmol/L. Ca²⁺ inhibited the activity of PhoA. K⁺, Zn²⁺, Mn²⁺, and Fe²⁺ had no significant effect on PhoA activity. With p-NPP as the substrate, PhoA presented the V_max of 179.86 mmol/(L·min), K_m of 2.38 mmol/L, and k_cat of 246.83 s^‒1 at 37 ℃. The specific activity of 6 550.00 U/mg under optimal conditions. The toxicity of LPS treated with recombinant PhoA was significantly reduced in mice. [Conclusion] The phoA gene of B. subtilis 35-16-1 can be expressed with high ALP activity in E. coli and the recombinant protein can degrade endotoxin.

Abstract:[Background] Aspergillus niger is a commonly used filamentous fungal chassis, whereas the genetic manipulation of large DNA fragments of this fungus lacks tools and is inefficient. The massive genomic data include a large number of unidentified gene clusters for the synthesis of secondary metabolites, which are difficult to be cloned due to the large molecular weights. In addition, the relationships between most genes and products have not been resolved. [Objective] To develop a method for direct cloning of large DNA fragments for A. niger and achieve the heterologous production of kojic acid in A. niger by cloning and expressing the gene cluster (about 30 kb) for the biosynthesis of kojic acid from Aspergillus oryzae. [Methods] Transformation-associated recombination (TAR) cloning was employed to construct the TAR capture backbone vector pSEA-TAR for the transformation of A. niger. The homologous DNA sequences (about 1 kb) flanking the gene cluster for the biosynthesis of kojic acid were successively introduced into pSEA-TAR and separated by a unique digestion sequence of Xho Ⅰ. The obtained capture vector pSEA-KLR for the gene cluster was linearized by Xho Ⅰ and transformed into Saccharomyces cerevisiae VL6-48 together with the Not Ⅰ/Sbf Ⅰ digested A. oryzae genome containing the complete gene cluster as well as the flanking homologous sequences. The recombinants successfully capturing the gene cluster for the biosynthesis of kojic acid were screened by the medium lacking corresponding nutrients. The plasmid was extracted from the recombinant and electroporated into Escherichia coli for amplification. The Agrobacterium tumefaciens-mediated method was used for transformation of A. niger. The obtained transformants carrying the gene cluster for kojic acid biosynthesis were subjected to fermentation, and the kojic acid titer was measured. [Results] A large DNA fragment capture vector pSEA-TAR was obtained based on TAR cloning and adapted to the expression of A. niger with ARSH4/CEN6, TRP1, hph, and LB/RB-T-DNA repeats. pSEA-TAR-KA was obtained as a recombinant plasmid containing a gene cluster for the biosynthesis of kojic acid by an efficient homologous recombination system of S. cerevisiae, demonstrating a capture success rate of 5.9%. All the 10 A. niger recombinant strains (KA1-KA10) carrying the gene cluster produced kojic acid in fermentation, with the highest kojic acid titer (5.86 g/L) obtained by fermentation with the strain KA-2 for 7 d. [Conclusion] A TAR cloning system was constructed and adapted to A. niger for the efficient capture, recombination, and expression of large biosynthetic gene clusters. The performance of the system was verified by the capture of A. oryzae-derived gene cluster for the biosynthesis of kojic acid and the successful synthesis of kojic acid by A. niger. This study enriched the role of A. niger as a chassis in the green biomanufacturing of important compounds.

Abstract:[Background] The long-term flooding conditions in paddy fields and root exudates of rice plants create a favorable environment for nitrogen-fixing microorganisms, among which nitrogen-fixing cyanobacteria are the main contributors to biological nitrogen fixation in paddy ecosystems. [Objective] To obtain efficient nitrogen-fixing cyanobacterial strains and provide strain resources for enhancing biological nitrogen fixation in paddy fields. [Methods] The BG-11₀ nitrogen-free medium was used to isolate nitrogen-fixing cyanobacteria from different paddy soil samples. The isolates were screened based on nitrogenase activity, indole-3-acetic acid (IAA) secretion ability, and siderophore production ability. The selected efficient nitrogen-fixing strain was identified by morphological observation and methods of molecular biology. The plant growth-promoting effect of the selected strain was evaluated by hydroponic and pot experiments. [Results] An efficient nitrogen-fixing [239.27 nmol/(min·mg)] strain with high IAA production (7.70 μg/mL) and robust siderophore secretion ability was screened out. It was identified as a strain belonging to Aliinostoc of Nostocaceae and named Aliinostoc sp. d389-10. This strain significantly promoted the growth of rice seedlings in hydroponic experiments, increasing the plant height, root length, and dry weight by 22.42%, 54.76%, and 57.80%, respectively. In pot experiments, inoculation with d389-10 significantly improved soil nitrogenase activity and rice yield, while significantly increasing soil organic carbon, total nitrogen, and available nutrients. [Conclusion] The strain d389-10 screened out is an efficient nitrogen-fixing cyanobacterial strain with rice growth-promoting effect, with research value and application potential.

Abstract:[Background] Plant endophytes represent the treasure for investigating microbial diversity and adaptive evolution. Cistanche is a genus of medicinal plants belonging to Orobanchaceae and honored as “ginseng of the deserts”. However, few studies have been carried out on the endophytes of Cistanche. [Objective] To investigate the diversity of endophytic bacteria in different Cistanche species and explore the endophytic bacterial resources. [Methods] The plants of Cistanche tubulosa (Schrenk) R. Wight (GH) and C. deserticola Y.C. Ma (HM) were sampled and subjected to high-throughput sequencing. The conventional microbial isolation method was used to isolate endophytic bacteria, and the isolates were identified by 16S rRNA gene sequence alignments. Subsequently, the stress tolerance, plant growth-promoting effects, and antimicrobial activities of the strains were evaluated. [Results] The high-throughput sequencing revealed a total of 1 086 OTUs of endophytic bacteria in GH and HM samples, among which 46 (4.24%) common OTUs were shared by the two species. The OTUs belonged to 226 genera, 104 orders of 19 phyla and some uncategorized bacteria. Proteobacteria was the dominant phylum in both samples, accounting for 69.46%. Significant differences were observed in the community structure of endophytic bacteria between the two species. In addition, 65 strains of endophytic bacteria were isolated from the plants, belonging to 34 species, 20 genera of 3 phyla (Bacillota, Proteobacteria, and Actinomycetota), and Bacillota had the highest relative abundance. Furthermore, the stress tolerance, plant growth-promoting effects, and antimicrobial activities of the isolates were evaluated. [Conclusion] The community structure of endophytic bacteria presented significant differences between Cistanche species. This study isolated several endophytic bacterial strains, which provided a basis for subsequent applications.

Abstract:[Background] Cordyceps militaris is a medicinal fungus with high nutritional and medicinal values, and its fruiting bodies are mainly produced by solid-state fermentation. [Objective] To provide a new option for the production of C. militaris fruiting bodies by liquid fermentation and determine the nutrient composition and pigment stability of the fruiting bodies produced. [Methods] Shaking culture was employed for the extensive mycelial growth of C. militaris in a liquid medium, and then static culture with illumination was carried out for inducing fruiting body formation and growth. The nutrient composition of the fruiting bodies was determined by chemical assays, and the absorbance changes of pigments extracted from the fruiting bodies were determined to evaluate the pigment stability. [Results] The cultivation of C. militaris by liquid fermentation took 10.8 d for primordium emergence and 37.3 d for fruiting body growth (from primordium emergence to fruiting body harvest). The production cycle in this cultivation mode was 48.1 d, 9.7 d less than that (57.8 d) of solid-state fermentation (control). The fresh fruit body yield was 6.72 g per bottle, lower than that (8.29 g per bottle) of the control. The content of crude protein, crude fat, and ash was 44.5%, 2.6%, and 8.8%, respectively, in the fruiting bodies cultivated from liquid fermentation and 28.5%, 1.4%, and 4.6%, respectively, in the control, with increases of 56.14%, 85.71%, and 91.30%, respectively. The crude fiber and pigment content in the fruiting bodies cultivated from liquid fermentation was 12.9% and 740.21 µg/g, respectively, lower than those (15.4% and 867.45 µg/g, respectively) of the control. Temperature and pH exerted different effects on the pigment stability of the fruiting bodies cultivated from liquid and solid-state fermentations, while the time, oxidant (H₂O₂), reductant (vitamin C), and NaCl had similar effects on the samples cultivated in the two modes. [Conclusion] Liquid fermentation for the production of C. militaris fruiting bodies can not only shorten the production cycle but also improve the nutritional value, demonstrating great potential for industrial applications.

Abstract:[Background] Soil salinity is one of the main factors affecting maize yield, and endophytic fungi can significantly improve the resistance and growth of plants. Studying the endophytic fungi of maize is of great significance to increase maize yield. [Objective] To study the growth-promoting effects of endophytic fungi isolated from the roots of maize growing in the saline-alkaline land in Huanghua and the growth-promoting effects of the fungi on maize plants, so as to provide a theoretical basis and material support for increasing the maize yield in saline-alkaline land. [Methods] The tissue culture method was used to isolate endophytic fungi from the roots of maize. The seed soaking experiments were carried out to screen out the strains capable of promoting the germination of maize seeds under NaCl stress. The strains screened out were identified by morphological observation and molecular biological methods and characterized for the growth-promoting properties such as phosphorus- and potassium-solubilizing, indole-3-acetic acid (IAA)-secreting, and siderophore-producing abilities. Pot experiments were conducted to evaluate the effects of the strains on the biomass, plant height, root length, SPAD value, superoxide oxidase (SOD) activity, peroxidase (POD) activity, and malondialdehyde (MDA) content of maize plants under NaCl stress. [Results] A total of 25 strains of endophytic fungi were isolated from the roots of maize, among which the strains DYM7 and DYM11 significantly promoted the germination of maize seeds exposed to 0.15 mol/L NaCl, with the germination rate reaching 90%. DYM7 was identified as Setophoma terrestris and DYM11 as Exserohilum rostratum, both of which had the abilities of solubilizing potassium, producing siderophores, and secreting IAA. Under NaCl stress, strains DYM7 and DYM11 increased the plant height, root length, and SOD and POD activities and reduced the MDA content of maize. Moreover, strain DYM11 increased the aboveground dry weight and underground dry weight of maize plants by 16.43% and 22.17%, respectively, compared with the control. [Conclusion] The endophytic fungal strains capable of improving the salt tolerance and growth of maize by increasing the antioxidant enzyme activities, root length, and plant height, and decreasing the MDA content were screened out in this study. This study provides a theoretical basis and material support for the application of beneficial microbial in coastal saline-alkaline areas in improving the salt tolerance and yields of crops.

Abstract:[Background] Dark septate endophytes (DSEs) are representatives of endophytic fungi capable of enhancing the disease resistance and promoting the growth of plants. With wide distribution, culturability, and non-host specificity, DSEs demonstrate broad application prospects in agricultural production as well as environmental protection and restoration. [Objective] To screen the DSE strain(s) capable of controlling powdery mildew in bitter gourd (Momordica charantia) out of seven strains and investigate the effects of the strain(s) screened out on the phyllosphere bacterial community of M. charantia plants. [Methods] We carried out pot experiments with the seed soaking+soil spraying+root irrigation methods to study the effects of seven DSE strains on powdery mildew of M. charantia. The effects of the strain screened out on the seed germination and plant growth of M. charantia were studied by the seed soaking method. The 16S rRNA gene high-throughput sequencing was employed to reveal the structure of phyllosphere bacterial community in the early, middle, and late stages of powdery mildew in M. charantia inoculated with the strain screened out. [Results] The strain X22 (Ochroconis guangxiensis) was screened out as a potential biocontrol agent, with the control efficacy of 56.58% on powdery mildew of M. charantia. Compared with the non-inoculated control (O-), inoculation with X22 (O+) increased the seed germination rate and led to uniform seedlings. The inoculation increased the leaf number, stem diameter, SPAD, and plant height by 3.18%, 6.08%, 7.88%, and 22.59% (P<0.05), respectively. Compared with O-, O+ showcased increased alpha diversity of phyllosphere bacteria in the early, middle, and late stages of powdery mildew, while the abundance of phyllosphere bacteria in the O+ group presented an increase-decrease-increase trend. In all the stages of powdery mildew, neither the dominant phyla nor their relative abundance there were no significant differences between O- and O+ groups. In the early and middle stages of powdery mildew, the dominant genera and their relative abundance showed significant differences between the two groups. Specifically, beneficial bacterial genera such as Sideroxydans, Saccharomonospora, and Natronincola involved in the nitrogen cycle or with antimicrobial activity were enriched in the O+ group. [Conclusion] The DSE strain X22 exhibited good biocontrol effect on powdery mildew and promoted the seed germination and plant growth of M. charantia. It may regulate the community structure to maintain the diversity and stability of phyllosphere bacteria. Meanwhile, this strain can recruit beneficial bacteria with antimicrobial activity and nitrogen-fixing ability to inhibit pathogens and provide nitrogen sources for hosts to promote host growth, thereby improving host disease resistance. The strain X22 is a biocontrol agent with great potential for development and application.

Abstract:[Background] The frequent occurrence of drought in the world has seriously affected both the yield and quality of crops. An economically efficient method to alleviate it is urgently needed. Plant growth-promoting rhizobacteria (PGPR) are expected to directly improve drought tolerance in crops. [Objective] In arid environments, the species composition and distribution patterns of microbial communities are unique. It is essential to study the genetic diversity and functional diversity of bacteria screened from arid soils. [Methods] Thirty strains of Bacillus spp. and Burkholderia spp. were collected and isolated from the arid areas in Inner Mongolia and Hainan provinces, respectively. These strains were subjected to drought tolerance analysis and biological characteristic analysis using polyethylene glycol 6000 (PEG-6000) to simulate drought stress. [Results] Cluster analysis categorized the drought tolerance of the 30 tested strains into 3 groups. The tested strains exhibited 3 growth patterns under different stress conditions: in the first type of growth pattern, there was no significant difference in OD₆₀₀ value between the permeability potential of -0.2 mPa and 0 mPa; in the second type of growth pattern, the OD₆₀₀ value of the strain decreased as permeability potential increased, and the strains which exhibited this growth pattern represent 43.33% of the total tested strains; in the third type of growth pattern, there was no significant difference in OD₆₀₀ values at -0.6 mPa and -1.2 mPa permeation potential. The biological characteristics of the 30 tested strains revealed that each strain exhibited 1 to 4 characteristics of IAA, siderophore, urease, arginine decarboxylase, and biofilm, indicating the tested strains have potential plant growth-promoting functions. [Conclusion] Based on drought tolerance analysis and biological characteristic analysis, two superior drought resistance Bacillus strains, NC51 and NO89, were finally screened, both exhibiting the third type of growth pattern. These strains provide microbial resources for improving crop drought tolerance and developing microbial inoculants in the future.

Abstract:[Background] Stellaria dichotoma L. var. lanceolata Bge. is a perennial herb of Caryophyllaceae, with dried roots (Stellariae Radix) as the medicinal part. [Objective] To explore the changes of rhizosphere soil microbial community structure of S. dichotoma var. lanceolata planted for different years in genuine production area and the correlations of microbial community with soil physical and chemical factors and active components in Stellariae Radix. [Methods] Illumina high-throughput sequencing of bacterial 16S rRNA gene and fungal ITS sequences were performed to reveal the microbial community structures in the rhizosphere soil samples of S. dichotoma var. lanceolata planted for 1, 2, 3, and 7 years. The soil properties and the content of total flavonoids and total sterols in Stellariae Radix were determined by conventional methods. [Results] As the planting years of S. dichotoma var. lanceolate increased, the bacteria showed little change in the richness and increased diversity, while the fungi presented increased richness and diversity. The dominant bacteria were Actinobacteriota, Proteobacteria, and Chloroflexi, and the dominant fungi were Ascomycota and Basidiomycota in the rhizosphere soil. The dominant microbial genera varied significantly in the rhizosphere soil samples of S. dichotoma var. lanceolata planted for different years. In addition, the content of total sterols and total flavonoids in 3-year-old Stellariae Radix were significantly higher than those in the samples of other planting years. The correlation analysis showed that pH and alkali-hydrolyzable nitrogen had strong correlations with the microbial community in the rhizosphere soil. Amycolatopsis, Mortierella, Preussia, and Penicillium had significantly positive correlations with the main active components in Stellariae Radix. [Conclusion] The study preliminarily revealed the rhizosphere soil microorganisms related to the active components in Stellariae Radix, which provided a theoretical basis for the high-quality production of this herbal medicine.

Abstract:[Background] Trichoderma spp. have been widely used for controlling plant diseases. Trichoderma koningiopsis T-51, an effective biocontrol strain, is capable of promoting plant growth, inducing plant systemic resistance, and controlling plant diseases, demonstrating a promising prospect for practical applications. [Objective] To study and optimize the solid-state fermentation technology of T. koningiopsis T-51 for improving the spore production, and provide a theoretical reference for the large-scale production of this strain. [Methods] Single-factor experiments and response surface methodology were employed to screen the suitable fermentation substrate for strain T-51 and optimize the key fermentation factors including water content, fermentation duration, inoculation concentration, and carbon and nitrogen source composition. [Results] With rice husk as the fermentation substrate, the strain demonstrated the highest spore production. The water content of 75% and fermentation duration of 11 days significantly increased the spore production. In addition, an inoculation concentration of 1×10⁶ CFU/mL exhibited higher spore production, while the inoculation concentration of 1×10⁸ CFU/mL showed a decrease in sporulation. Glucose and ammonium sulfate were identified as the optimal carbon and nitrogen sources, respectively, for the spore production of strain T-51 with rice husk as the substrate. The fermentation parameters were optimized by the response surface methodology as water content of 79.5%, fermentation duration of 11 days, inoculation concentration of 1×10⁶ CFU/mL, 2.6% glucose, 0.75% lactose, and 5% ammonium sulfate. Under these optimized conditions, strain T-51 was predicted to achieve the maximum spore production of 7.76×10⁹ CFU/g, and the measured value was 7.83×10⁹ CFU/g. [Conclusion] This study has successfully established an efficient solid-state fermentation technology for strain T-51 with rice husk as the substrate, allowing adequate sporulation for field applications with reduced production costs. This study provided a theoretical basis for the future large-scale application of strain T-51 in the field.

Abstract:[Background] Root rot is widespread and harmful, being one of the most common diseases in the process of large-scale cultivation of Astragalus membranaceus in the northwest saline-alkali regions of China, which causes a decrease in yield and quality of A. membranaceus, and there is currently no effective control method. Trichoderma harzianum has a significant control effect on the pathogens causing root rot in rhizome crops, but its effect under saline-alkali conditions has been reported rarely. [Objective] To clarify the main pathogens causing root rot in A. membranaceus in the northwest saline-alkali areas of China, and to explore the inhibitory effect of T. harzianum EMF910 on these main pathogens under saline-alkali conditions. [Methods] The pathogens causing root rot of A. membranaceus in large-scale cultivation in the saline-alkali areas of northwest China were determined through tissue isolation, in vitro tie-back, morphological, and molecular biology methods. The inhibitory effect of T. harzianum EMF910 on these pathogens under saline-alkali conditions was studied through plate confrontation experiments. The control effect of T. harzianum EMF910 on root rot in A. astragalus in saline-alkali soil was investigated by pot experiment. [Results] The main pathogens causing root rot in A. astragalus in the northwest region were identified as Fusarium solani X12 and Fusarium obliquiseptatum P1. After culturing for 7 days under normal conditions (0% NaCl, pH natural), the plate inhibition rates of T. harzianum EMF910 on X12 and P1 reached 77.93% and 73.82%, respectively. After culturing for 7 days under saline-alkali conditions (1% NaCl, pH=8.5), the plate inhibition rates of T. harzianum EMF910 on X12 and P1 reached 70.22% and 67.95%, respectively. After culturing for 12 hours under normal conditions (0% NaCl, pH natural), the spore germination inhibition rates of T. harzianum EMF910 on X12 and P1 reached 87.21% and 86.11%, respectively. After culturing for 12 hours under saline-alkali conditions, the spore germination inhibition rates of T. harzianum EMF910 on X12 and P1 reached 72.29% and 64.47%, respectively. The pot experiments showed that in A. membranaceus pre-infected with root rot pathogens, the survival rate of A. membranaceus treated with T. harzianum EMF910 was 56.3%, while the survival rate of the control group treated with water without T. harzianum EMF910 was only 12.5%. The statistical survival rate of A. membranaceus with root rot showed that the incidence rate of root rot in T. harzianum EMF910 treatment group was 33.3%, while that in the water control group without T. harzianum EMF910 was 50.0%. [Conclusion] The main pathogens causing root rot in A. mezmbranaceus in the northwest saline-alkali areas of China are mainly F. solani and F. obliquiseptatum. T. harzianum EMF910 can effectively inhibit the growth and spore germination of these pathogens under saline-alkali conditions (1% NaCl, pH 8.5), but the inhibitory effect is lower compared to that under normal conditions (0% NaCl, pH natural). T. harzianum EMF910 has a good control effect on root rot in A. membranaceus in saline-alkali soil. These results provide data support for the biological control of root rot in A. membranaceus in saline-alkali areas of Ningxia using T. harzianum EMF910 and also provide a reference for the use of T. harzianum EMF910 to control the root rot in other saline-alkali areas of China.

Abstract:[Background] Fungi produce diverse secondary metabolites to adapt to their habitats. [Objective] To compare the secondary metabolites of Eurotium cristatum strains from two habitats (Fuzhuan brick tea and ocean) in PDA and explore the regulatory effect and mechanism of the tea leaf medium on the metabolites of ocean originated E. cristatum. [Methods] Liquid chromatography-mass spectrometry combined with feature-based molecular networking was employed to analyze the differences of secondary metabolites of the two strains of E. cristatum, and the changes in non-volatile metabolites of the ocean originated strain in the tea leaf medium were analyzed by the multivariate statistical method. In addition, we investigated the effects of indirect and direct carbon sources on the secondary metabolites of the ocean originated strain. [Results] Firstly, the two strains of E. cristatum presented similar polyketone synthesis capacity but significant differences in non-ribosomal peptide synthesis. Specifically, the tea-derived strain produced isopentenyl cyclic dipeptide, while the ocean originated strain produced oligopeptides. Secondly, the domestication in the tea leaf medium for 5 days induced changes in the secondary metabolic pathways of the ocean originated strain. Finally, some metabolites of the ocean originated strain in the tea leaf medium were identical to those in the medium with indirect carbon source. [Conclusion] There were significant differences in the secondary metabolic pathways between E. cristatum strains from the two habitats. The short-term domestication in the tea leaf medium changes the secondary metabolic pathways of the ocean originated strain, which may be partly due to the lifting of carbon catabolite repression.

Abstract:[Background] Forest musk deer are valuable economic animals in China. Captive musk deer populations frequently suffer from bacterial diseases, and thus studying the related pathogens is of great significance for the prevention and control of diseases attacking forest musk deer. [Objective] To investigate the drug resistance and pathogenicity of the microorganisms causing the death of a forest musk deer. [Methods] Bacteria were isolated from a deceased musk deer and identified. The drug susceptibility, pathogenicity in mice, and resistance gene and virulence genes of the isolates were studied. [Results] The forest musk deer suffered from mixed infection of Staphylococcus lentus (named 23HYSL) and Escherichia coli (named strain 23HYEC). The strain 23HYSL was resistant to aztreonam, lincomycin, tetracycline, and sulfisoxazole, while strain 23HYEC was a multi-drug resistant E. coli strain producing extended-spectrum β-lactamases. The median lethal doses (LD₅₀) of strain 23HYSL and strain 23HYEC in mice were 1.39×108 CFU and 8.97×107 CFU, respectively. The pathological sections showed that the mixed infection caused severer spleen lesions and facilitated the colonization of strain 23HYEC in the heart and liver of mice. Both strains carried the resistance genes sul2, tetA, tetC, bla_TEM, and bla_CTX-M. In addition, strain 23HYSL carried the virulence gene clfa, while strain 23HYEC carried 5 virulence genes including astA. [Conclusion] We isolated S. lentus from forest musk deer for the first time and studied the drug resistance and pathogenicity of this bacterium in the case of mixed infection with astA⁺ E. coli, giving insights into the prevention of related diseases and the rational use of drugs.

Abstract:[Background] As foodborne pathogens, Cronobacter spp. often appear in the reports of neonatal illness. So far, there has been no report of Cronobacter spp. in forest musk deer. [Objective] We identified and sequenced a strain of Cronobacter malonaticus isolated from the kidney of forest musk deer, aiming to lay a foundation for the prevention and treatment of related diseases in forest musk deer. [Methods] After the pathogen was isolated, biochemical tests, drug susceptibility tests, pathogenicity test in mice, and whole genome sequencing were conducted. Based on the sequencing results, the population evolution analysis, species typing, and gene function annotation were performed. [Results] The pathogen was identified as C. malonaticus based on the average nucleotide identity (ANI) and phylogenetic tree, with the biochemical test results consistent with the general characteristics of C. malonaticus. The strain, named Dcc0527, was sensitive to some quinolones, amphenicols, aminoglycosides, and β-lactams and resistant to some sulfonamides and macrolides. The results of whole genome sequencing showed that the strain contained one ring chromosome and four ring plasmids, with the whole genome size of 1 257 547 026 bp and the G+C content of 57.08%. The multilocus sequence typing showed that the strain presented the sequence type ST211. The genome of strain Dcc0527 carried the genes conferring resistance to several antibiotics, such as elfamycin, fluoroquinolone, and tetracycline and several virulence genes, such as Type IV pili, kpsD, and iroN. In addition, there were three complete phage regions in the chromosome and plasmids of strain Dcc0527. [Conclusion] We isolated a strain of C. malonaticus from the kidney of forest musk deer and obtained the whole genome sequence of this strain (ST211). The findings provide reference for the prevention and control of bacterial diseases in forest musk deer.

Abstract:[Background] Mycoplasma galliscepticum (MG) is the main cause of chronic respiratory diseases in poultry. The different susceptibility to antibiotics and pathogenicity of MG strains from different regions increases the difficulty in the prevention and control of MG infection. [Objective] To clarify the genotypes, antibiotic resistance, resistance gene mutations, and pathogenicity of MG isolates from a chicken farm in Yantai, Shandong, so as to provide a scientific basis for the prevention and control of MG in this area. [Methods] The MG isolates were obtained from the cleft palate swabs of chicken tested positive for MG. Seven housekeeping genes (atpG, plsC, mraW, ugpA, DUF3196, lgT, and dppC) were used for multilocus sequence typing (MLST), and a phylogenetic tree was constructed. The minimum inhibitory concentrations (MICs) of eight antibiotics including chlortetracycline, spectinomycin, lincomycin, tylosin, tylvalosin, tiamulin, valnemulin, and doxycycline against the isolates were determined. The 23S rRNA V domain and L4 and L22 protein genes were sequenced. SPF-grade chickens of 28 days old were infected by eye challenge and trachea challenge, respectively. [Results] Nine MG isolates were obtained in this study, including seven isolates (YTX2, YTX5.6, YTX11, YTX12, YTX13, YTX14, and YTX15) of sequence type 97 (ST97) and two isolates (YTX9 and YTX10) of ST16. New alleles of plsC and mraW were identified in the seven strains of ST97, with the ID of 33 and 31, respectively. All the MG isolates were sensitive to valnemulin and tiamulin (MIC≤0.25 μg/mL), moderately sensitive to tylvalosin and doxycycline (MIC≤4 μg/mL), and resistant to chlortetracycline and lincomycin (MIC≥16 μg/mL). The seven MG isolates of ST97 were moderately resistant to tylosin (MIC: 4-8 μg/mL). The mutation A2069G was identified in the V domain of the 23S rRNA gene in strains YTX5.6 and YTX2. The mutation G568T occurred in the L4 protein gene of strains YTX5.6 and YTX2, and the mutations T102C, T129C, T252C, C336T, and G404A occurred in the L22 protein gene. The strain YTX10 sensitive to tylosin, tylvalosin, tiamulin, valnemulin, and doxycycline showed the same sequence compared with the control strain MG R_low, with no mutation detected. The morbidity of air sacculitis was 80%, 60%, and 80%, respectively, 10, 20, and 30 days after tracheal challenge with the strain YTX5.6. Air sacculitis occurred 20 and 30 days after tracheal challenge with YTX10, with the morbidity of 40% and 20%, respectively. The tracheal mucosal thickening was severer in the tracheal challenge group than in the eye challenge group (P<0.05). Severe tracheal thickening was observed 20 days after tracheal challenge with strain YTX5.6, with an average thickness of 300.6 μm. Tracheal challenge with strain YTX5.6 or YTX10 resulted in significantly higher MG loads than eye challenge with same strain 10, 20, and 30 days post-infection. [Conclusion] In this study, nine MG strains of ST97 and ST16 were isolated from a chicken farm in Yantai, Shandong. The nine isolates demonstrated varied resistance to antibiotics and different pathogenicity to SPF-grade chickens.

Abstract:[Background] Salmonella is a zoonotic pathogen and one of the most common pathogens causing infectious diarrhea in humans. [Objective] To analyze the serotypes, drug resistance, and multilocus sequence types of 176 Salmonella strains isolated in Suzhou, 2023. [Methods] The serotypes of the isolates were identified by the slide agglutination method. The drug resistance was tested by the micro-broth dilution method. The multilocus sequence typing (MLST) was performed by whole genome sequencing, and the sequencing results were compared with PubMLST to obtain the sequence types (STs) of the strains. [Results] A total of 42 serotypes belonging to 9 serogroups were identified for the 176 Salmonella isolates. The dominant serotypes were Salmonella enteritidis (26.70%) and Salmonella typhimurium (18.75%). The resistance rate of the 176 strains to ampicillin was the highest (60.23%), followed by that to streptomycin (47.16%). All the strains were sensitive to ceftazidime/avibactam, meropenem, ertapenem, and amikacin. The multidrug resistance (MDR) of the 176 strains reached a rate of 57.39%, with 51 patterns (including 18 patterns involving penicillins+ β-lactam/ β-lactam inhibitor complex+cephalosporins). The 176 strains presented 43 STs, among which ST11, ST34, and ST19 were the top three, with the detection rates of 27.27%, 10.80% and 7.95%, respectively. [Conclusion] The Salmonella strains in Suzhou present diverse serotypes and STs. The dominant serotypes are S. enteritidis and S. typhimurium, and the dominant ST is ST11. The MDR phenomenon is serious and thus surveillance should be strengthened.

Abstract:[Background] Mole crickets (Gryllotalpa spp.) are widely distributed agricultural underground pests in China, and the composition of their gut bacteria and the functional bacterial resources remain to be studied. [Objective] To obtain the culturable bacteria from the gut of G. orientalis, screen out the strains capable of producing cellulase, measure the cellulase activities of the strains, and explore the culture conditions of the strains with high cellulase activities. [Methods] The gut bacteria of G. orientalis were isolated by the culture method and identified by methods of molecular biology. The cellulose-producing strains were screened by the carboxymethylcellulose sodium (CMC-Na) hydrolysis assay, and the cellulase activity was determined by the 3,5-dinitrosalicylic acid (DNS) method. [Results] A total of 23 strains were isolated from the gut of G. orientalis, belonging to 10 species of 7 genera (4 species of Bacillus and 1 species of Enterococcus, Staphylococcus, Acinetobacter, Proteus, Enterobacter, and Lactococcus, respectively). The results showed that all the 22 strains except strain N18 had cellulase-producing capacity, among which strains N3 and N14 had the strongest cellulase-producing capacity, followed by N15 and N21. The medium pH, culture time, and inoculum amount had different effects on the cellulase production. Within the ranges set in this study, strains N3 and N14 always had the highest cellulase production under the influences of different single factors. [Conclusion] The gut of G. orientalis harbors rich culturable bacterial resources, and 95% of the isolates of gut bacteria have the function of producing cellulase. Among the isolates, Bacillus subtilis N3 and N14 with the highest cellulase production demonstrate the most potential for development.

Abstract:[Background] The renaming of “microbiome” signifies changes in the conceptual understanding and research methodologies of microbiomes. [Objective] To understand the development status and differences in the field of microbiomes around the world and provide countermeasures and suggestions for China to promote the research and development of microbiomes. [Methods] On the basis of the results from policy research, bibliometrics, and patent analysis, this paper compares the status of the microbiome field around the globe from four aspects: strategic environment, basic research, patent layout, and clinical translation. [Results] The global strategic layout of microbiomes was led by the United States, Canada, and the European Union. The basic research in this field has gradually deepened, and the patented technology has entered a stage of rapid development. However, the clinical translation of research results was insufficient. China started late in the research on microbiomes but demonstrated rapidly increasing basic studies and patents. [Conclusion] In light of these results, three suggestions are proposed to accelerate the development of microbiome research and application in improving one health in China. The three suggestions are establishing a regulatory system aligned with development of the healthy industry, strengthening the role of microbiome enterprises as innovation leaders, and fostering talent pipelines in the microbiome and one health fields.

Abstract:To improve the training quality of undergraduates, this paper analyzes the background, necessity and feasibility of the construction of specialized innovation and integration courses in microbiology, taking “Internet plus” innovation and entrepreneurship competition as the starting point. The reform measures implemented by the Microbiology curriculum team for the integration of competition and teaching include: (1) Building a strong practice and interdisciplinary innovation and entrepreneurship resource base, and practicing value guidance through the integration of creativity and innovation; (2) Established a “student-centered” mixed teaching model to guide students to learn actively; (3) To establish a composite team of teachers to provide intellectual support for the reform of the integration of competition and education; (4) Establish a diversified scientific and reasonable evaluation model, which is in line with the talent evaluation standards of enterprises. This paper also expounds the concrete implementation of the integration of competition and education from the perspectives of the project cultivation, selection and guidance of competition practice of “Internet plus” competition. Then, it analyzes the effect of the integration of competition and teaching by means of questionnaire survey, suggesting that the integration of competition and teaching improves students’ comprehensive qualities such as innovative ability and entrepreneurial thinking, ability to analyze and solve complex problems, social responsibility, and promotes the high-quality development of undergraduate education on the whole. This model achieves the goal of innovative, advanced and challenging first-class undergraduate course teaching, and achieves the “trinity” education effect of knowledge impartation, ability cultivation and curriculum ideological and political quality improvement, which has reference and promotion value for local undergraduate colleges and universities to cultivate applied talents.