Abstract:[Background] Quinoline, a typical nitrogen-containing heterocyclic pollutant in coking wastewater, is teratogenic, carcinogenic, and mutagenic, posing a threat to the environment. Microbial technology is environmentally friendly and efficient in the treatment of water polluted by quinoline. [Objective] To screen an efficient quinoline-degrading microbial consortium for the industrial treatment of quinoline-containing wastewater.[Methods] An efficient consortium was screened from the sludge of a coking wastewater plant by incremental stepwise domestication. The morphology was observed and the enzyme activity and substrate spectrum were tested. Then, the pH, temperature, rotational speed, loading volume, inoculum volume, and concentration of added carbon and nitrogen sources for the culture of the microbial consortium were optimized by single factor test. [Results] A consortium which can degrade 1 500 mg/L quinoline in 30 h was isolated. It can degrade a variety of nitrogen-containing heterocyclic compounds. The results of response surface methodology showed that the highest degradation rate of 66% was achieved at pH, temperature, and rotational speed of 6.8, 30 ℃, and 200 r/min, respectively. The degradation kinetic analysis revealed that the maximum specific degradation rate of 60.0 mg/(L·h) was achieved when the quinoline concentration was 1 154 mg/L. [Conclusion] The microbial consortium has a high quinolone-degrading capacity and a broad spectrum of substrates. The findings lay a basis for the industrial treatment of quinoline-containing wastewater by microorganisms.

Abstract:[Background] Petroleum is known as liquid gold. While creating a great social value, the utilization of petroleum for industrial production causes serious pollution to the environment. Microbial remediation is one of the effective approaches to control oil pollution, which has the advantages of low cost, high efficiency, and no secondary pollution. [Objective] To isolate and study the degradation characteristics and microbial remediation potential of highly efficient n-tetracosane-degrading strain from the oil-contaminated soil. [Methods] The strain was identified by morphological observation and 16S rRNA gene sequencing. Gas chromatography was employed to examine the n-tetracosane degradation effect of the strain. Further, we employed gas chromatography-mass spectrometry (GC-MS) to identify the degradation intermediates for predicting the potential metabolic pathway. [Results] Strain C24MT1 was identified as Acinetobacter sp., which was highly capable of degrading n-tetracosane. The optimum degradation conditions of the strain were 30 °C, pH 9.0, and salinity of 2 g/L, under which the degradation rate of 9 g/L n-tetracosane was 86.63%. The strain grew well (OD₆₀₀=0.39) in strong alkaline environment (pH 11) and maintained high alkane degradation rate (75.38%), demonstrating strong tolerance to extreme environment. According to the degradation intermediates, we predicted that the metabolic pathways of n-tetracosane in the strain might include terminal oxidation and subterminal oxidation. [Conclusion] Acinetobacter sp. C24MT1 had excellent environmental adaptability and alkane-degrading ability, demonstrating great application prospects in the development of microbial inoculants and the remediation of petroleum-contaminated soil. This study provides excellent bacterial resources for the remediation of soil contaminated by high-concentration petroleum in saline-alkali areas and enriches the bacterial resource for the biodegradation of petroleum hydrocarbons.

Abstract:[Background] Petrochemical wastewater contains nitrogen and has high salt content, which inhibits microbial metabolism and makes it difficult for common denitrifying microorganisms to effectively remove nitrogen. [Objective] To screen out and characterize the strains capable of efficiently removing nitrogen under high salt conditions. [Methods] A strain of salt-tolerant denitrifying bacterium was screened out and identified based on the physiological and biochemical properties and 16S rRNA gene sequence. The growth conditions of the strain were optimized and the denitrification capacity was measured. The products of the strain under high salt conditions were analyzed qualitatively and quantitatively. [Results] The strain YA16-1 was identified as Brevibacterium epidermidis and had the ability of denitrifying nitrate-nitrogen. It showed the nitrate-nitrogen removal rates of 97% in 18 h at 3% salinity and 55 mg/L initial nitrogen and 100% in 24 h at 250 mg/L initial nitrate-nitrogen. The optimum growth conditions for this strain were 2% NaCl, corn cob meal as the carbon source, yeast powder as the nitrogen source, pH 6.0, and 30 ℃. The strain grew well in media with salinity ranging from 2% to 15%. At 15% salinity, the strain maintained osmotic equilibrium by producing ectoine with the maximum titer of 0.89 mg/mL. [Conclusion] YA16-1 has good salt tolerance and denitrifying ability, demonstrating the potential of being applied in the treatment of high-salt wastewater and the production of ectoine.

Abstract:[Background] Caused by the abuse of antibiotics, the rapid emergence of resistant bacteria is occurring worldwide. For Bifidobacterium, the probiotic property has been emphasized, while there is a paucity of research on the antibiotic resistance. [Objective] To detect the antibiotic resistance of Bifidobacterium pseudocatenulatum isolated from the feces of mothers and infants and to explore the source of resistant strains in infant gut. [Methods] The resistance of 48 strains of B. pseudocatenulatum isolated from the feces of mothers and infants to 14 antibiotics was determined by the minimum inhibitory concentration method, and the resistance of strains isolated from different families was compared. [Results] All the 48 strains were resistant to tetracycline, chloramphenicol, neomycin, and ciprofloxacin, and 98%, 80%, 78%, 63%, 59%, 43%, 16%, 14%, 6%, and 2% of the strains were resistant to kanamycin, rifamycin, clindamycin, trimethoprim, erythromycin, gentamicin, streptomycin, vancomycin, ampicillin, and linezolid, respectively. There were no significant differences in antibiotic resistance between the isolates from mothers and infants, and isolates from the same family had similar antibiotic-resistant phenotypes. [Conclusion] The B. pseudocatenulatum isolated from feces of mothers and infants were resistant to a variety of antibiotics. The resistant strains in infant gut may be vertically transmitted from the mother's gut.

Abstract:[Background] In recent years, F-specific RNA bacteriophages have been recognized as indicators of human norovirus contamination in aquatic environments. Recently, using Escherichia coli ATCC700891^T as host, our group isolated an F-specific RNA bacteriophage YM1 from human stool sample. This bacteriophage has the closest relationship to E. coli bacteriophage MS2. The hosts of MS2 are usually the male E. coli containing pili. [Objective] To explore the interaction of F-specific RNA bacteriophage with its host and norovirus living in the intestine, this study aimed to screen out the intestinal hosts of YM1. [Methods] Selective medium was used to screen out the E. coli strains in YM1-positive stool sample, and YM1 infection was verified. In addition, the 16S rRNA gene amplicon sequencing was employed to analyze the differences of bacterial community in stool samples before and after YM1 inoculation, and the potential intestinal hosts of YM1 in the YM1-postive stool sample were analyzed. [Results] A total of 351 E. coli strains were isolated from YM1-positive stool sample. However, YM1 infection results showed that none of them were the hosts of YM1 bacteriophage. The 16S rRNA gene amplicon sequencing showed that the relative abundance of Enterobacter sp. (OTU144) and Enterobacter sp. (OTU11) in stool samples were significantly decreased after being infected with YM1, which indicated that these two kinds of bacteria might be the potential hosts of YM1. [Conclusion] YM1 targets to certain host in an extremely specific manner. E. coli is not the intestinal host of YM1 in stool sample. At the same time, two potential hosts of YM1 have been identified, which provided directions and references for the isolation and screening of the intestinal hosts of YM1.

Abstract:[Background] The tetramic acid derivatives, nocamycins and tirandamycins, possess C-10 ketone groups, the formation of which is catalyzed by two different enzymes: a short-chain dehydrogenase NcmD and a FAD-dependent dehydrogenase TrdL, respectively. In the biosynthetic pathway of nocamycins, whether the FAD-dependent oxidase NcmL can complement the function of NcmD remains unknown. Additionally, whether TrdL can catalyze the conversion of C-10 hydroxyl group to C-10 ketone group in nocamycins is also unknown. [Objective] To characterize the catalytic roles of NcmL and TrdL in the formation of C-10 ketone groups in nocamycins by using in vitro enzymatic assays. [Methods] The trdL and ncmL genes were respectively cloned into the vector pET-28a(+), and the recombinant vectors were then overexpressed in Escherichia coli BL21. TrdL and NcmL were purified and then used for the in vitro enzymatic assays. Nocamycins F and II were used as substrates and the products generated under the catalysis of NcmL and TrdL were determined by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometer (LC-MS). [Results] NcmL did not catalyze the dehydrogenation occurred on C-10 hydroxyl group. TrdL catalyzed the hydroxyl dehydrogenation at C-10 position in nocamycins II and F, leading to the generation of nocamycins I and G, respectively. [Conclusion] In vitro biochemical assays revealed that NcmL is not involved in formation of C-10 ketone group of nocamycins. TrdL shows a broad substrate spectrum and can catalyze the formation of C-10 ketone group in nocamycins.

Abstract:[Background] With the rapid development of metabolic engineering and synthetic biology, carbon dioxide fixation by biological methods through metabolic modification of heterotrophic microorganisms has become a new trend. There are a large number of carbon fixation enzymes in biological metabolic pathways, which are yet to be explored and applied, and there is a lack of comparison among the carbon fixation efficiencies of different enzymes. [Objective] To evaluate the carbon fixation function and efficiency in vitro and in vivo. [Methods] Three carbon fixation enzymes, namely, ribulose 1,5-diphosphate carboxylation oxygenase (RuBisCo), phosphoenolpyruvate carboxykinase (PCK), and acetyl coenzyme A carboxylase (ACC), were heterologously expressed in Escherichia coli and then purified. The enzymatic activities of the pure enzymes were determined, and a cell-free catalytic assay-liquid mass spectrometry method was established to evaluate the carbon fixation capacity of the enzymes. Metabolic indicators were examined under anaerobic fermentation conditions and the differences between Bacillus licheniformis overexpressing carbon fixation enzymes compared to the original bacteria were compared. [Results] All three enzymes achieved soluble expression with specific enzyme activities of 66.43, 1.16, and 12.52 U/mg for pure enzymes, respectively. RuBisCo and ACC exhibited stronger carbon fixation efficiency in cell-free catalytic assays. The conversion of lactic acid, the main product of anaerobic fermentation, was increased from 48.6% to 58.1% and 59.7%, respectively, in B. licheniformis with the two expressed recombinant enzymes. [Conclusion] The efficiency of carbon fixation enzymes can be evaluated by in vitro and in vivo binding. This study may provide references for rational and precise application of carbon fixation enzymes in microbial genetic modification.

Abstract:[Background] Endophytic fungi of pine trees can affect the growth and spread of Dendroctonus valens and its associated fungi, thus further influencing the invasion of D. valens. [Objective] To investigate the diversity of endophytic fungi in the hosts of D. valens in Chifeng, Inner Mongolia in northern China, and to screen strains against its associated fungi for the control of this destructive forest pest. [Methods] The endophytic fungi in the hosts Pinus tabuliformis and Pinus sylvestris var. mongolica and potential host Larix gmelinii were explored by tissue isolation, morphological identification, and ITS sequence analysis, and the antagonistic strains were screened with the plate confrontation method. [Results] The endophytic fungi in 19 genera, 18 families, 10 orders, 6 classes, and 2 phyla were identified from the three pine species. L. gmelinai topped the three species in the number of isolated strains (39 strains of 12 species in 9 genera), with fungal detection rate of 43.33%, followed by P. tabuliformis (30 strains of 8 species in 7 genera), with fungal detection rate of 33.33%, and coming in the third was P. sylvestris var. mongolica (29 strains of 13 species in 10 genera), with fungal detection rate of 32.22%. The three pine species had no common strains but had the common genera of Penicillium and Talaromyces. Penicillium dominated the fungi in all three pine species. The results of plate confrontation indicated that more than 90% of the endophytic fungi showed stable confrontation against the associated fungi, and the inhibition rate ranged from 50% to 86%. Particularly, the associated fungi-inhibiting rate of Phialocephala sp. and Pochonia bulbillosa stood at 93.7%. [Conclusion] The endophytic fungi in the bast of pine trees have high potential for biocontrol, and Phialocephala sp. and P. bulbillosa have satisfactory inhibitory effect on the concomitant fungi of D. valens and can be used for controlling D. valens.

Abstract:[Background] Exploiting biomethane resources is an effective way to alleviate the shortage of fossil fuel supply nowadays. At the same time, the methods of lignocellulosic biomass pretreatment and methane production need to be innovated for sustainable development. The co-cultivation of anaerobic fungi and methanogens enables dual pretreatment of lignocellulosic biomass and methane production by rhizoid invasion and fiber-degrading enzymes. However, only one culture of anaerobic fungi isolated from camel gut has been reported in the world. [Objective] To isolate and identify the novel co-culture of anaerobic fungus and methanogen from the rumen contents of Xinjiang Bactrian camels, and investigate its application potential in degrading lignocellulosic biomass and producing biomethane. [Methods] The co-culture of anaerobic fungus and methanogen was isolated by Hungate rolling-tube technique from camel gastrointestinal tract and then identified based on the morphological and molecular characteristics. Further, the biomethane production, degradation efficiency, and primary metabolites of the co-culure were determined by anaerobic fermentation with five substrates (rice straw, reed, Broussonetia papyrifera leaves, alfalfa stalk, and Melilotus officinalis). [Results] The co-culture CR1 of anaerobic fungus and methanogen was composed of Oontomyces sp. CR1 and Methanobrevibacter sp. CR1, which had high xylanase activity (21.64 IU/mL) and biomethane production (143.39 mL/g-DM) when degrading rice straw. Furthermore, CR1 had better methane production property than the anaerobic fungal co-cultures isolated from other animals. [Conclusion] The co-culture CR1 of anaerobic fungus and methanogen is a novel degrading strain with high efficiency, which has a promising application prospect in the production of biomethane from lignocellulosic biomass.

Abstract:[Background] Plant growth-promoting rhizobacteria (PGPR) has great potential in improving plant resistance and regulating soil nutrient status. [Objective] To provide efficient microbial resources for the development and utilization of microbial fertilizer, we isolated and screened out the strains with strong growth-promoting properties from the rhizosphere soil of tobacco. [Methods] The culturable bacteria in the rhizosphere soil of tobacco were isolated by the dilution-plate coating method. The strains with strong phosphorus-solubilizing activity were screened by PVK medium, and the phosphorus-solubilizing activity of each strain was determined by molybdenum-antimony resistance colorimetry. Salkowski’s colorimetric solution was used to determine the production of indole acetic acid (IAA). With the phosphorus-solubilizing amount and IAA yield as indicators, we optimized the fermentation conditions by single factor tests to obtain the optimal fermentation scheme for phosphorus solubilization and IAA production. The growth-promoting activity of the strain was verified by seed germination and seedling growth experiments. The strain was identified based on the morphological, physiological, and biochemical characteristics and 16S rRNA gene sequence. [Results] A total of 127 strains were isolated from the rhizosphere soil of tobacco. Ten of the strains had the ability to solubilize inorganic phosphorus, among which SH-1464 had the highest phosphorus-solubilizing activity with a diameter of 16.11 mm and an amount of 119.22 mg/L. Strain SH-1464 had strong IAA production of 39.88 μg/mL. The optimal fermentation conditions of SH-1464 for solubilizing phosphorus was 10 g/L glucose as the carbon source, 0.5 g/L peptone as the nitrogen source, 2.5 g/L Ca₃(PO₄)₂ as the inorganic phosphorus source, initial pH 7.5, temperature of 30 ℃, and rotation speed of 200 r/min. The optimum conditions of strain SH-1464 for producing IAA were 10 g/L maltose, 5 g/L yeast powder, 10 g/L NH₄NO₃, 2.5 g/L KCl, 0.1 g/L l-tryptophan, pH 6.5, 30 ℃, and 180 r/min. The phosphorus-solubilizing amount and IAA yield of the strain were compared before and after optimization. After optimization, the phosphorus-solubilizing amount and IAA yield of the strain was 225.9 mg/L and 75.3 μg/mL, which increased by 84.5% and 88.8%, respectively, compared with those before optimization. The inoculation of SH-1464 increased the germination rate of tomato seeds by 84.5%, plant height by 55.1%, stem circumference by 32.5%, root length by 16.4%, root weight by 149%, aboveground part fresh weight by 172.2%, and aboveground part dry weight by 203.6%. Strain SH-1464 was identified as Bacillus paramycoides (GenBank accession number: ON417365, deposit number: CCTCCM 2022924). In addition, the strain had the abilities of producing protease and cellulase, fixing nitrogen, and secreting siderophore. [Conclusion] Strain SH-1464 had the abilities of solubilizing inorganic phosphorus, fixing nitrogen, and producing IAA, protease, cellulase, and siderophore. It significantly improved the germination rate of tomato seeds and the seedling agronomic traits such as plant height, stem circumference, root length, root weight, and fresh and dry weight of aboveground part. This strain has a wide application prospect in the development and utilization of microbial agents.

Abstract:[Background] The problem of soil-borne diseases caused by successive cultivation of strawberries has become more and more prominent, and fumigants have been widely used for soil disinfection because of their remarkable effect. However, different fumigants have different effects on soil pathogenic organisms, and at the same time, they have different effects on non-target organisms and soil properties. [Objective] To explore the effects of different fumigants on soil nutrients, soil bacteria, and fungal diversity, thereby providing a scientific basis for the reasonable selection of fumigants. [Methods] Continuous cropping soil was used as material and treated with five treatments including control, soil fumigation using calcium cyanamide, soil fumigation using calcium oxide, soil fumigation using dazomet, and soil fumigation using metam-sodium, to measure soil nutrient content after fumigation. PacBio sequencing platform was used to analyze the microbial diversity of soil. [Results] Both calcium cyanamide and metam-sodium treatments increased the content of alkali-hydrolyzable nitrogen and decreased the content of organic matter, available phosphorus, and available potassium. Each nutrient content in the soil of dazomet treatment increased, while the content of alkali-hydrolyzable nitrogen, available phosphorus, and available potassium in calcium oxide treatment decreased except the content of organic matter. In addition, the pH of dazomet, calcium oxide, and metam-sodium treatments decreased significantly. A total of 1 164 bacterial OTUs and 444 fungal OTUs were obtained from five soil samples of strawberry continuous cropping. Analysis of bacterial diversity and richness showed that four fumigant treatments increased the richness of the soil bacterial community, and calcium cyanamide, calcium oxide, and metam-sodium treatments increased the diversity of soil bacterial colonies. As compared with the control, the richness of fungal colonies treated with four fumigants was lower, and the diversity of fungal colonies in calcium oxide and dazomet treatments was higher while that in calcium cyanamide and metam-sodium treatments was lower, but the difference was not significant. In the analysis of species composition, from the phylum level, the dominant bacterial phyla were Proteobacteria and Gemmatimonadetes. As compared with control, the relative abundance of Proteobacteria in calcium cyanamide, calcium oxide, and dazomet treatments increased, while that in metam-sodium treatments decreased. All four treatments reduced the relative abundance of Gemmatimonadetes. The four soil fumigation treatments increased the relative abundance of Planctomycetota and Verrucomicrobia in other phyla. The analysis of dominant bacterial communities showed that soil fumigation reduced the relative abundance of bacteria such as Gemmatimonas, Luteimonas, and Mesorhizobium, but increased that of Chitinophaga and Ochrobactrum. The dominant fungus phylum was Ascomycota, and the relative abundance of Ascomycota was increased by calcium cyanamide, calcium oxide, dazomet, and metam-sodium treatments. Cladosporium and Fusarium causing soil-borne diseases in strawberry roots were detected, and the relative abundance of Cladosporium and Fusarium decreased after the fumigant treatment, among which Cladosporium decreased by 1.35%, 1.11%, 0.90%, and 1.31%, and Fusarium decreased by 0.71%, 0.85%, 0.19%, and 0.65% in calcium cyanamide, calcium oxide, dazomet, and metam-sodium treatments, respectively. All four soil fumigants increased the relative abundance of Chaetomium, a beneficial fungus. [Conclusion] Comprehensive analysis shows that fumigant treatment of continuous cropping soil changes the microbial community composition, and reduces or kills most pathogenic bacteria in the soil, thus playing an effective role in preventing and controlling soil-borne diseases of strawberries. However, it cannot kill all pathogens and affect beneficial bacteria and soil properties to different degrees. Therefore, it is very important to supplement beneficial microorganisms after treatment. According to the killing effect of pathogenic bacteria, calcium cyanamide and metam-sodium treatments are superior to other treatments and can be used as fumigants for soil application in turn. Under this experimental condition, dazomet is a weak treatment agent.

Abstract:[Background] In view of the serious soil borne diseases and deteriorative soil physicochemical properties in protected cultivation of watermelon, we explored the effect of microbial agent on rhizosphere microbial community and soil nutrients of watermelon. [Objective] To study the effect of different treatments of Aspergillus niger agent on rhizosphere bacterial diversity and community structure, as well as soil physicochemical properties of watermelon. [Methods] Through high-throughput sequencing, we analyzed the effect of A. niger agent inoculation alone (Y), amino oligosaccharin water aqua (root irrigation) alone (A) or the combination of the two treatments (YA), on the rhizosphere soil bacterial diversity and community structure of watermelon. Analytical chemistry methods were used to detect the soil physicochemical properties and elucidate the main driving factors of their dynamic changes. [Results] The bacterial α diversity indexes of Chao 1, ACE and Shannon indices increased in Y, A, and YA treatments compared with those in the control. The dominant bacterial phyla in the rhizosphere soil of watermelon consisted of Proteobacteria, Actinobacteriota, Chloroflexi, and Acidobacteriota, among which, Proteobacteria was the most abundant, with relative abundance in the order of A (28.26%)>Y (26.74%)>YA (22.61%). The relative abundance of Gemmatimonadaceae and Nocardioidaceae increased to 4.06% and 2.43% in Y treatment, respectively, while the relative abundance of Pseudomonas was obviously improved under A treatment (P<0.05). The relative abundance of Microvirga rose in all the three different treatments in comparison with that of the control. The content of soil total nitrogen, total phosphorus, and available phosphorus significantly elevated in Y and YA treatments. RDA suggested the significant correlation of bacterial community structure with soil pH, total nitrogen, available phosphorus, and available potassium (P<0.05), and Spearman correlation analysis suggested the significant or highly significant positive correlation of relative abundance of Pseudomonadaceae with the total nitrogen, total phosphorus, available phosphorus, and available potassium. [Conclusion] Application of A. niger agent alone or in combination with amino oligosaccharin water aqua in watermelon under protected cultivation can improve bacterial diversity, abundance of beneficial bacteria, soil physicochemical properties, and soil fertility. The findings lay a basis for the development of microbial agent with A. niger and the rational application in watermelon cultivation.

Abstract:[Background] Soil fungi dominate the straw decomposition in the field, and straw incorporation and manure application provide nutrients for fungi. [Objective] To study the effect of long-term straw incorporation and manure application on the soil fungal diversity in the field with winter wheat-summer maize rotation. [Methods] Basing on the 14-year location experiment of straw incorporation and manure application in the field with wheat-maize rotation in southern Shanxi province, the study employed high-throughput sequencing to explore the soil fungal community structure and diversity in response to straw incorporation and manure application. The treatments included straw stubble cleaning+unfertilized control (CK), straw stubble cleaning+N and P fertilizers (NP), straw incorporation+N and P fertilizers (SNP), straw stubble cleaning+N and P fertilizers+manure (NPM), and straw incorporation+N and P fertilizers+manure (SNPM). [Results] The richness, Chao1 index, and ACE index of soil fungi in the treatments with straw incorporation and manure were higher than those of CK. A total of 953 OTUs was detected in the five treatment soils. Specifically, CK, NP, NPM, SNP, and SNPM had 398, 451, 472, 462, and 440 OTUs, respectively. A total of 9 fungal phyla were detected, among which Ascomycota, Mucoromycota, and Basidiomycota were dominant and their abundance were significantly different among treatments. A total of 262 fungal genera were detected, among which the three genera with high abundance were Podospora (18.85%), Mortierella (16.67%), and Fusarium (7.77%) in the CK. The top three common genera with high abundance in NP, NPM, SNP, and SNPM were Dendrostilbella, Botryotrichum, and Mortierella, which showed different relative abundance among treatments. According to the cluster analysis, NPM and SNPM with high similarity in fungal community composition and were classified into one category, while CK, NP and SNP were independent categories. The redundancy analysis with environmental factors showed that total nitrogen content was the key factor affecting soil fungal community structure, which was also affected by available phosphorus, pH, available potassium, available nitrogen, and total phosphorus. [Conclusion] Straw incorporation and manure could alter the soil fungal community structure and diversity in the field with winter wheat-summer maize rotation.

Abstract:[Background] Sclerotinia sclerotiorum-induced sclerotiniose in Fritilla ussuriensis is one of the main bulb diseases, which causes huge loss to the industry of F. ussuriensis. [Objective] To screen Trichoderma strains against S. sclerotiorum. [Methods] Eligible strains were identified based on plate confrontation assay, two-sealed-base-plates method, disc filter membrane method, and the test of the inhibitory effect of fermentation broth. Headspace solid-phase microextraction was used to detect the composition of volatile components of Trichoderma strains with better antagonistic effect. The β-1,3 glucanase activity of strains was assayed with the DNS method. Experiment on in vitro bulbs was carried out to verify the effect on S. denigrans. [Results] Strains F1, F2, and D6 had strong inhibitory effect on the growth of S. denigrans and the inhibition rates were 91.06%, 87.00%, and 86.12%, respectively. According to the disc filter membrane test, S. denigrans did not grow on the agar with F2, C6, D3, F4, A26, B30, D4, and D6 and the inhibition rate was up to 100%. The two-sealed-base-plates test indicated that E12 and A26 had the most obvious inhibitory effect, with the inhibition rates of 74.96% and 75.86%, separately. The test on the fermentation broth showed that D3 had the strongest inhibitory effect, which could completely inhibit the growth of S. denigrans (inhibition rate: 100%). The volatile products of A26, D4, E8, E17, and D3 were analyzed by GC/MC, and the antifungal active substances of E17 such as 6-n-pentyl-2H-pyran-2-one were found. F1 was found to have the highest β-1,3 glucanase activity. According to the laboratory test, D3 can significantly inhibit the pathological changes of sclerotiniose in bulbs of F. ussuriensis and has potential biocontrol activity. [Conclusion] Trichoderma D3 has great potential for the control of S. denigrans.

Abstract:[Background] Streptomyces lydicus can efficiently promote the growth of many crops and inhibit many pathogenic fungi. However, there are few studies on the biocontrol effects of S. lydicus on bacterial wilt disease. [Objective] To explore whether S. lydicus M01 can promote tomato growth and inhibit tomato bacterial wilt disease and whether the effect of S. lydicus M01 on tomato growth is achieved by affecting the bacterial community structure in the rhizosphere.[Methods] The effects of S. lydicus M01 on plant growth, bacterial wilt incidence, and rhizosphere bacterial community composition of tomatoes were explored by the greenhouse pot experiments and high-throughput amplicon sequencing. [Results] Compared with the control, S. lydicus M01 increased fresh weight, dry weight, plant height, chlorophyll concentrations measured using soil and plant analyzer develotrnent methods, root vigor, and P content of tomato plants by 22.7%, 12.5%, 16.0%, 28.1%, 18.4%, and 17.9%, respectively. S. lydicus M01 significantly increased plant height, SPAD value, and P content of tomato plants (P<0.05). S. lydicus M01 delayed the onset time of bacterial wilt and decreased bacterial wilt incidence by 41.8% at 9 weeks after pathogen inoculation. Additionally, S. lydicus M01 had no significant effects on rhizosphere bacterial community composition (P=0.4 for microbiome composition at the phylum level and P=0.4 for microbiome composition at the genus level). [Conclusion] S. lydicus M01 can promote plant growth of tomatoes and suppress bacterial wilt of tomatoes, and these effects are not achieved by regulating rhizosphere bacterial community composition.

Abstract:[Background] Understory Panax ginseng grows in the natural environment for many years, and the endogenous bacteria present in its body have stronger adaptability and colonization, which can better play the role of interacting with plants to improve plant resistance and inhibit the growth of pathogenic bacteria. [Objective] To select the dominant strains with strong colonization ability, fast reproductive ability, and antagonistic effects on pathogenic bacteria, understory P. ginseng became the optimal choice. [Methods] The conventional tissue isolation method was used to isolate endophytic bacteria from the root tissues of healthy understory P. ginseng, and the endophytic bacteria with antagonistic effects on ginseng pathogens were screened out by the confrontation test and identified by traditional identification methods. [Results] Among the 6 endophytic bacteria obtained, the strain LXS-N2 had obvious bacteriostatic effects against Rhizoctonia solani and Pythium debaryanum, and it had the characteristics of good colonization and fast reproduction. The strain LXS-N2 inhibited pathogenic fungal growth by destroying the cell wall and membrane of pathogenic fungi and changing hyphae morphology. [Conclusion] The endophytic LXS-N2 was identified as Bacillus velezensis by morphological observation, physiological biochemical reaction, and 16S rRNA gene sequence analysis, which has good application development potential.

Abstract:[Background] The weak transglycosidase activity of β-galactosidase and the hydrolyzable property of the product galactooligosaccharides (GOS) results in the low product yield. [Objective] To study the effect of mutations at highly conserved sites of glycoside hydrolase family 42 (GH42) on the catalytic activity of the β-galactosidase BgaB from Geobacillus stearothermophilus.[Methods] On the basis of the functional analyses of single site mutations, the conserved sites E303 and F341 were cumulatively mutated by the combination of site-directed mutagenesis and chemical modification. [Results] The double-site mutant Ox-E303C/F341S was constructed. Compared with the wild-type enzyme, the double mutations reduced the hydrolysis activity to 30% and increased the GOS yield from 0.75% to 19.50%. [Conclusion] The cumulative mutations of conserved sites enable co-evolution of single-site mutant functions. Reducing the hydrolytic activity and substrate inhibition can improve the transglycosidase activity of β-galactosidases. This work provides a reference for the modification and regulation of the transglycosylating activity of GH42 β-galactosidases.

Abstract:[Background] Hyperuricemia is caused by a significant increase the content of uric acid in the blood, and using probiotic lactic acid bacteria to relieve hyperuricemia has attracted more and more attention. [Objective] To obtain the lactic acid bacteria consortium and pure culture strains with the ability to degrade uric acid. [Methods] We used the MRS medium with uric acid as the substrate to isolate the consortium of lactic acid bacteria degrading uric acid from kimchi. Further, we determined the uric acid degradation ability of the consortium by high performance liquid chromatography. [Results] A consortium of lactic acid bacteria was obtained. After being cultured at 37 °C and pH 6.20 for 72 h, the consortium showed the degradation rate of 12.08% for uric acid. Moreover, after optimization of degradation conditions, the degradation rate was increased to 17.19% after inoculation 72 h under the conditions of beef extract as the single nitrogen source, initial pH 5.00, and 35 °C, and the degradation rate increased by 42.3% compared with that before optimization. Two strains UA-1 and UA-2 with uric acid degradation ability were isolated from the consortium, and their uric acid degradation rates were 10.85% and 8.65%, respectively. The two strains were identified as Lactobacillus buchneri based on morphological characteristics and 16S rRNA sequence. The combination of UA-1 and UA-2 at a ratio of 2:1 showed the uric acid degradation rate of 20.2%, which was 67.22% higher than that of the consortium. [Conclusion] This study proved that the combination of lactic acid bacteria had better degradation effect on uric acid than single strains, which provided data support for the subsequent application use of lactic acid bacteria consortium.

Abstract:[Background] Traditional Shanxi mature vinegar is produced by solid-state fermentation with multiple strains in an open environment. Revealing the composition, interaction network, and source of microbial community facilitates the understanding and regulation of the vinegar fermentation process. [Objective] To reveal the composition, succession, interaction network, and source of microbial community in Shanxi mature vinegar during the fermentation process. [Methods] High-throughput DNA sequencing was performed to reveal the composition, succession, and diversity of the microbial community. SPSS was employed to calculate the Spearman correlation coefficient between species and Gephi was used for the visual analysis of the microbial interaction network. Fast expectation-maximization microbial source tracking (FEAST) was employed to analyze the origin of the microorganisms. [Results] Six bacterial genera and five fungal genera (average relative abundance greater than 1%) were dominant in the fermentation process of Shanxi mature vinegar. The average relative abundance of Acetobacter, Lactobacillus, and Saccharomycopsis were 20.76%, 30.38%, and 46.24%, respectively. The relative abundance of Acetobacter increased gradually during acetic acid fermentation, while the opposite trend was observed for Lactobacillus. The microbial community interaction network showed that Weissella, Lactococcus, Meyerozyma, Loigolactobacillus, Schleiferilactobacillus, and Geobacter had high connectivity (≥7). In addition, Acetobacter demonstrated significant antagonism with Weissella, Schleiferilactobacillus, Loigolactobacillus, Lactococcus, and Meyerozyma. The results of source tracking showed that 1.02% of bacteria and 77.04% of fungi were derived from Daqu on the second day of saccharification. On the first day of acetic acid fermentation, 0.93% of bacteria and 52.82% of fungi were derived from fermented grains. [Conclusion] This study provided important theoretical data for understanding the composition, succession, and interaction network of microbial community and tracking the source of microorganisms during the fermentation process of Shanxi mature vinegar.

Abstract:[Background] The virulence and drug resistance of Salmonella spp. as a major zoonotic pathogen have attracted widespread attention. [Objective] To investigate the virulence and drug resistance of Salmonella enterica subsp. enterica serovar Dublin isolated from a dead calf in Tongliao City. [Methods] Bacterial isolation and 16S rRNA gene sequencing were performed with the lung of a dead calf, and the pathogen was identified as Salmonella. Animal tests, drug sensitivity tests, and PCR were employed to examine the virulence gene, drug resistance, virulence, and drug resistance genes of the isolate, and the whole genome was sequenced. [Results] The isolate had strong virulence, with the median lethal dose of 2.8×10⁶ CFU/mL to mice. It was multidrug-resistant, sensitive to only polymyxin B and cephalothin, and moderately sensitive to doxycycline and enrofloxacin. The detection rate of 13 virulence genes was 92.3%. The whole genome of the isolate had the length of 4 965 370 bp and the GC content of 52.12%, and it carried two plasmids with the lengths of 79 524 bp (pTLS-1) and 45 301 bp (pTLS-2), respectively. The isolate carried 996 virulence genes and 24 pathogenicity islands. A total of 42 drug-resistant genes were detected, among which 4 were horizontal transferable genes. In addition, there were 9 mobile genetic elements in the genome, including insertion sequences, transposons, etc. [Conclusion] The Salmonella Dublin strain isolated from a calf was virulent and multidrug-resistant, carrying a large number of virulence genes and drug-resistant genes.

Abstract:[Background] As a valuable hemicellulase, α-l-arabinofuranosidase (EC 3.2.1.55) can degrade xylan with other hemicellulases and is applied in food, medicine, and biomass energy conversion. [Objective] This study aimed to clone a novel α-l-arabinofuranosidase gene and analyze the heteroexpression, purification, and enzymatic properties of the protein. [Methods] The α-l-arabinofuranosidase gene was amplified from the fecal microbial metagenome of Nomascus concolor and heterologously expressed in Escherichia coli BL21(DE3), and then the enzymatic properties of the protein were examined. [Results] After α-l-arabinofuranosidase gene AbfNC2b_38 was amplified from the fecal microbial metagenome, a recombinant protein AbfNC2b_38 with a molecular weight of 57.04 kDa was expressed. At the optimum conditions of 55 °C and pH 6.0, the enzyme showed the K_m of (6.48±0.73) mmol/L, the V_max of (1 248.0±114.6) U/mg, and the highest specific activity of 300.81 U/mg compared with the α-l-arabinofuranosidases of other metagenomic sources. This enzyme was highly tolerant to ethanol and NaCl. It showed the relative activity of 68% after being treated with 30% ethanol for 1 h and relative activity of approximately 70% after being exposed to 25% NaCl for 1 h. Moreover, it had the highest synergistic rate of 1.21 when synergistically degrading beech xylan with xylanase. [Conclusion] A novel α-l-arabinofuranosidase gene AbfNC2b_38 was cloned from the fecal microbial metagenome of N. concolor, which was successfully heterologously expressed. AbfNC2b_38 was highly tolerant to both ethanol and NaCl, and can cooperate with xylanase to improve the degradation efficiency of xylan. Hence, this enzyme is of significant application potential in feed and food processing.

Abstract:[Background] Nocardiosis has a long incubation period and long disease duration, with high infection rate and mortality rate, which brings serious economic losses to aquaculture. Nocardia seriolae, the pathogen causing Nocardiosis, is an intracellular bacterium. The main pathogenesis of this disease is the chronic infection of N. seriolae. This pathogen invading largemouth bass (Micropterus salmoides) can cause white nodules, the products of the interaction between pathogen and macrophages. The bacteria are wrapped by necrotic cells in the white nodules, which make it difficult for antibiotic to kill the bacteria, resulting in death of fish. [Objective] To establish an in vitro model for the infection of largemouth bass head kidney macrophages by N. seriolae, observe the progression of infection, and elucidate the infection-induced apoptosis of macrophages. [Methods] The macrophages were isolated by density gradient centrifugation and identified by morphological observation, specific staining, and PCR amplification of macrophage-expressed gene mpeg1. The activity and function of macrophages were detected by CCK-8 method and oxygen respiratory burst activity assay. The morphological and quantitative changes of N. seriolae and macrophages during infection were observed via inverted fluorescence microscopy and flow cytometry. The apoptosis of macrophages was investigated by double fluorescence flow cytometry, lactate dehydrogenase (LDH) release assay, and mitochondrial membrane potential assay. [Results] High-purity macrophages were isolated from head kidney of largemouth bass and were identified as macrophages by staining and PCR methods. The medium was optimized as 1640 medium + 1% penicillin-streptomycin + 1% fetal bovine serum, in which the cells could survive for 72 h in vitro, with the survival rate as high as 80%±1.03% within 24 h. The oxygen respiratory burst activity of macrophages enhanced after lipopolysaccharide stimulation (P<0.05). The GFP-N. seriolae were phagocytosed by the macrophages at 2 h, became rounded with decreased adherence rate at 4 h, and proliferated and surrounded the macrophages at 6 h. A number of macrophages died at 8 h. The initial stage of infection witnessed the increase in the apoptosis rate of macrophages, the increase in the release of LDH, and the decrease in the mitochondrial membrane potential. With the prolongation of infection, the apoptosis rate, the amount of LDH released, and the mitochondrial membrane potential decreased. It implied that apoptosis was promoted in the initial of infection and then inhibited as the infection prolonged. [Conclusion] This study successfully established an in vitro model for the infection of largemouth bass head kidney macrophages by N. seriolae. It confirmed that N. seriolae infected and survived in macrophages by inhibiting apoptosis. This study provided information for further studying the interaction between N. seriolae and macrophages and elucidating the pathogenic mechanism of N. seriolae.

Abstract:[Background] Vespa mandarinia Smith can control a variety of field pests and has medicinal values. The structure and function of gut bacteria in V. mandarinia remain to be studied. [Objective] To obtain the culturable bacteria from the gut of V. mandarinia and screen out the bacterial strains capable of producing digestive enzyme, so as to provide a basis and research materials for understanding the influence of gut bacteria on the host and for utilization of the functional bacterial strains. [Methods] The gut bacteria of V. mandarinia were isolated by the culture method, and 16S rRNA gene sequencing was employed to identify the strains. Halo-forming method was adopted to screen out the strains producing protease, lipase, amylase, and cellulase, and the ratio of halo diameter (D) to bacterial colony diameter (d) was used to compare the strain capability of producing digestive enzymes. [Results] A total of 10 species of bacteria belonging to 6 genera were isolated from the gut of V. mandarinia, including 5 species of Bacillus, 1 species of Enterococcus, Staphylococcus, Leuconostoc, Lactococcus, and Acinetobacter, respectively. Six strains producing digestive enzymes were screened out from the 61 strains obtained. Among them, B. thuringiensis V44 had the ability to produce protease, amylase, lipase, and cellulase. E. faecalis V6 was capable of producing amylase, protease, and lipase. B. cereus V43 can produce protease, amylase, and cellulase. E. faecalis V20, B. cereus V19, and B. wiedmannii V22 demonstrated the ability to produce protease. [Conclusion] The gut bacteria resources of V. mandarinia were abundant, and some strains were capable of producing digestive enzymes, which can facilitate the digestion and affection of health of V. mandarinia. All the 6 strains screened out in this study could produce protease. Strains V43 and V44 showed the strongest ability to produce amylase and lipase, respectively, which could be further developed as gut functional strain resources.

Abstract:[Background] Vibrio mimicus, a common Gram-negative pathogen, is widely distributed in the aquatic environment and often involved in infectious diseases of aquatic animals and humans. Multilocus sequence typing (MLST) has been applied to the molecular typing of many pathogens, which allows for investigations into genetic relatedness between different strains, therefore provides insights into bacterial evolution and epidemiology. However, no report is available on the MLST of V. mimicus. [Objective] To develop a powerful MLST typing method for V. mimicus and then apply it to analyze the population structure and genetic evolution of different V. mimicus strains, and eventually provide theoretical references for the prevention and control of diseases caused by V. mimicus infection. [Methods] Seven housekeeping genes (dnaE, gyrB, mdh, recA, rpoD, pntA, and pyrH) of V. mimicus, were selected as target genes for MLST, and their conserved fragments were obtained by polymerase chain reaction (PCR) from a total of 155 V. mimicus strains isolated from the aquaculture area in Jiangsu and sequenced. All unique DNA sequences were assigned alleles, made allelic profiles, and assigned different sequence type (ST). The clonal complex and genetic evolution tree clustering of the assigned ST types were analyzed using goeBURST-1.2.1 and MEGA-X. In addition, antibiotic sensitivity of the 155 V. mimicus strains was tested using the Kirby-Bauer disk diffusion method. [Results] The 155 V. mimicus strains were divided into 56 STs, among them ST11 had the highest proportion. At the level of double locus variants (DLV), 56 STs were further divided into three clonal complexes and three monomers. Phylogenetic tree showed that 56 STs fell into three clusters (cluster I, cluster II, and cluster III). The Kirby-Bauer disk diffusion assay showed that the 155 V. mimicus strains exhibited the highest resistance to erythromycin (88.39%, 137/155) and the highest sensitivity to chloramphenicol (91.61%, 142/155). [Conclusion] The MLST method established in this study displays good resolution and can be used as a molecular typing tool for phylogeny and future epidemiological investigation of V. mimicus. Antibiotic resistance profiles suggest that florfenicol, one of antibacterial agents that approved for application, can be used for the treatment of V. mimicus infections in the aquaculture process.

Abstract:[Background] Staphylococcus aureus is a major bacterial pathogen causing infections in food and human body, and there is an urgent need to develop new antibacterial agents. [Objective] To study the effects of the pyrazolone-copper complex P-FAH-Cu-phen on the transcriptome and main metabolic signaling pathways of S. aureus. [Methods] The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of P-FAH-Cu-phen on S. aureus were determined by liquid dilution method. The S. aureus in the logarithmic growth phase was treated with P-FAH-Cu-phen at the final concentration of 2 μg/mL for 30 min and 2 h, respectively, and then the transcriptome was sequenced and analyzed. [Results] The MIC and MBC of P-FAH-Cu-phen on S. aureus were 2 μg/mL and 4 μg/mL, respectively. Compared with the blank control, P-FAH-Cu-phen treatment for 30 min led to 356 differentially expressed genes (DEGs), including 180 up-regulated genes and 176 down-regulated genes. P-FAH-Cu-phen treatment for 2 h resulted in 23 DEGs, including 3 up-regulated genes and 20 down-regulated genes. The DEGs were mainly enriched in membrane components, cytoplasm, plasma membrane, ATP binding, pathogenesis, metal ion binding, histidine biosynthesis process, DNA binding, hydrolytic enzyme activity, transmembrane transporter activity, nitrate assimilation, nitrate metabolism process, nitrate reductase complex, nitrate reductase activity, etc. The signaling pathways involving the DEGs mainly included two-component system, quorum sensing, nitrogen metabolism, tricarboxylic acid cycle, amino acid metabolism and so on. [Conclusion] P-FAH-Cu-phen may inhibit S. aureus by affecting plasma membrane composition, toxin production, biofilm formation, cell wall synthesis, and energy metabolism. The study provides a theoretical basis for revealing the molecular mechanism of the inhibition on S. aureus by P-FAH-Cu-phen.

Abstract:[Background] Traditional primer extension assay usually uses radioactive probes to identify the start sites of transcription and processing sites of transcripts. However, the application of this method in general laboratories is limited because of the short half-life, health hazards, and waste disposal issue of radioisotope-labeled primers. [Objective] To develop a non-radioactive method of primer extension by employing near-infrared fluorescent cyanine dye Cy5.5 and then employ this method to identify the RNA cleavage sites of bacteria. [Methods] The sequence harboring RNA cleavage sites was inserted into the dual-luciferase reporter assay system, and then the Cy5.5-labeled oligonucleotides primer specific to mcherry was used for primer extension. The RNA cleavage sites were precisely identified by Northern blotting and Cy5.5-based primer extension technique. [Results] Two processing sites of cip-cel mRNA were identified, which located in the downstream region of the stem-loop. However, no conserved sequence was identified near the processing sites. [Conclusion] Compared with radioactive isotope-based primer extension methods, the Cy5.5-based primer extension technique not only efficiently determines processing sites of RNA molecules but also avoids the use of hazardous radioactive isotope reagents for labeling and shortens the processing time, which suggests that the Cy5.5-labeled probe is suitable for primer extension assay.

Abstract:[Background] Compared with chemical degumming, biological degumming of hemp is environmental-friendly. [Objective] To obtain an efficient pectinase-producing strain for the biological degumming of hemp. [Methods] The strains were screened by plate dilution method in the medium with pectin as the sole carbon source, and the target strain was identified by physiological and biochemical tests and 16S rRNA gene sequence alignment. The enzyme production conditions were optimized by single factor experiment, and the biological degumming effect of hemp was verified under the optimal conditions. [Results] A highly active pectinase-producing strain, Pectobacterium aroidearum WNH, was screened out. After culture for 16 h at 27 °C, the rotation speed of 160 r/min, inoculum volume of 10%, and initial pH 7, the crude enzyme solution of P. aroidearum WNH showed the pectinase activity of 155.03 U/mL. Under the above conditions, the second degumming of hemp bast was carried out, and the degumming rate reached 27.18%, which was 6.93% higher than that of the control group. [Conclusion] P. aroidearum WNH has the potential for the biological degumming of hemp.

Abstract:Phosphorus (P) is a finite and non-renewable resource. Soil P deficiency is a main limiting factor for crop growth and agricultural production. Once entering into soils, inorganic P (P_i) in fertilizers is readily being fixed by soil solid phase, binds to metal ions to form the insoluble complex, or transform into organic P (P_o) which fails to be directly uptake by plants. Soil P mainly exists as P_o, which accounts for 20%-80% of total P. Phytic acid or phytate is the predominant form of P_o, accounting for about 50% of P_o. Phytate can not be directly uptake by plants, while can release P via dephosphorylation by the specific enzyme phytase. Phytase is mainly secreted by microbes and its activity is affected by temperature, pH, soil adsorption, Ca content, Ca/P ratio and substrate concentration and availability, leading to reduced activity or inactivation. Therefore, it is of great importance for reducing the application of exogenous P fertilizer and ensuring agricultural production to understand how to maintain or improve phytase activity in soils and improve the utilization of soil endogenous phytate. Thus, this paper reviews the sources, classification, and function mechanisms of microbial phytase and influencing factors of soil phytase activity, focusing on methods to maintain or improve phytase activity and the application efficiencies. In terms of the low activity and poor stability, methods to improve phytase properties including adjusting optimal pH range, improving thermal stability, loading phytase on nano-materials, and genetic engineering, are proposed. As such, this review is expected to help better understand the influencing factors of phytase activity in soil and provide theoretical and technical supports to improve endogenous phytic acid utilization efficiency. This is of great importance to reduce the application rate of P fertilizer, P loss, and risk of soil non-point source/water pollution and ensuring agricultural sustainable development.

Abstract:Stropharia rugosoannulata, one of the cultivated edible fungi recommended by the Food and Agriculture Organization of the United Nations to developing countries, degrades crop straw, tree branches, fallen leaves, etc. The fruiting bodies are nutritious and delicious and the dregs can improve the soil environment. Thus, this species plays an important role in ecological agriculture and forestry and circular economy. In this paper, the biological basis, nutrients in fruiting body, and bioactive components of S. rugosoannulata and its application in the fields such as ecological agriculture and forestry and environmental restoration were summarized. This review is expected to serve as a reference for utilization of S. rugosoannulata and further development of the relevant industries.

Abstract:Polysaccharides, a major group of active components in the medicinal Ganoderma spp., are mainly extracted from the fruiting body, spore powder, and liquid submerged fermentation broth of mycelium and extracellular fluid. In recent years, polysaccharides extracted from the mycelia and extracellular fluid have attracted wide attention from scholars. In this paper, the effect of composition of fermentation medium and fermentation conditions on the intracellular and extracellular polysaccharides of Ganoderma spp., and the structures and biological activities of the polysaccharides were reviewed, which could lay a theoretical basis for the development and utilization of the polysaccharides produced by liquid fermentation.

Abstract:The cell membrane of Sphingomonas contains glycosphingolipids, which is more hydrophobic than lipopolysaccharide. In addition, since Sphingomonas has efficient metabolic regulation mechanism and gene regulation ability, it has significant application potential in welan gum synthesis, environmental remediation, and promotion of plant growth. However, research on genomics in China has not been paid enough attention, resulting in no breakthrough in the research on the metabolic mechanism of Sphingomonas. Therefore, this paper reviewed the systematic classification, genomics, metabolic regulation mechanism, and application of Sphingomonas and analyzed the metabolic mechanism of welan gum produced by Sphingomonas from the genetic level, providing a theoretical basis for the subsequent studies on high-density fermentation and industrial production of Sphingomonas, and thereby further developing its potential application in biotechnology.

Abstract:Ubiquitous ciliate-algae symbiosis plays a key role in the water environment. In this review, we summarized the current knowledge on ecological functions of ciliate-algae symbiosis. Moreover, the steps of symbiosis establishment and the interactions between Paramecium bursaria and Chlorella sp., the symbiotic relationship and interaction between Mesodinium rubrum and cryptophytes were summarized. Furthermore, several key biological questions on ciliate-algae symbiosis were raised, including the molecular mechanisms of the functions of Paramecium digestive vacuole (DV) and perialgal vacuole (PV) membrane, the establishment process of the symbiosis between M. rubrum and cryptophytes, and the roles of M. rubrum in the symbiotic process. Finally, we prospected the future directions on ciliate-algae symbiosis study.

Abstract:With the development of medical disciplines and technological innovation, the knowledge related to microbiology is constantly developing and updating. We analyzed the problems emerged with the cutting-edge ideas and knowledge in the teaching of Medical Microbiology. These problems are caused by the new progress in research of microbiota and human health, evolution of microbial classification, updated understanding of microbial structure, contradiction between organ-system-based knowledge system and taxonomy-based knowledge system, etc. Furthermore, we discussed the possible solutions of reconstructing the teaching content, applying diversified teaching methods, and introducing the organ-system-based knowledge system. With the advancement of ‘New Medicine’ education in China, it is imperative to reform the teaching content of Medical Microbiology, so as to adapt to the development of medical disciplines and achieve the goal of talent cultivation.