Abstract:[Background] Polyketides have important applications in the pharmaceutical field, and the development of related drugs relies on the variable structural knowledge of polyketide synthases. The structural and catalytic mechanism of human fatty acid synthase are similar to those of polyketide synthase, and the study of human fatty acid synthase structure can lay the foundation for the study of polyketide synthase. [Objective] We worked on the expression of purified human fatty acid synthase protein in Saccharomyces cerevisiae and determined suitable in vitro purification conditions. [Methods] The recombinant plasmid with His and Strep dual affinity chromatography tags was constructed using Saccharomyces cerevisiae BJ5464 as the expression vector, and the target protein was purified by affinity chromatography after the protein overexpression, and the suitable protein purification conditions were determined by gel electrophoresis results. [Results] The recombinant expression plasmid pxw55-hfas-cSHII was successfully constructed and the human fatty acid synthase was purified in vitro. Preliminary screening under different buffer conditions was tried and the appropriate protein purification system was determined by combining with the feedback of electron microscope observation results. [Conclusion] Structural analysis by electron microscopy requires high protein purity, suitable concentration and correct conformation of protein samples. The construction of the purification system and the determination of the purification conditions of human fatty acid synthase provided a good sample for the analysis of the structure of human fatty acid synthase, and pave the way for the analysis of the similar but more complicated polyketide synthase.

Abstract:[Background] Vibrio alginolyticus infects fish, shrimp, shellfish, and other economic marine animals, which has brought great economic losses to the mariculture industry and posed a great threat to public health and food safety. [Objective] The study aims to investigate the inhibitory effect of Fructus mume on V. alginolyticus and the mechanism, which is expected to lay a theoretical basis for the further development and utilization of F. mume. [Methods] The minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of F. mume extracts (FME) on V. alginolyticus were determined with the tube double dilution method, the relative conductivity of V. alginolyticus by a conductivity meter, and the nucleic acid leakage, respiratory chain dehydrogenase activity, and biofilm inhibition rate of V. alginolyticus by spectrophotometry. The protein synthesis of V. alginolyticus was analyzed by electrophoresis, and the submicroscopic structure of it was observed under a scanning electron microscope. [Results] The MIC and MBC of FME on V. alginolyticus were 1.953 mg/mL and 3.906 mg/mL, respectively. FME significantly increased the relative conductivity and nucleic acid leakage, significantly reduced the protein synthesis, and had great impact on the submicroscopic morphology of V. alginolyticus. Meanwhile, FME significantly inhibited the biofilm formation and the respiratory chain dehydrogenase activity of it. [Conclusion] The FME coould inhibit and even kill V. alginolyticus by increasing the membrane permeability, inhibiting the biofilm formation, respiratory chain dehydrogenase activity, and protein synthesis of V. alginolyticus.

Abstract:[Background] Metal selenides have attracted increasing attention in semiconductor, electrochemistry and anticancer fields due to its excellent photoelectric and catalytic properties. Compared with the traditional chemical methods, biosynthesis of metal selenides is environmentally friendly and lower energy. However, few studies on the biosynthesis of metal selenides were reported, and its relevant mechanisms were still unclear. [Objective] We chose Mariannaea sp. HJ to synthesize three kinds of metal selenides and proposed the possible mechanisms. [Methods] X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to initially characterize the metal selenides synthesized by strain HJ. The changes in total sulfhydryl content, total antioxidant capacity and free radical content were investigated during the synthesis process. Besides, the function of transporter DMT1 was also verified in the synthesis of metal selenides. [Results] XRD results showed that Bi₄Se₃, PbSe and CoSe₂ nanoparticles could be separately biosynthesized by strain HJ under the action of Bi³⁺, Pb²⁺, Co²⁺ and SeO₃^2-, and the optimal pH conditions for their synthesis were 6.0, 7.0, and 8.0, respectively. FTIR analysis illustrated that these nanoparticles were covered with certain functional groups such as amino, carboxyl and hydroxyl groups. Compared to the control group, it was also found that the total sulfhydryl concentration was significantly reduced during the synthesis process, while the total antioxidant performance was increased. It was indicated that the sulfhydryl system or the non-enzymatic system of amino acid metalloproteins could be involved in the reduction of SeO₃^2-. The benzylisothioureas shielding experiment showed that metal transporter DMT1 played a key role in SeO₃^2- transportation and metal selenides secretion. Besides, oxidative stress was produced after the addition of Bi³⁺, Pb²⁺and Co²⁺, which caused strain HJ to secrete more hydrogen peroxide, hydroxyl free radicals and superoxide free radicals outside the cells. The transportation process of metal ions or nanoparticles could be enhanced by above free radicals through inducing heat shock effects. [Conclusion] Mariannaea sp. HJ could greenly synthesize Bi₄Se₃, PbSe and CoSe₂ nanoparticles. This study would provide useful information for biosynthesis and mechanism of metal selenides.

Abstract:[Background] Harmful algal blooms (HABs) in coastal waters can significantly change the composition of microbial community, thereby affecting the cycling of carbon and nitrogen in the ocean. Fungi are important decomposers in the ocean, but the impact of HABs on fungal community has not been elucidated. [Objective] Clarifying the influence of HABs on the fungal community is of great importance for further explaining the effect of HABs on material cycle in the ecosystem. [Methods] Through ITS1 amplicon sequencing, we analyzed the response of fungal community to an early-spring diatom bloom in 2017, in order to investigate the dynamic and co-occurrence patterns of the community. [Results] The alpha diversity indices of the fungal community changed significantly among four bloom stages, and they were all correlated with phosphate, nitrate, and nitrite (P<0.05). At the phylum level, the fungal community was dominated by Ascomycota (relative abundance:90.2%) and Basidiomycota (8.27%), among which Ascomycota was dominant across the four stages. At the class level, fungi from Leotiomycetes (16.1%) and Eurotiomycetes (9.3%) were the most abundant. The succession of fungal community was mainly driven by the abundance of harmful algal species, but changes in environmental factors including nitrate, nitrite, and phosphate were also responsible. Co-occurrence network was mainly composed of Helotiales, Eurotiales, Xylariales, Saccharomycetales, and Agaricostilbales. [Conclusion] The fungal community demonstrated obvious succession during the diatom bloom, which was mainly induced by diatom abundance, as well as environmental factors. The interaction of the fungal community within group was stronger than that between groups during the bloom, which is important for maintaining community stability.

Abstract:[Background] Efficient bioleaching is closely related to the active iron and sulfur metabolism mediated by microorganisms. Thus, the lack of iron metabolism will restrict low-grade chalcocite bioleaching. [Objective] To improve the bioleaching of low-grade chalcocite by enhancing iron and sulfur metabolism and the "contact". [Methods] The iron-oxidizing Leptospirillum ferriphilum (screened with the double-plate method), iron-reducing Acidiphilium sp., sulfur-oxidizing Acidithiobacillus caldus, and the Fe²⁺/Fe³⁺-pyrite-fibrous waste acid hydrolysate system (waste utilization) were combined to improve low-grade chalcocite bioleaching. [Results] A large number of micropores and pits were observed on the slag surface under the scanning electron microscope (SEM), suggesting the active action of the bacteria. Fourier transform infrared (FTIR) spectroscopy revealed that bonds such as N-H, C=O, and O-H were closely related to extracellular polymer substance (EPS), and significantly enhanced absorption peaks of S=O and C-O-S testified more intense sulfur metabolism. Confocal laser scanning microscope (CLSM) manifested that more attached cells and EPS existed in the optimized system, laying the foundation for the "contact" mechanism. After 40 days of leaching, the concentration of planktonic and attached cells increased by 2.51 and 5.73 times, respectively. The maximum specific growth rate (μ_max) appeared 1.5-5.3 days earlier, and the highest cupric ion leaching rate reached 67.6%. [Conclusion] The intervention of iron-oxidizing bacteria, iron-reducing bacteria, and exogenous iron-containing substances strengthens the iron and sulfur metabolism of the leaching system and accelerates the dissolution of minerals. The acid hydrolysate promotes iron circulation and the growth of bacteria. The increase in the number of attached cells and secreted EPS enhances the "contact", thus effectively improving the bioleaching microenvironment and efficiency.

Abstract:[Background] Bacteria can synthesize polyhydroxyalkanoates (PHA) as intracellular carbon and energy storage compounds in order to better adapt to the environment. In mangroves, the soil is periodically submerged by seawater, which forms a special habitat with abundant nutrients and fluctuating contents, providing conditions for bacteria to evolve a special PHA synthesis pathway. [Objective] In order to improve the understanding of PHA-producing bacterial resources, we isolated and identified the PHA-producing bacteria, and evaluated their ability to produce PHA. [Methods] We collected soil samples from shoal and Sonneratia caseolaris rhizosphere, isolated bacteria during the 5 weeks of incubation, identified them by 16S rRNA gene sequence similarity and phylogenetic tree, and determined the PHA producing ability by testing the PHA synthase gene (phaC). Based on the draft genome sequence data, we determined the class of phaC gene, the metabolic pathways and the phylogenetic relationship among different strains. We analyzed the PHA content and composition using gas chromatography. [Results] A total of 97 strains of bacteria were isolated, among which 13 strains were PHA-producing bacteria, including Cytobacillus firmus, Bacillus flexus, Marinobacter hydrocarbonoclasticus and Microbacterium esteraromaticum. B. flexus MN15-19 using pyruvate as the sole carbon source could accumulate 11% PHA per dry cell weight. This strain had reverse tricarboxylic acid cycle, which is considered as carbon fixation pathway. Therefore, based on B. flexus MN15-19, PHA production technique directly using CO₂ could be developed. Mi. esteraromaticum was a PHA-producing bacterium, whose phaC gene was too unique to be identified as any known phaC genes. [Conclusion] Bacteria isolated from mangrove ecosystem have unknown PHA synthase pathway, which indicates that mangrove bacterial biological resources deserve further study.

Abstract:[Background] The activity of Nitrosomonas was significantly influenced by NH₃-N concentration, but the inhibition kinetics of NH₃-N concentration of the adhesive Nitrosomonas were still unknown. [Objective] The influence of NH₃-N concentration on 3 strains of adhesive Nitrosomonas (Nitrosomonas eutropha CZ-4, Nitrosomonas halophila C-19 and Nitrosomonas europaea SH-3). [Methods] Three strains of Nitrosomonas (N. eutropha CZ-4, N. halophila C-19 and N. europaea SH-3) were cultured under different initial NH₃-N concentrations (ranged from 25-1 000 NH₃-N mg/L) with calcium carbonate as the adsorption matrix. The accumulation rate of NO₂^--N and the specific growth rate were measured, the inhibition kinetic equations of ammonia oxidation were also established by Edwares2 model. [Results] The accumulation of NO₂^--N of N. halophila C-19 was fastest when the initial NH₃-N concentration was 50-100 mg/L, while the NO₂^--N accumulation rate was maximum when the initial NH₃-N concentration was 50-200 mg/L for N. europaea SH-3 and 50-400 mg/L for N. eutropha CZ-4, respectively. The maximum specific growth rate of N. eutropha CZ-4 occurred at the initial NH₃-N concentration of 50-400 mg/L, which was much higher than N. halophila C-19 (25-100 mg/L). There was no significant difference in growth rates for N. europaea SH-3 when the initial NH₃-N concentration ranged from 50 mg/L to 800 mg/L. The K_I of N. europaea SH-3 (922.76 mg/L) was significantly higher than N. eutropha CZ-4 (597.88 mg/L), and also the K_I of N. eutropha CZ-4 was significantly higher than N. halophila C-19 (186.24 mg/L). Moreover, the K_m (72.06 mg/L) of N. europaea SH-3 was significantly higher than N. halophila C-19 (23.23 mg/L). [Conclusion] The three strains of adhesive Nitrosomonas showed great differences both in ammonia oxidation activity and growth. The results may not only help to understand the functions of different Nitrosomonas in wastewaters with different NH₃-N concentrations, but also contribute to develop corresponding engineering technologies.

Abstract:[Background] Environmental estrogens, major components in the new types of environmental pollutants, threaten the health of humans and animals by their adverse effect on the functions of the endocrine system. Microbial degradation is considered an efficient method in the removal of estrogenics and the bioremediation of polluted environments. [Objective] To improve diethylstilbestrol (DES) biodegradation efficiency, we studied the degradation characteristics of a DES-degrading bacterium Serratia sp. AXJ-M. [Methods] The degradation conditions of DES by Serratia sp. AXJ-M were optimized by performing the single factor test, Plackett-Burman test, steepest ascent hill climb test, and Box-Behnken test. [Results] Application of (NH₄)₂SO₄, ZnCl₂, and tryptone as inorganic nitrogen sources, additional metal ions, and added nutrients, respectively, significantly promoted the degradation of DES. The concentration of ammonium sulfate and DES and pH value were selected as the key parameters affecting the degradation of DES by performing the Plackett-Burman experiment. Box-Behnken experiment design and response surface methodology (RSM) analysis were adopted, the optimized conditions were (NH₄)₂SO₄ 1.48 g/L, ZnCl₂ 0.02 g/L, culture temperature 30℃, pH 7.19, DES 119.5 mg/L, and inoculation biomass 3%. The degradation rate of DES under these conditions reached 76.89% within 7 d, which was 17.38% higher than initial conditions. [Conclusion] Serratia sp. AXJ-M, a highly efficient DES degrading strain, can be used as an excellent microbial resource for bioremediation of the environment polluted by DES or other synthetic estrogens.

Abstract:[Background] Polycyclic aromatic hydrocarbons (PAHs) accumulated in agricultural soils are threatening human health and ecosystem via food chain. The strategy to impede PAHs entrance by biofilm formation of degrading bacteria on the root surface is economically feasible. Bacteria cell properties are the key factors determining its adhesion and initial formation of the biofilm. [Objective] Our study aims to investigate the biofilm formation process and identify the features of a phenanthrene degrading bacterium Pseudomonas sp. JM2-gfp influencing on the cell adhesion and the biofilm formation, to observe its colonization on the wheat root surface, and finally to provide references for building a control barrier in the soil-rhizosphere system.[Methods] Methods of petri dish culture observation, crystal violet stain, and contact angle assay were used to determine the cell characteristics of JM2-gfp. Hydroponic culture of plant was used to generate the biofilm formation. The structural features of the biofilm were observed and analyzed by a confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM). [Results] The strain Pseudomonas sp. JM2-gfp has a flagella structure and hydrophobic cell wall, as well as strong motility, initial adhesion, self-aggregation ability. It showed good biofilm-forming abilities and phenanthrene-degrading performance. Compared with planktonic bacteria, our biofilms can degrade phenanthrene within 48 hours by 2.5 times. The film formation process presented obvious periodic changes, and the amount of the biofilm reached the maximum at the second day. The thickness of the biofilm within 2 days was about 32.8 μm, and a variety of extracellular polymeric substances (EPS) were secreted on the biofilm, containing carbohydrate at the concentration of 74.68 μg/mL and protein 211.9 μg/mL, respectively. After 4 days of co-cultivation of wheat roots and JM2-gfp, a stable biofilm was formed by JM2-gfp on the root surface, and further colonized the roots, stems and leaf tissues. [Conclusion] The phenanthrene degrading bacterium Pseudomonas sp. JM2-gfp can form stable biofilms and enhance its degradation abilities. The formation of biofilm on the root surface provides an alternative approach in future applications to prevent organic pollutants entering into the crops.

Abstract:[Background] Heavy metal contamination of agricultural soil is an environmental problem as a result of anthropogenic activities. Cadmium (Cd), one of the most toxic heavy metals, poses health risks to both human being and the ecosystem. [Objective] Aiming at laying a theoretical basis for bioremediation and health risk assessment of Cd, we explored the effect of different levels of Cd on soil (rhizosphere and bulk soil) fungal communities of two oilseed rape species (Brassica napus and B. juncea). [Methods] Through high-throughput sequencing of fungal ribosomal internal transcribed spacer (ITS), the impact of Cd on soil fungal communities of the two species was evaluated. [Results] Cd stress changed the composition and structure of soil fungal communities, but had no significant influence on the alpha diversity of them. Soil Cd concentration and biomass were in significant correlation with the rhizosphere soil fungal communities of the two species and the fungal community of B. juncea bulk soil was significantly correlated with Cd concentration. The molecular ecological networks of soil fungal communities were also affected by Cd pollution, as manifested by the reduced stability and symbiosis of the networks for the fungal communities of B. napus rhizosphere soil, improved stability and attenuated symbiosis of the networks for the fungal communities of B. napus bulk soil, and increased stability and symbiosis of the networks for fungal communities of B. juncea rhizosphere and bulk soil. [Conclusion] Cd pollution influences the indigenous fungal community in soil, which might further change soil ecosystem functions.

Abstract:[Background] 1,3-Dimethyl-2-imidazolidinone (DMI) is a nonproton solvent with strong polarity, which remains steadily in waste water from production and application processes and causes potential hazard to people's health. [Objective] Acquisition of DMI degrading microbial strains. [Methods] Isolation and screen of DMI degrading microbial strains from the soil of manufacture plant by DMI tolerance assay. The strains were identified by morphological features and 16S rRNA gene sequence analysis. [Results] Two putative Bacillus velezensis strains tolerant to 5% (V/V) DMI were isolated from the soil samples, which were designated as DT-1 and DT-2 respectively. Both the whole cells and the cell-free extracts could reduce the DMI levels in the reaction systems. The degrading rates of whole cells and cell-free extract of strain DT-1 reached 48% and 68% respectively at 1% (V/V) DMI concentration. [Conclusion] DMI degrading Bacillus strains were obtained, which provided a basis for microbial degradation of DMI in the polluted environments. Moreover, the results in this study expand our knowledge of the biological function of Bacillus.

Abstract:[Background] Catalase (CAT) is involved in the growth and development of fungi and protects them from oxidative damage in the event of stress. [Objective] The VvCAT1 gene from Volvariella volvacea was expressed in Escherichia coli Stbl3 and its temperature tolerance was characterized. [Methods] VvCAT1 was cloned to construct a recombinant plasmid pBAR GPE1/VvCAT1 which was then transformed into Stbl3 to yield a recombinant strain expressing catalase. Catalase activity and growth of the recombinant strain (pBAR GPE1/VvCAT1/Stbl3) and the control strain (pBAR GPE1/Stbl3) were measured to verify the temperature tolerance. [Results] The recombinant strain exhibited stronger heat and cold tolerance than the control with increased catalase activity and better growth. [Conclusion] The transgenosis and expression of VvCAT1 significantly improved the heat and cold tolerance of E. coli Stbl3.

Abstract:[Background] The Gram-negative Pasteurella multocida (Pm) causes respiratory diseases and septicemia in animal and human. Capsular type A Pm HN02 has been isolated and identified by our laboratory. [Objective] We sequenced the whole genome of HN02 and analyzed the bioinformation, thereby supplementing the genome information of Pm. Through identification and phylogenetic analysis, the virulence genes and genetic evolution of the strain were clarified, respectively, which laid a theoretical basis for clinical prevention and diagnosis of related diseases. [Methods] The whole genome of HN02 was sequenced by SMRT and corrected by Illumina sequencing, followed by genome annotation and bioinformatics analysis. The virulence genes were identified by PCR and the phylogenetic tree was constructed for analysis. [Results] The whole genome of HN02 was 2 333 292 bp, with GC content of 40.15mol%. It was predicted to have 2 389 coding genes, including 19 rRNA genes (6 23S rRNA, 6 16S rRNA, and 7 5S rRNA genes), 62 tRNA genes, and 5 sRNA genes, 84 tandem repeats, 66 minisatellite DNAs, 2 microsatellite DNAs, 9 genomic islands, and 9 prophages. A total of 1 648, 2 190, and 1 917 genes were annotated in Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Cluster of Orthologous Groups of proteins (COG), respectively. Most of them were involved in the metabolic process of Pm. In addition, 85 type III secretion system effector genes, 191 phenotypic mutation genes, 165 virulence factor-related genes, and 1 important secondary metabolism gene cluster were identified. According to the analysis result, a circular map for the genome was plotted, and the genome information was submitted to NCBI to obtain the accession number cp037865. PCR identification showed that the strain had 14 virulence genes such as fimA and toxA and deleted virulence genes such as tadD. Phylogenetic analysis suggested that HN02 had the closest genetic relationship with the strain (MH150895.1) from Beijing. [Conclusion] the whole-genome sequence and biological characteristics of capsular type A Pm HN02 were elucidated and the evolutionary relationship was revealed, providing a reference for preventing the epidemic of Pm-induced disease and exploring the underlying pathogenic mechanism.

Abstract:[Background] The effective colonization of biocontrol bacteria in crop roots is the prerequisite for their functions, and intuitive tracking technology and effective quantitative methods are important tools for studying the roots' distribution of biocontrol bacteria.[Objective] To study the colonization characteristics of QHZ11 (antagonistic bacteria of Rhizoctonia solani JT18) in potato plants and its growth-promoting effect on potato. [Methods] Using green fluorescent protein (GFP) to label QHZ11, and separately inoculating the labeled bacterial suspension, bio-organic fertilizer and sterile water into the sterilized soil. Using laser confocal microscopy technology and real-time fluorescent quantitative PCR to study the colonization characteristics and quantitative changes of labeled strain in different parts of potato plants and its growth-promoting effect on potato. [Results] The pHAPII plasmid was successfully transformed into QHZ11 and could be inherited stably for 40 generations in QHZ11-gfp, recorded as QHZ11-gfp; the colony morphology, growth curve and antagonistic ability against R. solani JT18 of strain before and after the labeling were basically same. Starting from the 7th day, green fluorescence successively were found on the potato buds and roots, indicating that QHZ11-gfp successfully colonized on the potato buds, roots, etc. The quantity of colonization of QHZ11-gfp in the roots and stolons both showed a trend of first increasing to the peak in tuber formation period and then decreasing and in the whole growth period, the quantity of colonization of QHZ11-gfp in the roots was always>stolons. Both bacterial suspension and bio-organic fertilizer treatments significantly promoted the growth of potato roots, increased the tuber yield by increasing plant height, etc. The fluorescence intensity, the quantity of colonization and the growth-promoting effect on potato of bio-organic fertilizer treatment were significantly better than those of bacterial suspension. [Conclusion] QHZ11-gfp can be successfully colonized on potato plants and has a good growth-promoting effect on potatoes. Making it into bio-organic fertilizer promotes its colonization and makes the growth-promoting effect better.

Abstract:[Background] Potato black scurf is a typical soil-borne disease caused by Rhizoctonia solani. At present, the bacterial resources for biological control of the disease are relatively limited, and the researches on the biological control mechanisms of corresponding strains are more lacking. [Objective] To clarify the biocontrol effect of QHZ11-an antagonistic bacteria of Rhizoctonia solani JT18, and reveal its partial biological control mechanisms on potato black scurf. [Methods] R. solani JT18 (CK), R. solani JT18 and ordinary organic fertilizer (OF), R. solani JT18 and amino acid organic fertilizer (AA+OF) and R. solani JT18 and QHZ11 biological organic fertilizer (BOF11) were inoculated respectively into the sterilized soil. Using real-time fluorescent quantitative PCR (RT-qPCR) method to study the quantity changes of R. solani JT18, and law of quantity's increase and declining between the antagonistic antibacterial QHZ11 and R. solani JT18 under the different treatments in the rhizosphere and different parts of the plant during the whole growth period of potato. At the same time, we compared the disease index of black scurf of different treatments and the corresponding control effects.[Results] The results of RT-qPCR showed that with the progress of potato growth, the quantity of R. solani JT18 in potato rhizosphere, roots and stolons under each treatment increased to the peak in the tuber expansion period, and then decreased. The quantity of R. solani JT18 in each part was:CK>OF>AA+OF>BOF11, rhizosphere>root>stolon. The quantity of antagonistic antimicrobial QHZ11 showed the same trend as R. solani JT18, but its peak appeared in the tuber formation period, and the colonization quantity of QHZ11 was significantly higher than R. solani JT18 in the same part of the same period, even two orders of magnitude higher. It showed that the existence of QHZ11 occupied certain nutrient resources and niches, which severely inhibited the growth and reproduction of R. solani JT18. The results of the disease showed that the disease index of CK was the highest, another three treatments were significantly lower than CK in which BOF11 had the least disease incidence. The results of biocontrol were just opposite, which were BOF11>AA+OF>OF. It showed that ordinary organic fertilizer, amino acid organic fertilizer and bio-organic fertilizer could control potato black scurf to varying degrees, among which bio-organic fertilizer had the most significant effect. [Conclusion] After QHZ11 is made into bio-organic fertilizer and applied to the soil, it can effectively inhibit the survival and reproduction of pathogen of black scurf by competing for nutrition and niches in the rhizosphere and different parts of potato plant, thereby achieving significant biocontrol effect. It is of great significance to the application and promotion of bio-organic fertilizer of QHZ11, and lays a foundation to further research the biological control mechanism of QHZ11.

Abstract:[Background] Glycine soja has some excellent characteristics over the cultivated soybean, which is related to its unique endophytic bacteria and has become a research hotspot. [Objective] The endophytic bacteria of G. soja were isolated and identified. The strains with growth-promoting activity and stress-resistant potential were screened out. [Methods] The endophytic bacteria were isolated by tissue culture and streaking method. The strains were identified based on morphological, physiological, and biochemical characteristics and the 16S rRNA gene sequence-based phylogenetic analysis. The growth-promoting characteristics of the strains were analyzed by selective media or colorimetric method. Hydroponic experiment was carried out to analyze the effect of strain on the growth of rice seedlings. Salt stress and PEG-6000 simulated drought stress were used to explore the stress resistance of the strain. [Results] A strain YDX26 was isolated. According to the morphological, physiological and biochemical characteristics, and the results of phylogenetic analysis based on 16S rRNA gene sequence, the strain YDX26 was primarily identified as Pseudomonas sp. This strain had the phosphorus solubilization of 46.12 mg/L, the IAA activity of 19.97 μg/mL, and the ACC deaminase activity of 3.95 μmol/(mg·h). Moreover, it significantly increased the height, root length, aboveground dry weight, and underground dry weight of rice seedlings by 17.34%, 12.19%, 5.32%, and 10.70%, respectively. Compared with the control strain DX22, strain YDX26 showed improved salt and drought tolerance. [Conclusion] The endophytic bacterial strain YDX26 has better growth-promoting ability and salt and drought tolerance, and thus can be used as a new strain resource for agricultural production.

Abstract:[Background] Quinclorac (QNC) is a highly selective, hormonal, and low-toxic herbicide. It is mainly used to control barnyard grass in rice fields with a long duration. And the growth and development of subsequent crops are easily affected by QNC accumulated in the soil. In addition, the growth and development of animals will be affected by the residual QNC in the environment, as well as the community structure and the abundance of microorganisms also will be affect. [Objective] To isolate and screen a strain of degrading the herbicide QNC from the paddy soil, and determine its degradation-characteristics. [Methods] The strain was identifiedby morphological, physiological and biochemical tests, phospholipid fatty acid (PLFA) microbial identification, 16S rRNA gene sequence. The degradation characteristics of strains with single factor analysis was carried out. [Results] The QNC-degradation strain numbered 15^# was screened and identified as Achromobacter sp. The results of the research on the degradation characteristics show that the optimum conditions for strain 15^# were 30℃, pH 6.0, initial QNC concentration 100 mg/L, inoculation amount 7%, and added mass fraction 0.1% of yeast extract powder and nitrogen source are peptone. Under the conditions, the degradation rate of QNC could reach 43.0% after cultured 21 d. [Conclusion] A new strain was screened for microbial degradation of QNC and provided a theoretical basis for further research on this strain.

Abstract:[Background] Botrytis cinerea is one of the main pathogenic of grapes during postharvest, which seriously affects the storage period and quality of grapes and brings great losses to its industry. The use of antagonistic microorganisms to inhibit the growth of postharvest pathogens has gradually become an important method for the prevention and control of postharvest gray mold in grapes. [Objective] In order to provide new materials and research direction for the inhibition of Botrytis cinerea postharvest. Using the broad-spectrum and efficient antibacterial characteristics of entomopathogenic nematode symbiotic bacteria and screening high antagonistic effect on Botrytis cinerea from the symbiotic bacteria resources. [Methods] Antagonistic symbiotic bacteria were isolated and screened by plate confrontation culture method and mycelial growth rate method, and antagonistic symbiotic bacteria with highly effective, its 16S rRNA gene phylogeny analysis was carried out. The effect of antagonistic symbiotic bacteria on mycelial growth of Botrytis cinerea was studied by scanning electron microscope, and the control effect on Red Globe grape was verified by damage inoculation method. [Results] Nine strains had antagonistion were isolated from 14 bacteria, that one of symbiotic bacteria (ALL) was obtained through rescreening and retesting with significant antibacterial effect. According to phylogeny analysis, it clustered in the same branch with strain Xenorhabdus nematophila NC116 and 99.79% homology, which was identified to Xenorhabdus nematophila (Genbank accession number:MW488402). The strain caused the Botrytis cinerea hyphae to distort, shrink and collapse by scanning electron microscopy observation. The inhibition rate of the growth of Botrytis cinerea hyphae reached 44.5%, When the supernatant concentration was 1% in medium after fermentation (36 h). Compared with the control group, the fermentation supernatant of strain ALL had a better control effect on Botrytis cinerea, and the control effect was 63.50% after 3 days at room temperature. [Conclusion] In this study, we used entomopathogenic nematode symbiotic bacteria to inhibit Botrytis cinerea for the first time during grapes storage, and one of entomopathogenic nematode symbiotic bacteria was screened with high efficiency against Botrytis cinerea, and its supernatant had good inhibitory effect on Botrytis cinerea. The research provided a new biomaterial and related basis for bio-control of Botrytis cinerea during grapes storage.

Abstract:[Background] Many Methylobacterium can promote the growth of host plants, which is widely distributed. Screening methylobacterium strains with salt tolerance and growth promoting characteristics can provide basis for the development of microbial fertilizer, which can provide a basis for the development of microbial fertilizer. [Objective] Salt tolerant and plant growth-promoting bacteria were isolated from the saline soil of Wuerhe area in Xinjiang, and the culture medium were optimized after identification, the performance of growth-promoting was preliminarily studied. [Methods] The salt tolerant strains were screened by Ashby medium. The gene sequence analysis, physiological and biochemical determination were carried out on the strains. The effects on the growth of Arabidopsis thaliana were preliminarily studied by plate test. [Results] Moderate salt tolerant strains W-1 screened were identified as Methylobacterium sp. The best inorganic salt for the growth of strain was NaCl, and the optimum concentration was 1%-3%, and the maximum tolerance concentration was 7%. The best nitrogen source was organic nitrogen (acid hydrolyzed casein), with the highest yield of auxin (IAA) up to 33.53 mg/L, The dissolved phosphorus capacity was 28.71 mg/L. Inoculating Arabidopsis thaliana seedlings with the Methylobacterium sp. W-1, The contents of chlorophyll a and chlorophyll b of the Arabidopsis seedlings were higher than control group, the root structure of Arabidopsis thaliana was promoted significantly. [Conclusion] This study provided strain resources for the preparation of biofertilizer candidates.

Abstract:[Background] In recent years, the damage of potato scab disease has gradually increased, and it has occurred in all major producing areas across the country. At present, the lack of effective prevention and control methods has caused serious economic losses. Biological control is an effective way to prevent and control soil-borne diseases, and has gradually become a research hotspot. [Objective] Screening strains with high antagonistic effect on Streptomyces scabies will provide strain resources for the development of biocontrol agents and lay a theoretical foundation for the prevention and control of potato scab. [Methods] The isolated strains were preliminarily screened and re-screened by the plate confrontation growth method and the Oxford cup test method, and the strains were identified by morphological characteristics, physiological and biochemical characteristics, and 16S rRNA and gyrB sequence analysis results. The antifungal spectrum of the strain was determined by the plate confrontation method. [Results] A strain BKS104 with obvious antagonistic effect was obtained, with a antifungal diameter of 43 mm and a control effect of 85%. The colony is round, milky white, opaque, shiny surface, neat edges, rod-shaped bacteria, Gram-positive bacteria. Combined with the sequencing results of 16S rRNA and gyrB, it was identified as Bacillus velezensis, and it has inhibitory effect on 8 kinds of plant pathogenic fungi. [Conclusion] The strain BKS104 is B. velezensis, which can effectively inhibit the growth of Streptomyces scabies, with high safety and good biocontrol potential.

Abstract:[Background] The soil-borne heart rot is common in pineapple production. [Objective] This paper aims to enhance the cultivation and disease prevention of pineapple under continuous cropping. [Methods] Soil was collected from the orchards with continuous pineapple cropping for pot experiment. With three substrates (coir, peat soil, rapeseed cake), biocontrol strains (Bacillus subtilis HL2, Streptomyces HL3), and commercial organic fertilizer, different biological organic fertilizers were prepared and the effect of them on the plant growth and heart rot of pineapple was investigated. [Results] Compared with CK (chemical fertilizer only), the biological organic fertilizers promoted the growth of pineapple plants, significantly increased the fresh weight (leaf, stem, root), dry weight (leaf, stem, root), and longest leaf length, and reduced the incidence of heart rot. Among the biological organic fertilizers, KC (80% organic fertilizer + rapeseed cake + HL2) demonstrated the best control effect, followed by KY (80% organic fertilizer + coir + HL2), KN (80% organic fertilizer + peat soil + HL2), and LY (80% organic fertilizer + coir + HL3) with the control rate of 83.5%, respectively. However, YJ (organic fertilizer only) showed the poor control effect. Correlation analysis showed that the content of the soil pathogen (Phytophthora nicotianae) was negatively correlated with actinomycetes, organic matter, and pH (p<0.001) but positively correlated with soil available potassium content (p<0.05) and the incidence (p<0.01). [Conclusion] In a word, the biological organic fertilizers promoted the growth of pineapple plants and decreased the incidence of heart rot. These results can serve as a reference for the healthy development of pineapple industry.

Abstract:[Background] Cereal protein of raw material can provide nutrients such as nitrogen sources for the growth of microbial community, and then form a variety of metabolites during Chinese liquor fermentation. Cereal protein includes albumin, globulin, kafirin and gluten. However, the regulation of cereal protein on microbial diversity and metabolic diversity is still unclear. [Objective] This study aimed to reveal the key cereal protein that are significantly related to microbial diversity, and the effect of their regulation on microbial diversity and metabolic diversity. [Methods] The cereal protein was determined by Osborne's method; Identification of microbial diversity and metabolic diversity via HS-SPME-GC-MS and high-throughput sequencing during fermentation with 4 cultivars of sorghum. The key cereal protein was verified by simulated fermentation in vitro. [Results] The cereal protein of 4 sorghum was significant difference (ANOSIM:R=0.85, P=0.001); The bacterial diversity of sorghum S4 was significantly higher than others (P<0.05) at day 5 of fermentation with 4 sorghum; The metabolic diversity of sorghum S3 was significantly higher than others (P<0.05) at day 5 of fermentation with 4 sorghum. The contents of albumin and globulin were significantly correlated with the dominant bacterial diversity (R²=0.34, P<0.05; R²=0.58, P<0.05) and metabolic diversity (R²=0.58, P<0.05; R²=0.36, P<0.05) at day 5 of fermentation. Thus, they are defined as the key cereal protein; In vitro validation confirmed that the dominant bacterial diversity and metabolic diversity would increase with the increase of albumin and globulin content. When the albumin content is 3.0 g/L, the dominant bacteria diversity and metabolite diversity are 0.72 and 0.65, respectively; when the globulin content is 3.0 g/L, the dominant bacterial diversity and metabolite diversity are 0.66 and 0.81, respectively. [Conclusion] The study revealed the regulation of albumin and globulin in raw material on the diversity of bacteria and metabolites, and providing a new perspective for improving the controllability and quality of Chinese liquor fermentation.

Abstract:[Background] Daqu fungi provide starter and saccharifying agents for Baijiu fermentation process and fire cycle provides important flavor substances for Baijiu production, while the fungal community succession and flavor function in fire cycle remain unclear. [Objective] To explore the succession and flavor function of the fungal community in the fire cycle of medium-high temperature Daqu, and provide a theoretical support for optimizing the making process of Daqu and improving the quality of Baijiu. [Methods] The headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed to detect the flavor compounds, and internal transcribed spacer (ITS) amplicon sequencing was performed to analyze the fungal community structure. With the physical and chemical parameters of Daqu fire cycle, the redundancy analysis was conducted to explore fungal succession and flavor function of fire cycle during the production of Daqu. [Results] Some ester compounds (ethyl acetate, ethyl butyrate, ethyl hexanoate, methyl-alpha-galactopyranoside, and ethyl oleate), aromatic compounds (ethyl phenylacetate, 2,4-dimethylbenzaldehyde, benzyl alcohol, and phenethyl alcohol), acid compounds (acetic acid), alcohol compounds (3-octanol and furfuryl alcohol) had higher content in the fire cycle than in the surface and core of medium-high temperature Daqu. From the fourth stage, the fire cycle had the temperature higher than 40℃ and the reducing sugar content greater than 2%, and the Maillard reaction occurred to form the fire cycle. Pichia kudriavzevii and Saccharomycopsis fibuligera were the dominant fungi in the fire cycle, with the relative abundance over 95% at the 2-3 stage of Daqu production. At this time, the fungal diversity in the fire cycle was the lowest. [Conclusion] The succession of fungal community in the fire cycle of medium-high temperature Daqu was mainly affected by reducing sugar content and temperature. The fire cycle provided important ester compounds, aromatic compounds, acid compounds, alcohol compounds and other flavor substances for Baijiu production, and supplied the core yeast species for Baijiu fermentation, such as P. kudriavzevii and S. fibuligera. Fire cycle played an important role in the production of Baijiu. Our study further deepened the understanding of the fire cycle, and offered a theoretical basis for the adjustment of Daqu-making process and the improvement of Baijiu quality.

Abstract:[Background] Brucella can infect humans and animals by mouth, skin, mucous and respiratory tract. Mice are the most commonly used model animals in the study of Brucella. [Objective] The study aimed to establish the BALB/c mice model infected by Brucella abortus strain 2308 with different routes and doses, and to provide reference for mice infection experiments by Brucella. [Methods] The BALB/c mice were infected with 5 different doses of 10¹-10⁵ CFU by injection, mouth and eye droppings respectively. The serum samples were collected at different time points after infection in order to detect IgG, IgM and IgA antibodies. Combined with the results of spleen weight and bacteria content, we evaluated the effect of BALB/c mice model infected with Brucella by different routes. [Results] The results showed that 10 CFU was the minimum infection dose for injection, and 10⁵ CFU was the minimum infection dose for oral administration. The BALB/c mice could not be successfully infected with 5 different doses of 10¹-10⁵ CFU by eye droppings. At 10⁵ CFU infection dose, the average bacteria content per gram spleen of mice in oral and injection groups was 10^5.673 CFU/g and 10^5.009 CFU/g respectively, and there was no significant difference between them (P>0.05). However, the average weight of spleen was 0.310 g in the oral group, which was significantly higher than 0.165 g in the injection group (P<0.01). During the experimental period, the titers of IgG antibody increased continuously with the increase of infection time in injection and oral groups. Overall, the IgG peak value of oral group was significantly higher than that of injection group. The IgM change trend was coincide between the two groups. Two mice in oral group produced IgA antibody 28 days after infection, but IgA antibody was not detectable in injection group. [Conclusion] This study established the BALB/c mice model infected Brucella abortus strain 2308 by different routes.

Abstract:[Background] As an opportunistic pathogen, Trueperella pyogenes is frequently associated with mixed infections with porcine reproductive and respiratory syndrome virus, porcine circovirus, or Pasteurella, which can cause various non-specific suppurative infections. Some clinical symptoms are similar to those of Haemophilus parasuis infection. In this study, a bacterial pathogen showing β-hemolysis was isolated from the lung of an infected pig that died of respiratory symptoms in Jiangxi Province. [Objective] To investigate the species, biological characteristics, and genomic characteristics of the isolated pathogen. Our study aimed for better understanding of the pathogenesis of bacterial infection. [Methods] The morphology of the isolated bacteria was characterized by transmission electron microscopy and scanning electron microscopy. The pathogenicity, biological characteristics, and genomic characteristics of the bacteria were confirmed through animal experiments, drug sensitivity test, whole genome sequencing and bioinformatics analysis, respectively. [Results] Through morphology observation, identification of 16S rRNA gene, and phylogenetic analysis, it was confirmed that the isolated pathogen was Trueperella pyogenes and named JX18. Results of the drug sensitivity test showed that JX18 was resistant to clindamycin and lincomycin, but sensitive to other selected drugs. The results of animal experiments showed that typical symptoms of suppurative infection appeared in the abdomen of mice after the challenge of T. pyogenes JX18. All mice challenged with the highest dose died. Results of the whole-genome sequencing showed that JX18 carries important virulence genes, including plo, nanH, nanP, fimA, fimC and fimE. Moreover, these virulence genes have high homology with that of other T. pyogenes strains. Results suggested that genes involved in the carbohydrate transport and metabolism have the highest proportion in the genome of JX18. According to the VFDB and UniProtKB/Swiss-Prot databases, JX18 carries multiple histidine-kinase genes, response regulator genes, genes of the bicomponent regulatory system, and virulence genes related to adhesion, invasion, and secretion. [Conclusion] In this study, a high pathogenic pathogen, T. pyogenes JX18, was isolated in Jiangxi province and had been identified. Our study may enrich the pathogenic information of T. pyogenes, and provide the foundation for exploring strategies for the prevention and control of T. pyogenes infection.

Abstract:[Background] Compared with inactivated vaccines and attenuated vaccines, the superiority of Salmonella genetically engineered live attenuated vaccines has gradually emerged, and research has continued to deepen. [Objective] To explore the immunogenicity and biological safety of four gene-deleted strains of Salmonella enteritidis G9 strain:G9(ΔhilA), G9(ΔhilD), G9(ΔssrABhilA) and G9(ΔssrABhilAhilD).[Methods] Salmonella enteritidis strain G9 and gene deletion strains G9(ΔhilA), G9(ΔhilD), G9(ΔssrABhilA) and G9(ΔssrABhilAhilD) were inoculated with the optimal immunization doses to mice, and then used indirect ELISA and flow cytometry, MTT method, mouse challenge test and pouring plate method to evaluate the immunogenicity and safety of each deletion strain.[Results] G9(ΔhilD) induced the highest titer of serum IgG antibody, G9(ΔhilD) and G9(ΔssrABhilAhilD) produced the highest titer of intestinal mucosal IgA antibody, and 4 strains of deletion bacteria induced IL-4, IL-10, IFN-γ, TNF-β, MCP-1 cytokine capacity was not significantly different from that of the parent strain G9 (P>0.05), the ratio of CD4⁺/CD3⁺, CD8⁺/CD3⁺ T cells showed an upward trend, and G9(ΔssrABhilA) and G9(ΔssrABhilAhilD) were the highest; G9(ΔssrABhilAhilD) induced the highest proliferation index of splenic lymphocytes; after immunization of mice, the protection rate of the four deletion strains against G9 challenge was 80%-100%. The structure of the spleen and small intestine villi was relatively complete without obvious pathological changes. The protection rate against Salmonella typhimurium challenge is 50% to 80%; 12 days after inoculation, the colonizing strains in the liver, spleen and small intestine of mice could be basically eliminated. And it could be continuously and stably passaged for 30 generations in vitro.[Conclusion] G9(ΔhilA), G9(ΔhilD), G9(ΔssrABhilA) and G9(ΔssrABhilAhilD) had good immune effects and biological safety in mice, and they had the possibility of becoming genetically engineered live attenuated vaccines of Salmonella enteritidis.

Abstract:[Background] Studies about effects of epigenetic enzyme chemical inhibitors on metabolites of fungi mainly focus on new metabolites mining while content change of large number of known metabolites are less concerned. Metarhizium anisopliae is a common insecticidal fungus which can synthetize many known bioactive metabolites. Content variation of the metabolites can possibly affect the relationship between the fungus and the environment and its utilization potential.[Objective] To assess the effects of histone deacetylase and DNA methylase inhibitors on the safety and availability of metabolites of M. anisopliae. [Methods] Chemical inhibitors of epigenetic enzyme were added in medium of M. anisopliae. After a period of cultivation the metabolic changes were analyzed with high-performance liquid chromatography (HPLC) combined with high-resolution mass spectrometry (HRMS) and with some standards comparison. The effects of the inhibitors were evaluated by the bioactivities of the changed metabolites. [Results] Results of HPLC-HRMS showed that the content of 16 main metabolites of M. anisopliae changed significantly while the concentration of the inhibitors reached 500 μmol/L. The changed metabolites included destruxin A, A1, A2, B, B1, B2, E, E2, Ed, didesmethyldestruxin C, dihydrodestruxin A, desmethyldestruxin B, 12-hydroxyovalicin, subglutinol C, fungerin and ustilagic acid C. Sodium butyrate can increase 15 of the main metabolites production, and benzamide can increase 12 of the main metabolites production. Despite that SAHA can only increase 10 of the main metabolites production, some of the increased levels were much higher than the two formers. All the destruxins were decreased in the DNA methylase inhibitors treated M. anisopliae. [Conclusion] Chemical inhibitors of histone deacetylase can increase the contents of the main metabolites of M. anisopliae while inhibitors of DNA methylase can decrease all the destruxins in the fungus. Because of that all the main variated metabolites possess insecticidal, immunosuppressive, antibacterial, anti-cancer or other biological activities, the above inhibitors can strengthen or weaken the toxicity of the fungus against insects in the environment and increase or decrease metabolic utilization value of the fungus. Additionally, subglutinol C, fungerin and ustilagic acid C were identified for the first time from M. anisopliae.

Abstract:[Background] A fluffy fungal fruitbody (No. HMNWAFU-CF-HS002) was collected from the rotten stumps of Paulownia tomentosa in Shaanxi province, China. [Objective] Morphological description and molecular identification were carried out to determine its taxonomic status. [Methods] Macroscopic features were imaged, while microstructures were measured, counted, and drawn. Living culture was isolated and purified with PDA, and phylogenetic analysis of rDNA internal transcribed spacer (ITS) was performed with maximum likelihood (ML), maximum parsimony (MP), and bayesian inference (BI) methods. [Results] The morphological characteristics of HMNWAFU-CF-HS002 were highly similar to those of Punctularia atropurpurascens. Phylogenetic analysis showed that HMNWAFU-CF-HS002 nested into the P. atropurpurascens clade. [Conclusion] Based on the morphological evidences and phylogenetic results, HMNWAFU-CF-HS002 was identified as P. atropurpurascens, a new record species in China. P. tomentosa is a new record host species for P. atropurpurascens. So far, all the three species of Punctularia have been recorded in China.

Abstract:Swine gut-mammary gland-sIgA (secretory IgA) axis is an immune route involving pregnant sows, which, once being infected or vaccinated by a gastroenteric route with an enteric pathogen can confer immune protection to their offspring against such pathogen through IgA contained in their colostrum or milk. The dynamic model of the axis is composed of complicated processes (e.g., invasion of pathogen, antigen presentation, activation of lymphocytes, homing of lymphocytes into intestine or mammary gland, and antibody secretion), which may be influenced or regulated by various factors such as virulence of pathogen, stage of pregnancy, and immune state of sow. The study about the axis model evoked by infection of porcine epidemic diarrhea virus (PEDV) can be used to explain the immune protection acquired through infection of virulent virus, while the design of vaccine and vaccination protocol depending on the model has not been satisfactory. This review summarized the studies about PEDV infection and host immune response and analyzed the key factors influencing the axis. it is suggested that more attention should be paid to functions of inactivated PEDV vaccine and specific IgG antibody though the immune axis, which is the most efficient mechanism for PEDV prevention.

Abstract:Metagenome refers to the sum of genetic material of all the microorganisms in an environment. The technology of metagenomics can make the best use of microbial resources in the environment, which has attracted increasing attention of microbiological researchers at home and abroad. There is a large number of microorganisms in the oral cavity, and the available studies about the microorganisms causing oral diseases are mostly limited to bacterial culture method. However, some microorganisms are difficult or unable to be cultured. Metagenomics technology will break this limitation and help to explore more oral microbial resources. Recent studies based on metagenomic sequencing have mapped the oral ecosystem, and more and more experiments have proved the role of oral microbiome in oral diseases and even systemic diseases. At the same time, these studies pave a new way for the diagnosis and treatment based on human microbiome. This review demonstrates that metagenomics is a powerful tool for the study of microorganisms related to human oral diseases and systemic diseases and has a broad development prospect, and also discusses the limitations to be overcome in the application of metagenomics.

Abstract:The human intestinal flora can produce a variety of metabolites, or interact with human body to produce intestinal flora-host co-metabolites, which can impact the physiological functions of the major body systems. When the health conditions and intestinal flora change, the types and content of the metabolites will be affected accordingly, which indicate that the intestinal flora metabolites can be potential indicators for disease diagnosis. This article summarizes several common types of intestinal microbial metabolites, including carbohydrates, choline metabolites, lipids, amino acids and peptides, vitamins, bile acids, short-chain fatty acids, phenols, and benzoyl and phenyl derivatives. Furthermore, we expound their mechanisms of action in different diseases to highlight the correlations between intestinal flora, metabolites, and diseases, and to indicate that intestinal metabolites can be served as the new targets for the prevention, diagnosis, and treatment of these diseases.

Abstract:Bacterial translocation has been intensively studied for several decades. However, the Chinese translation of bacterial translocation is still inconsistent and unstandardized at present. To solve this problem and provide a theoretical basis for the proper translation, this paper clarified the research background, terminological definition, mechanism, and biological significance of bacterial translocation. We then systematically summarized the frequency of the two main translations in Chinese literature. Furthermore, basing on the original meaning and biological process, we discussed the corresponding translation of bacterial translocation. We finally adopted the more accurate and more recognized one for promoting the standardization in relevant research.

Abstract:In recent years, the application of arbuscular mycorrhizal fungi (AMF) in greenhouse vegetable production has shown that AMF inoculation during vegetable seedling breeding can produce mycorrhizal seedlings with good quality and strong resistance. Via various mycorrhizal effects, the application of AMF in vegetables production has proven that AMF can improve the nutrition and water supply of vegetables, enhance the tolerance of vegetables to environmental stress, increase the resistance of vegetable root diseases and nematodes, and improve the yield and product quality of vegetables. These functions of AMF are of importance in agriculture. Based on the beneficial effects of AMF on vegetables, this paper reviews the research progress of AMF in promoting vegetable growth, increasing vegetable yield and quality, alleviating its abiotic stress, controlling pathogens, and applying AMF in combination with pathogenic bacteria (or pesticides), so as to provide reference for the application of AMF in vegetable production in the future.

Abstract:Anthracnose is a major plant disease prevalent around the globe, which causes quality deterioration and serious yield losses of soybean and mungbean. This paper summarized the occurrence, pathogen species, and characteristics of soybean anthracnose at home and abroad, aiming to provide a theoretical basis for understanding the epidemiology and scientific control of this disease.

Abstract:The disturbance of gut microbiota contributes to pathological bone loss in the host, as the metabolites of it diffuse from the gut to the systemic circulation to regulate bone metabolism. Among the metabolites of gut bacteria, short-chain fatty acids (SCFAs) attract the most attention. Recent studies have shown that SCFAs play an important part in the prevention and treatment of bone metabolism-related diseases. This review focused on the role of SCFAs in the skeletal system, the mechanism of regulating cells in bone tissue, and the functions in the prevention and treatment of osteoporosis, and summarized the future research directions.

Abstract:Keratin is the main component of feathers and many agricultural waste. It is difficult to be used because it has a large number of stable cross-linked disulfide bonds, which can resist degradation of common proteases and chemical catalysts. These waste resources are accumulate massirely and cause serious environmental pollution. Microbial keratinase can efficiently convert keratin wastes into the reusable products which will bring economic value, and make environment sustainable. This article mainly reviews the biochemical characteristics, the basic structure, the expression characteristics, and the application of microbial keratinases. Finally, the future research topics of the microbial keratinase were proposed and prospected.

Abstract:Pit mud is a characteristic fermentation carrier of Luzhou flavor liquor, which contains many kinds of flavor producing microorganisms that have an important influence on the style and quality of Luzhou flavor liquor. This study summarizes and compares the microbial activities of cellar mud of different ages, different flavor liquor producing areas and cellar mud microorganisms of different quality, and then analyzes the function of these microbes in pit mud. The purpose of this study is to provide a new thought for the research of cellar mud microorganisms, for improving the quality and flavor composition of Luzhou flavor liquor. It is helpful to promote the research of microbe in pit mud, and deepen the knowledge of pit mud.

Abstract:Agrobacterium tumefaciens-mediated transformation (ATMT) has many advantages such as high transformation efficiency, genetic stability, and a wide range of applications. It has become a powerful method in the study of fungal genetics. It plays a huge role in fungal disease research and heterologous protein expression research. This article summarizes the research progress, technical advantages and disadvantages, transformation mechanism, experimental methods and application status of ATMT technology in fungi studying. This review also focuses on the influencing factors of ATMT transformation efficiency and discusses the optimization methods. The application prospects of genome editing and other aspects are expected to provide references for future fungal genetic transformation research.

Abstract:With the massive and irregular use of antibiotics, the antibiotic resistance of bacteria continues to increase, leading to the emergence of drug-resistant and multi-drug resistant bacteria, which seriously threaten human health. Therefore, the application of statistical methods to summarize and multi-analyze the research on antibiotic resistance will help to better understand the prevalence and distribution of antibiotic resistance bacteria worldwide, clarify the common problems of the laws and mechanisms of the formation of drug resistance, and provide effective and scientific guidance for prevention and control the breeding and transmission of bacterial resistance. Meta-analysis is a statistical method that comprehensively analyzes multiple studies in the same research field. It has been widely used in the study of bacterial resistance. In this comprehensive review, briefly describes the origin and basic process of Meta-analysis. The bibliometrics was used to systematically and comprehensively analyze the application of Meta-analysis in the study of bacterial antibiotic resistance from 2000 to 2020. Then, we summarized and explained the successful cases and conclusions of Meta-analysis in the field of bacterial resistance. Furthermore, the future research about Meta-analysis in the field of bacterial antibiotic resistance was prospected, for the view of promote the application of this method in the study of bacterial resistance, and provide a reliable tool for the systematic interpretation and effective control of bacterial resistance.

Abstract:Type I polyketide synthases (PKS) play an important role in catalyzing the biosynthesis of polyketides, which is widely used in medicine and other fields. According to different acyltransferase (AT) domains, type I PKS can be divided into cis-Acyltransferase (cis-AT) PKS and trans-Acyltransferase (trans-AT) PKS, the former has been studied more thoroughly at present, and the related research of the latter has become a hot spot. In this paper, the connections and differences between cis-AT PKS and trans-AT PKS, as well as engineering progresses, related applications and currently existing problems are reviewed, to provide a reference for understanding the role of cis-AT PKS and trans-AT PKS in the biosynthesis of polyketides.

Abstract:Ferroptosis is a new type of programmed cell death, in which elevated level of intracellular iron results in accumulation of lipid peroxides to a lethal level. At present, the functions and regulatory mechanisms of ferroptosis have been widely and extensively investigated in animal (including human) cells, but have just started and in a rather primary stage in fungal cells. In this review article, we aim to discuss the reported biological functions of the fungal orthologs to the regulatory factors involved in ferroptosis, including iron homeostasis, anti-oxidant systems of membrane lipids, and enzyme-catalyzed lipid peroxidation. Overall we infer that ferroptosis may also exist in fungi and be involved in fungal pathogenicity, therefore ferroptosis pathway would potentially be a novel target for prevention and management of fungal diseases.

Abstract:Biogenic amines (BAs), the potential health threats in fermented food and alcoholic beverage, bring about allergic reactions such as dyspnea, vomiting, and fever in the case of excessive intake. BAs-degrading enzymes, including amine oxidase, amine dehydrogenase, and multicopper oxidase, oxidize BAs to aldehydes. This review described the catalytic mechanism, substrate specificity, enzymatic properties, and applications of the three BAs-degrading enzymes and their capabilities of degrading BAs. The heterologous expression and molecular modification of them were also summarized. Furthermore, research trends of such enzymes in gene mining, molecular modification, and expression were summed up. The paper is expected to provide a reference for studying and developing strategies for degrading BAs in food with enzymes.

Abstract:Traditional fermented food is a system composed of a great variety of naturally inoculated microorganisms. Understanding the mechanism of microbial spontaneous construction is the foremost to unveil and control fermentation process. Although a large amount of sequencing data is produced to determine the microbial diversity and function, the mechanism of microbial spontaneous construction is still unclear. Here, we build on the perspective that microbial communities are fundamentally distributed metabolic systems, and are driven by trophic interactions. This review expounds the concept, mechanism and research methods of trophic interaction, and summarizes the research advances and future development of trophic interactions of microbial community in traditional fermented foods. The spontaneous construction of microbial community controlled by trophic interactions is helpful to targeting control microorganisms, improve the production efficiency and quality of traditional fermented foods.

Abstract:Animal Husbandry Microbiology is a course with high applicability. The traditional teaching mode that students follow teachers' experimental demonstration cannot meet the needs of cultivating innovative talents in Animal Husbandry. To improve students' ability of using microbiological knowledge to analyze and solve practical problems in animal production, we gradually completed a set of teaching mode combining theoretical course, basic operation skills and exploratory trial after five years of exploration aiming at Animal Husbandry Microbiological Experiment. This mode stimulated students' creativity and improved their research ability.

Abstract:In response to the appeal of the Ministry of Education about "golden curriculum construction", we took "student-centered" and "competence development" as the fundamental goal and task of the teaching reform. Our reform on teaching of Microbiology introduced modern education methods and adopted "online and offline blended" teaching mode. Online mode includes:(1) Providing all resources related to course teaching via Superstar Fanya network teaching platform with resources such as basic resources, auxiliary resources and development resources for students to study outside class; chapter teaching design consisting of self-study outline, famous teacher MOOCs, teaching interaction and homework exercises for students' self-study before class, interaction in class and review after class; stage questionnaire and suggestions for teaching evaluation and reflection. (2) Achieving the real-time interactive communication between teacher and students in and out of class via the "Learning Link" mobile app, including task arrangement, learning assessment, question and answer, teaching interaction and course feedback, etc. Offline mode includes:Taking class teaching as the carrier, based on students' online learning situation and teaching design, we took class teaching as the carrier to adopt the following methods:classified teaching for different types of knowledge, and a variety of interactive teaching methods. By doing so we consolidate the outcome of self-teaching, strengthen the key points, analyze the difficult points, then consolidate the foundation and develop students' capability at the same time. The results showed that all students recognized the methods and effects of the teaching reform. They felt that the goal of teaching reform is clear, the emphasis is prominent and the methods are optimized. The adoption of the teaching reform can inspire thinking, stimulate interest, effectively improve class participation, enhance subjective initiative, and improve their competence comprehensively.

Abstract:Microbiological Experiment, which is a compulsory course for biological majors, play very important roles in the cultivation and improvement of basic operation skills and innovation ability of students. In order to solve the problems in the traditional teaching model, a teaching reform based on the characteristics of micro-video of being short, fast and refined is performed. Three kinds of teaching resources are prepared, including basic operation micro-video, courseware micro-video and student experiment micro-video. By combing with other teaching and evaluation methods, the micro-video resources are effective and successfully applied in experimental teaching. Through the teaching model mentioned above, students' interests in learning are aroused, which improved their practical innovation ability and the microbiological experiment teaching quality.

Abstract:Online and offline blended teaching had become a new teaching mode adopted by many college course under the normalized epidemic prevention and control. Combining the advantages of LBL teaching and MOOC teaching, the course team re-constructed the online teaching process of Fermentation Engineering course with student as the center, and a series of reform and exploration were carried out on the teaching objectives, teaching requirements, teaching chapters, teaching assessment, teaching methods and so on. Meanwhile, the course team tried to turn the online flipped classroom and the ideological and political education integration into the classroom teaching mode, the students' enthusiasm for autonomous learning had been improved, and it also promoted and improved the teaching and learning effect of course teaching.

Abstract:Veterinary Microbiology is a basic course of veterinary medicine, and experimental course is an important part of this course, which is of great significance to the course objectives and the follow-up learning. To address the main pain points in the experiment teaching of Veterinary Microbiology and improve the teaching level for minority students, we randomly assigned 405 ethnic students into the experimental group (reformed teaching mode) and the control group (traditional teaching mode) by reasonably arranging experimental content and adopting the competition-mode examination. The students' test results and questionnaires were compared between the two groups. Compared with those in the control group, the test score, experimental operation ability, innovation ability, data processing ability, and problem analysis ability were significantly improved in the experimental group, which indicated that the revolution and innovation have achieved good teaching effect.

Abstract:[Background] In gene targeted therapy and gene engineering drug development with adeno-associated virus (AAV) as the delivery vector, the challenges of the large-scale preparation of highly purified recombinant AAV (rAAV) should be solved. [Objective] The goal of this study was to obtain highly purified rAAV particles by purification of plasmids and rAAV cell culture medium. [Methods] HiPrep^TM10 Sepharose 6FF and HiTrap PlasmidSelect Xtra gel chromatography columns were used to purify three rAAV plasmids. The study sought to obtain super helical DNA plasmids and optimize the culture of AAV-293 cells in the assembly process. After successful assembly, the virus extract was purified using HiLoad^TM10Q and HiLoad^TM10SP cation exchange columns. HT1080 cells were infected with purified and concentrated rAAV. Flow cytometry was used to enumerate the fluorescent cells to detect the number of live virus and calculate the titer of live virus after concentration. [Results] After HiPrep and HiTrap chromatography columns purification, many copies of highly purified super helical plasmid DNA were obtained. After virus assembly, many highly purified rAAV particles were obtained by cation exchange chromatography. The genome titer of rAAV (TCID₅₀/mL) reached (2.46±0.37)×10¹²(multiplicity of infection of 1.0×10⁴). [Conclusion] A high titer of pure rAAV was prepared by a series of assembly refinements and purification.