Abstract:[Background] Due to the aggravating harm of petroleum-based plastic products to humans and the environment, polyhydroxyalkanoates (PHA) are becoming increasingly popular as new biodegradable plastic materials. However, the high production cost restricts the popularization and application of PHA. Screening the strains with high PHA yield for mass production is a key solution to this problem. [Objective] To explore the strain resources capable of synthesizing PHA and screen out and identify the high PHA-yielding bacteria from extreme environments. [Methods] The strain was isolated and purified by nile blue A plate culture and PCR methods. The 16S rRNA gene was sequenced for the identification of the strain and the construction of the phylogenetic tree in MEGA 6.0. Finally, the accumulation of PHA in the strain under different conditions was quantified by Nile red staining and gas chromatography. [Results] A strain with high yield of PHA was isolated from the garbage sediment of a saline-alkali land. The amplification of PhaC confirmed that the strain had the ability to synthesize PHA. Based on the 16S rRNA gene, the strain was identified as Pseudomonas brassicacearum and named NP-2. Furthermore, the culture conditions of strain NP-2 were optimized and the maximum accumulation of PHA reached 3.78 mg/mL at the time point of 48 h. [Conclusion] NP-2 belongs to P. brassicacearum and has high production of PHA. This study provides resources of high PHA-yielding strains in extreme environment for the production of PHA and accumulates data for further mining high PHA-yielding strains.

Abstract:[Background] The metabolites of marine microorganisms are considered ideal sources for discovering natural active substances, which inevitably include novel quorum sensing inhibitors (QSIs). Response surface method uses multivariate quadratic regression model to fit the relationship between each factor and response value and evaluate the effects of factors and their interaction, which can effectively screen out the best conditions of the factors affecting the microbial fermentation for metabolite production. [Objective] The quorum sensing inhibitory activity of the crude extract of the marine bacterial strain Vibrio sp. LA-05 was investigated with Chromobacterium violaceum ATCC 12472^T as the indicator strain. To improve the production of active substances in the crude extract, we employed response surface method to optimize the fermentation conditions of the strain on the basis of single factor experiments. [Methods] After preliminarily screening by the agar plate diffusion method, the growth curves and violacein production of C. violaceum ATCC 12472^T were employed to evaluate the quorum sensing inhibitory activity of the crude extract. On the basis of single factor experiments, fermentation conditions were optimized by Box-Behnken design and response surface method with violacein inhibition rate as a response value to improve the production of active substances in the crude extract. [Results] Within the concentration range that did not affect the growth of C. violaceum ATCC 12472^T, the crude extract inhibited the production of violacein to various degrees. The fermentation conditions were optimized as fermentation with the inoculum amount of 2.37% at 19.28 ℃ and 154.21 r/min for 37.59 h, the extract obtained under which had the expected inhibition rate of 53.38%. The verification experiment showed that the inhibition rate of violacein was 52.85%±0.64%, close to the model predicted value. This result indicated that the regression model had a good fitting degree with the experimental results, being reliable and feasible. [Conclusion] The crude extract of the marine bacterial strain Vibrio sp. LA-05 possesses quorum sensing inhibitory activity. The fermentation conditions of this strain are optimized by response surface method, which will lay a foundation for the research and development of novel QSIs.

Abstract:[Background] The environmental resilience of scleractinian corals is related to the associated bacteria. However, it is unclear how these bacteria adapt to the environmental changes. Studying the biological and ecological roles of these bacteria isolated via pure culture method is a fundamental approach to decipher the environment adaptation mechanism of corals. [Objective] To study the diversity and function of the heat-tolerant bacteria associated with two species of corals and further provide new insights into the environmental resilience of scleractinian corals. [Methods] We used three media, 2216E, seawater GYP, and seawater R₂A agar, to isolate the heat-tolerant bacteria associated with two coral species (Acropora pruinosa and Galaxea fascicularis) with significant differences in heat tolerance from Weizhou Island, Beibu Gulf at 32 ℃ (heat tolerance threshold of corals). The 16S rRNA gene sequencing and sequence similarity analysis were then performed for the isolated bacteria. Predominant strains were selected and tested for the heat tolerance, and their antibacterial activity was analyzed by the plate confrontation method. [Results] The diversity of the potential heat-tolerant bacteria showed significant difference between the two coral species. A total of 44 strains of potential heat-tolerant bacteria belonging to 22 genera of 4 phyla were isolated from A. pruinosa, among which Vibrio, Pseudoalteromonas, and Tenacibaculum were predominant. A total of 28 heat-tolerant bacterial strains belonging to 11 genera of 3 phyla were isolated from G. fascicularis, among which Vibrio, Pseudoalteromonas, and Rugeria were predominant. Among the isolated bacteria, 17 strains shared the 16S rRNA gene sequence similarity below 98.65%, which might be new taxa. The growth conditions of bacteria were studied at 26-37 ℃, which showed the optimal growth temperature was 34 ℃, higher than the optimal growth temperature of most marine bacteria and coral bleaching threshold, indicating that the isolated bacteria had potential heat resilience. Two strains of Rugeria had an inhibitory effect on Vibrio, a potential pathogen associated with coral diseases, and 3 strains of Tenacibaculum did not exert significantly inhibitory activity. [Conclusion] The diversity of bacteria associated with A. pruinosa and G. fascicularis is high and needs to be further researched. Although the opportunistic pathogen Vibrio was the predominant genus, the bacteria associated with G. fascicularis had an inhibitory effect on it. Based on the above results, we hypothesized that the heat resilience of scleractinian corals was related to the inhibitory effect of the coral-associated bacteria on pathogenic bacteria.

Abstract:[Background] In recent years, Huanglong travertine landscape has seen large-scale growth of algal mats with thickness of 3–5 cm, posing a threat to the travertine deposition and affecting the ornamental value of the landscape. [Objective] To dissect the structure of the algal mats and the reasons for the large-scale growth, thereby to control the growth of algae, and to propose management methods. [Methods] The composition of eukaryotic species in different layers of typical epiphytic algal mats in the Huanglong travertine area was analyzed based on PE-250. Their morphology was characterized via the field emission scanning electron microscope, and the correlation between the thickness of algal mats and water environment parameters was examined. [Results] The algal mats were home to about 400 species of eukaryotes, with the dominant algae of Diatomea (mainly Cymbella), Rotifera, and Streptophyta. Non-metric multidimensional scaling (NMDS) analysis and clustering analysis showed that the composition of eukaryotic species in the middle layer of the algal mats was highly similar to that in the lower layer. Diatoms dominated the upper layer, and the middle layer was mainly composed of filamentous algae. For the lower layer, travertine particles were seen in the reticular structure composed of filamentous algae. The thickness of algal mats was mainly in positive correlation with the total nitrogen (TN), total phosphorus (TP), and dissolved oxygen (DO) in the water (p<0.05). [Conclusion] The algal mats boast abundant species in a few phyla. The three layers of the mat are distinct from each other in species composition and microstructure and water eutrophication can explain the rapid growth of algal mats. This study lays a theoretical basis for the management of algal blooms in Huanglong Scenic and Historic Interest Area.

Abstract:[Background] Azo dyes and their degradation products are highly toxic and have carcinogenic, teratogenic, and mutagenic effects on organisms. Using co-metabolism to enhance the degradation and removal efficiency of azo dyes by pure cultured bacterial strain or co-cultured flora is environmentally friendly, whereas the comparative study on different efficiencies and mechanisms of bacterial flora/strain under co-substrate regulation needs to be further studied. [Objective] To investigate the efficiencies and mechanisms of functional flora DDMZ1 and strain DDMZ1-1 (identified as Burkholderia sp.) in the degradation and decolorization of reactive black 5 (RB5) enhanced by fructose as a co-substrate. [Methods] The culture conditions of functional flora/strain were optimized, and the decolorization performances and azoreductase activities of functional flora/strain enhanced by fructose co-metabolism were determined. The identification and toxicological assessment of RB5 degradation products were performed by the liquid chromatography/time-of-flight/mass spectrometry (LC-TOF-MS) and phytotoxicity test. The broad-spectrum decolorization performances of functional flora/strain on decolorizing dyes with varied structures were compared and investigated. [Results] The removal efficiencies of RB5 by the functional flora DDMZ1 and Burkholderia sp. DDMZ1-1 under the optimal conditions (pH 5.5, 37 ℃) were 79% and 73%, respectively, and the functional flora exhibited stronger adaptive advantages to the high-salinity environment. The addition of fructose significantly stimulated the decolorization performance of functional flora/strain to RB5 with different initial concentrations. Compared with the flora/strain samples without fructose, those with fructose increased the removal efficiencies of 200 mg/L RB5 by nearly 21% and 27%, respectively. The sample FRU200 (with fructose) significantly stimulated functional flora/strain to secrete extracellular azoreductases after 24 h, thus enhancing the enzyme activity. LC-TOF-MS analysis indicated that RB5 was biodegraded into various metabolites with low molecular weights and simple structures in the fructose co-metabolic system of functional flora DDMZ1. The phytotoxicity of RB5 degradation products in the flora/strain system was significantly reduced via fructose co-metabolism. Compared with Burkholderia sp. DDMZ1-1, the functional flora DDMZ1 exhibited a stronger broad-spectrum degradation ability to dyes with varied structures. [Conclusion] Compared with Burkholderia sp. DDMZ1-1, the functional flora DDMZ1 has better removal efficiency, functional enzyme activity, and product detoxification of RB5 enhanced by fructose co-metabolism. This paper provides a theoretical basis for the application of co-substrate bioaugmentation technology in the treatment of wastewaters containing azo dyes.

Abstract:[Background] Airborne microbes are a key component of the urban ecosystem, the concentration of which has great significance for monitoring urban air quality, controlling environmental pollution, and preventing disease. [Objective] To analyze the distribution characteristics of airborne microbes in Lhasa of China and explore the effects of meteorological factors and air particulate matter on the distribution of airborne microbes. [Methods] The airborne microbes were stained by SYBR Green I and observed under an epifluorescence microscope. The seasonal concentrations of the microbes from October 2019 to October 2020 were determined. Furthermore, the correlations of the concentration of airborne microbes with meteorological factors and environmental indicators were studied. [Results] The airborne microbes appeared bright green, oval, with a diameter of 0.5-1.0 μm and attaching to the organic matter and black carbon. The concentrations of total microbes in Lhasa ranged from 3.10×10³ to 2.38×10⁴ cells/m³. The concentrations of airborne microbes in two forms (free-floating and particle-attached) were the highest in winter. The concentration of free-floating microbes was the lowest in autumn, which was significantly different from that in winter (P<0.05). The concentration of particle-attached microbes showed no significant difference among four seasons. Furthermore, the concentration of airborne microbes was not significantly correlated with meteorological factors, while it had a significant positive correlation with the concentration of air particulate matter (P<0.05). [Conclusion] The concentration of airborne microbes in Lhasa was at a low level compared with that in other cities and affected by air pollutants.

Abstract:[Background] Heavy metal pollution of roads becomes more and more serious, and it is urgent to find efficient microbial resources for environmental remediation. [Objective] To screen heavy metal-resistant strains from the soil of road forest belt in Urumqi of China and test the heavy metal-removing ability. [Methods] Four media containing five heavy metal ions (Pb, Cd, Zn, Cu, and Ni) were used to screen the resistance strains which were then identified based on morphological characteristics and 16S rRNA gene. The removal of heavy metal ions by the strains was tested by inductively coupled plasma optical emission spectrometer (ICP-OES). [Results] Among the four media, TSA was the optimal one for the screening of strains. A total of 16 resistance strains were screened out: 4 Pb-resistant strains (tolerant concentration: 3 000 mg/L), 4 Cd-resistant strains (tolerant concentration: 800 mg/L), 4 Zn-resistant strains (tolerant concentration: 600 mg/L), 3 Cu-resistant strains (tolerant concentration: 300 mg/L), and 1 Ni-resistant strain (tolerant concentration: 400 mg/L). Among the 16 strains, the majority were Bacillus. The removal rate of 700 mg/L Pb²⁺ by strain Pb6 stood at 92.48%, and the removal rates by strains Pb11, 3 and 9 hit 27.70%, 40.37%, and 58.88%, separately. The removal rate of 200 mg/L Cd²⁺ by strain Cd4 was the highest (63.84%), and the removal rates by other Cd-resistant strains were about 30%-40%. The removal rates of 200 mg/L Zn²⁺ by strains Zn1 and Zn4 were 65.34% and 60.87%, respectively, while those by strains Zn5 and Zn6 registered 15.78% and 12.60%, separately. The removal rates of 300 mg/L Cu²⁺ by the three Cu-resistant strains were low (<3%). The removal rate of 200 mg/L Ni²⁺ by strain Ni2 was 4.31%. The strains (except for Cu1 and Cu3) mainly removed the heavy metals by adsorption, supplemented by absorption. After UV irradiation of strains Pb6, Cd4, and Zn1 for 30 s and continuous subculture, the removal rates of the corresponding heavy metals by three stable strains were 91.11%, 65.10%, and 66.48%, respectively. [Conclusion] Three strains with high tolerance to and removal rate of heavy metals were screened out: Bacillus sp. Pb6, Pseudomonas sp. Cd4, Bacillus sp. Zn1, which can be used as candidate strains for the remediation and treatment of soil or water polluted by heavy metals.

Abstract:[Background] In recent years, aniline compounds have aggravated the pollution of ecological environment, and biological treatment of aniline wastewater has great development potential and broad application prospect. [Objective] To isolate a strain that can degrade aniline efficiently from activated sludge contaminated by aniline compounds for a long term, and optimize its medium and degradation conditions to provide strain and gene resources for aniline bioremediation. [Methods] The high-efficient degrading bacteria with aniline as its sole carbon and nitrogen source and energy were screened out from the enriched and acclimated strains by plate method. The strain was identified by 16S rRNA gene sequence analysis. The degradation conditions were optimized by the single factor screening test, and the culture conditions were optimized by the orthogonal experiment. [Results] An aniline-degrading strain BA-6 was screened out and identified as Microbacterium sp. The strain removed more than 98% aniline with the initial concentration of 600 mg/L within 24 h. The efficient degradation temperature and pH for the strain BA-6 were 30-37 ℃ and 6.5-7.5, respectively. The substrate utilization test showed that the strain BA-6 had the ability to degrade many aniline compounds. The optimal fermentation medium was obtained, and the viability of the strain was up to 3.06×10¹⁰ CFU/mL. [Conclusion] Based on the strong abilities to degrade aniline and adjust to the environment, BA-6 strain has certain application potential in the remediation of ecological pollution of aniline compounds.

Abstract:[Background] Antibiotic pollution has aroused increasing concern. Degradation of environmental antibiotics by biological methods is considered to be an environmentally friendly approach to deal with antibiotic contamination. [Objective] To screen out a bacterial strain with efficient lincomycin degradation and study its degradation mechanism. [Methods] The strain was identified based on physiological and biochemical characteristics and 16S rDNA sequence. The antibiotic resistance genes were identified by PCR and the degradation products of lincomycin by mass spectrometry. [Results] An efficient lincomycin-degrading strain Pseudomonas RST-1 was isolated from a lincomycin mycelia dreg composting sample. After incubation in the beef extract peptone medium with 3.0 g/L lincomycin for 40 h, Pseudomonas RST-1 degraded up to 57.3% of lincomycin. The strain carried antibiotic resistance genes such as intI1, sul1, and sul2. The results of mass spectrometry revealed that lincomycin was degraded into demethyllincomycin and 2-propyl-N-methylproline. [Conclusion] The strain RST-1 has the ability to degrade lincomycin efficiently, which may be achieved through demethylation and amide bond hydrolysis. These results laid a foundation for the construction of lincomycin-degrading strains and development of efficient degradation microbial agents.

Abstract:[Background] Anaerobic oxidation of methane (AOM) includes denitrification- dependent anaerobic methane oxidation and sulfate reduction-dependent anaerobic methane oxidation. At present, the excessive discharge of nitrogen and sulfur pollutants into water causes serious environmental pollution and ecological damage. [Objective] We used the AOM-microbial fuel cell (MFC) to study the coupling reaction mechanism of simultaneous nitrogen and sulfur removal and the microbial diversity changes during the reaction. [Methods] We constructed three MFCs (N-S-MFC, N-MFC, and S-MFC) with methane as the sole carbon source to explore the simultaneous nitrogen and sulfur removal performance. The 16S rRNA gene high-throughput sequencing was employed to analyze the microbial community structure. [Results] The removal rates of nitrate and sulfate in N-S-MFC were 90.91% and 18.46%, respectively. The relative abundance of microorganisms in the anode chamber increased, and the microorganisms involved in denitrification and sulfate reduction were enriched. Specifically, the relative abundance of common methanotrophs including Bacteroidota, Firmicutes and Desulfobacterota at the phylum level and Methylobacterium_Methylorubrum, Methylocaldums and Methylomonas at the genus level was increased. [Conclusion] N-S-MFC promotes nitrate reduction while having little effect on sulfate reduction. This study provides a theoretical basis for the application of methane MFC in simultaneous nitrogen and sulfur removal from wastewater.

Abstract:[Background] In recent years, the health benefits of Latilactobacillus curvatus have received much attention and genome analysis combined with phenotypic test provides a new approach for the development of probiotics. [Objective] To explore the genomic characteristics and probiotic properties of L. curvatus HFS9 isolated from healthy human feces. [Methods] The genome of L. curvatus HFS9 was characterized by pan-genome analysis and genomic annotation was performed to identify the probiotic genes. The probiotic properties of L. curvatus HFS9 in vitro were assessed based on survivability in low pH and 0.3% bile salt, self-aggregation capacity, hydrophobicity and cell adhesion, susceptibility tests, radical scavenging activities, and antibacterial experiments. The mouse model of colitis was established to evaluate the anti-inflammatory effect of HFS9 in vivo. [Results] L. curvatus had an open pan-genome and a conserved core genome. The genome of L. curvatus HFS9 was 1.97 Mb, with the GC content of 41.86% and 2 050 coding sequences. It carried Lactobacillus phage PLE3 genes and possessed the probiotic genes related to cell adhesion, acid tolerance, bile salt tolerance, and antioxidation. The survival rates of L. curvatus HFS9 in acid and bile salt environments were 62.42% and 92.92%, respectively. The self-aggregation capacity and hydrophobicity of L. curvatus HFS9 were 63.33% and 75.00%, respectively. L. curvatus HFS9 showed the adhesion rate of 12.97% to human colon cancer cells (HT-29 cells), was sensitive to most of the antibiotics tested, had inhibitory effects on six common human pathogens, and possessed the abilities to scavenge 1,1-diphenyl-2-picrylhydrazyl radical 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) and hydroxyl radicals. In addition, L. curvatus HFS9 relieved the symptoms and ameliorated colon shortening and histopathological changes in the mouse model of colitis. [Conclusion] L. curvatus HFS9 contains probiotic genes and has probiotic properties in vitro and in vivo, which can be further developed and utilized as a candidate probiotic strain.

Abstract:[Background] The brain-gut axis theory suggests that there is a potential link between intestinal flora and depression, but the current research is controversial, and the specific link is not yet determined. [Objective] To study the correlation between intestinal flora diversity and depressive symptoms in patients with first-episode depression, and to analyze the potential relationship between intestinal flora diversity and Desulfovibrio and depression, thereby providing theoretical support for subsequent longitudinal studies. [Methods] The V4-V5 region fragments in the 16S rRNA gene from the feces of the depression group (n=23) and the normal group (n=31) were genetically sequenced, and the Hamilton Depression Scale was used to evaluate the two groups. The α diversity test, β diversity test, t-test, Pearson correlation test, and Spearman correlation test were used for statistical analysis. [Results] There was no significant difference in the diversity of intestinal flora between the depression group and the control group (P>0.05). There were differences in the structure of intestinal flora between the two groups. The relative abundances of 28 genera and 40 species were significantly different at genus and species levels (P<0.05). There was a significant positive correlation between intestinal flora diversity (Shannon index and Chao1 index) and depressive symptoms (P<0.05). In the correlation test of the relative abundances and depressive symptoms at genus and species levels, Desulfovibrio was significantly correlated with depressive symptoms (P<0.05). [Conclusion] In this study, there are differences existed in the structure and composition of intestinal microbiota between patients with first-episode depression and healthy people. There is a significant correlation between intestinal flora diversity and depressive symptoms, and there is a significant positive correlation between the relative abundances of some flora such as Desulfovibrio and the depressive symptoms.

Abstract:[Background] Malonyl-CoA:ACP transacylase (MCAT), an important subunit of type II fatty acid synthase (FASII), is associated with fatty acid synthesis. However, little information is available on microalgal MCAT. [Objective] To validate the function of the MCAT gene from Phaeodactylum tricornutum. [Methods] We found a possible mcat gene in the whole genome sequence of the model diatom P. tricornutum and cloned this gene. We performed bioinformatic analysis of this gene and introduced it into the MCAT-deficient E. coli L48 strain. Gas chromatography-mass spectrometry (GC-MS) was employed to analyze the composition and content of fatty acids in the mutant strains. [Results] The MCAT in P. tricornutum had the secondary structure mainly composed of α-helix and random coil and the closest genetic relationship with that in Fragilaria cylindrus, being a protits-type MCAT. To verify the function of the gene, we introduced this gene into the MCAT-deficient E. coli L48 strain and found that the strain recovered the function of fatty acid synthesis. Further, we analyzed the fatty acid composition of the reverting and found that the enzyme had a substrate preference to C14:0. The MCAT promoted the synthesis of medium- and long-chain fatty acids such as C16:0 and C17:1. This feature is largely consistent with the characteristics of protits-type MCATs. [Conclusion] There is a protits-type MCAT in P. tricornutum. This study provides new clues for the study of fatty acid synthesis and metabolism in microalgae, which is beneficial to the research and application of microalgal lipids.

Abstract:[Background] Iron in soil mainly exists in the form of insoluble iron oxide with low availability. The activation of iron oxide by siderophore-producing bacteria is an effective way to improve the iron utilization efficiency. [Objective] To observe the utilization of insoluble iron oxide by the siderophore-producing bacterial strains isolated from woodland soil and provide a theoretical basis for the development of microbial resources and the research on its role in nutrient regulation. [Methods] Siderophore-producing bacteria were isolated from surface soil near the tree roots by CAS detection method. The effects of temperature and pH on the growth and siderophore production of the isolates were analyzed by plate culture method. The activation effect of siderophore-producing bacteria on iron oxide was explored via oscillation balance experiments. [Results] Twelve siderophore-producing bacterial strains were isolated from surface soil near the tree roots. The results from 16S rRNA gene amplicon sequencing showed that the isolates were Pseudomonas. We selected two strains ARSB02 and CNRSB01 and analyzed their siderophore production and growth. The biomass and siderophore production of CNRSB01 were higher than those of ARSB02 under different conditions. At the time point of 22 h, the siderophore activity of ARSB02 and CNRSB01 reached 67.07% and 84.60%, respectively. The two strains could maintain good siderophore production within the range of pH 5.0-8.0 and the strongest siderophore production capacity (38.98% and 48.77%, respectively) at pH 7.0. The strains showed good siderophore production performance at 25-30℃ and the strongest siderophore production capacity (42.35% and 56.06%, respectively) at 30 ℃. Both ARSB02 and CNRSB01 grew well in goethite suspension. Strain ARSB02 had the highest biomass (OD₄₂₀value of 0.75) in the suspension with the iron oxide ratio of 0.03 g/L and strain CNRSB01 had the highest biomass (OD₄₂₀ value of 1.11) in the suspension with the iron oxide ratio of 0.015 g/L. The siderophore produced by the two strains could activate goethite. At the time point of 144 h, the activation of goethite by ARSB02 and CNRSB01 reached 12.99 μmol/L and 16.50 μmol/L, respectively. [Conclusion] The siderophore-producing bacteria isolated from surface soil near the tree roots all belong to Pseudomonas and have the ability to activate iron oxide. The results are of significance for the development and application of microbial resources in woodland soil.

Abstract:[Background] Bacillus amyloliquefaciens SQ-2 is a probiotic strain isolated from commercially available watercress paste, with previous experiments demonstrating its exceptional bacteriostatic ability against plant pathogenic fungi, indicative of strain SQ-2’s rather good bio-control abilities and potential application prospects in bio-pesticides. [Objective] To explore the genetic information of B. amyloliquefaciens SQ-2, and divulge its antifungal mechanism. [Methods] The whole-genome sequencing of strain SQ-2 was performed on an Illumina MiSeqX10 platform. Raw data were cleaned using Trim Galore v.0.4.0 and examined for quality using FastQC. In addition, de novo assembly was performed using the SOAPdenovo2 package. Genes responsible for the biosynthesis of secondary metabolites were identified using antiSMASH. [Results] The genome of B. amyloliquefaciens SQ-2 was 3 486 537 bp with the average guanine/cytosine (GC) content of 46.63%, which potentially coded 4298 genes. Eleven gene clusters related to secondary metabolite biosynthesis were discovered, of which six were identified as antifungal synthesis clusters, encoding bacillaene, bacilysin, butirosin, fengycin, bacillibactin, and surfactin, respectively. The sequencing data from this article were submitted to the NCBI and were available in the GenBank database (Login No. JAHXSB000000000). Ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis indicated that the surfactin, bacillibactin, and bacillaene were produced by strain SQ-2. [Conclusion] This study presents the genome sequence of B. amyloliquefaciens SQ-2, and it exhibits intense antagonistic activity against plant pathogenic fungi. The entirety of this genome sequencing study can assist in utilizing known antifungal peptides and searching for novel antifungal substances to combat pathogens.

Abstract:[Background] Microbial degradation of straw has attracted increasing attention of researchers. [Objective] To screen out the fungal strains with fast growth and strong activities of degrading lignin and cellulose for the efficient utilization of straw. [Methods] The fungal strains were isolated from the samples collected in the natural environments. PDA-guaiacol and PDA-carboxymethylcellulose were used for preliminary screening and then the activities of laccase and carboxymethyl cellulose (CMCase) of the selected strains were determined by liquid fermentation. The target strain was obtained by re-screening based on mycelial growth rate and identified by sequencing of internal transcribed spacer (ITS). Furthermore, the laccase and CMCase activites of the target strain was determined and the enzymatic properties were studied. [Results] A total of 18 strains of fungi were isolated from the samples, among which 9 strains producing lignocellulose-degrading enzymes were selected through preliminary screening. After re-screening, strain M1 with high activities of laccase and CMCase and fast mycelial growth was screened out as the target strain and identified as Pleurotus ostreatus. The strain had the laccase and CMCase activities of (243.59±1.11) U/mL and (36.03±0.63) U/mL, respectively, as well as the mycelial growth rate of (9.43±0.32) mm/d during the 5 days of culture. The relative activity of laccase produced by strain M1 was the most stable at pH 5.5 and over 90% in a pH range of 5.0 to 6.5 and below 55 ℃. The relative activity of CMCase produced by strain M1 was the most stable at pH 6.0 and over 90% in a pH range of 5.5 to 6.5 and below 60 ℃. [Conclusion] P. ostreatus M1 had high laccase and CMCase activities and the potential of degrading lignin and cellulose. This study provides a promising fungal strain for the biodegradation of straw.

Abstract:[Background] In agricultural ecosystems, the mechanisms of interactions between soil microorganisms and plants remain unclear. [Objective] To strengthen the understanding of plant-microorganism interactions and screen out the key microorganisms or microbial groups that cause different feedback effects. [Methods] The soil in the 0-20 cm layer of the fields domesticated with leguminous green manure Vicia sativa (V) or cruciferous green manure Brassica napus (N) and the remnant prairie (R) were collected as inoculants in the greenhouse for plant-soil feedback (PSF) test. Maize was planted in the substrate containing 10% inoculant and 90% sterilized soil with the same physical and chemical properties. The sterilized soil inoculum was set as the control (CK). For each inoculation treatment, two phosphorus levels, 50 mg/kg (high phosphorus, HP) and 5 mg/kg (low phosphorus, LP), were designed. After maize was harvested, we measured the yield and phosphorus content in the shoots and sequenced the soil samples to analyze feedback effects of microorganisms on crop growth under different nutrient supply conditions. [Results] High phosphorus and soil feedback both promoted the growth of maize. In the case of LP, the aboveground biomass of maize in the V, N, and R treatments all increased compared with that in the CK. Moreover, the increase in the N treatment (38%) was significantly higher than that in the V treatment (28%) and R treatment (16%). The V, N, and R treatments showed no significant difference in maize aboveground biomass compared with CK under the HP condition. The phosphorus content in the shoots of maize treated with the three soil inoculants was significantly higher than that of CK in the case of LP, while it showed no significant difference between treatments in the case of HP. There are differences in the composition of main species at each treatment phylum level, N treatment enriched more Proteobacteria and Bacteroidetes. KEGG pathway enrichment analysis showed that the abundance of functional genes phoB, phoA, phoR, phnA and glpR involved in phosphorus activation significantly increased in N treatment. [Conclusion] The soil microorganisms domesticated with cruciferous green manure could improve the phosphorus absorption ability and promote the growth of maize cruciferous green manure enriched more microorganisms and functional genes associated with phosphorus dissolution.

Abstract:[Background] Trichoderma sp. is an important biocontrol microorganism. Comparing the biological characteristics of different strains can provide information for multi-function biocontrol agent development. [Objective] To figure out the biological function differences among different strains by comparing and analyzing the preventive effects of Trichoderma virens T23 and the other two Trichoderma harzianum strains T22 and G30 and their biological characteristics. [Methods] Plate antagonism test was employed to compare the antagonistic effects of strains T23, T22, and G30 on plant pathogenic fungi. Gliotoxin was extracted from culture solution of strains T23, T22, and G30 by ethyl acetate extraction method and tested by high-performance liquid chromatography (HPLC). The antagonistic effects of the extracts on plant pathogenic fungi were compared by the hole drilling method, and the effects of strains T23, T22, and G30 on disease prevention were verified by plant inoculation in the greenhouse experiments. The conversion and utilization potential of strains T23, T22, and G30 to insoluble phosphorus was determined by using calcium phosphate and lecithin as the only phosphorus sources, respectively, and inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used for soluble phosphate detection. The main physiological and biochemical characteristics of strains T23, T22, and G30 were analyzed by the transparent ring method or chromogenic method. [Results] The plate antagonism rate of strains T23, T22, and G30 against Fusarium solani was 77%, 74%, and 48%, respectively, against Sclerotium rolfsii was 80%, 67%, and 24%, respectively, and against Botrytis cinerea was 93%, 62%, and 64% respectively. Neither strain T22 nor strain G30 carried gene clusters participating in gliotoxin biosynthesis, and no gliotoxin was detected in the culture solution of strains T22 and G30. The antibacterial rate of strain T23 extracts against S. rolfsii and B. cinerea was 40% and 65%, respectively. In the greenhouse experiment, strain T23 improved the emergence percentage (68%) of peanut seedlings under S. rolfsii stress and delayed the onset of disease in Rosa chinensis Jacq. for 16 days under B. cinerea stress. Strains T23 and T22 produced β-1,3-glucanase. Strains T23, T22, and G30 all possessed the ability to transform and utilize calcium phosphate. [Conclusion] Through comparative analysis, we have a further understanding of the disease prevention and growth-promoting effect of strain T23 and its physiological and biochemical characteristics. Strains T23, T22, and G30 have their characteristics and advantages in fungi antagonism and phosphorus solubilization. Strain T23 antagonizes pathogenic fungi by producing bacteriostatic natural products, which provides an important source for the development of fungus-derived biopesticides. In terms of growth promotion, the inorganic phosphorus solution mechanism of strain T23 needs to be further studied.

Abstract:[Background] Bacterial community plays an important role in soil nutrient cycling and meanwhile is affected by soil physical and chemical properties and crop yield. [Objective] To study the effects of co-application of polyacrylamide (PAM) and biochar on soil bacterial diversity and community structure, soil physical and chemical factors, and maize yield in Hetao irrigation area under drip irrigation. [Methods] We designed four treatments: control (CK, no polyacrylamide or biochar), 22.5 kg/hm² polyacrylamide+9 000 kg/hm² biochar (PB1), 22.5 kg/hm² polyacrylamide+ 13 500 kg/hm² biochar (PB2), and 22.5 kg/hm² polyacrylamide+18 000 kg/hm² biochar (PB3), to investigate the relationship among soil bacterial community, environmental factors, and maize yield by high-throughput sequencing technology. [Results] Compared with CK, PB1 and PB2 improved the alpha diversity indexes (Chao 1 and Shannon index) of soil bacteria. The co-application of polyacrylamide and biochar changed the structure of soil bacterial community, and the dominant groups of soil bacteria in different treatments were Proteobacteria and Subgroup_6. PB1 and PB2 significantly increased the content of available nitrogen and available potassium, respectively, and the comprehensive soil fertility was the highest in PB2 treatment. Redundancy analysis showed that pH was the main environmental factor affecting the bacterial community structure at the phylum and genus levels. The ear length, bald tip length, kernel number per row, and 100-kernel weight of maize in PB2 treatment were the highest. Actinobacteria, Subgroup_6, and RB41 played a positive role in increasing the kernel number per row, and Skermanella in increasing the ear length. [Conclusion] Under drip irrigation, co-application of polyacrylamide and biochar can directly or indirectly increase bacterial diversity and alter bacterial community structure by changing soil physical and chemical properties to improve maize yield, and PB2 treatment demonstrates the best performance.

Abstract:[Background] The soil-borne potato common scab (CS), caused by Streptomyces spp., is rampant in China, resulting in tremendous economic loss. With not efficient control measure available, the pathogen become more aggressive. Biocontrol bacteria which are environmentally friendly and show ideal effect in controlling the reproduction of the pathogen have attracted the interest of scholars. [Objective] To isolate and identify antagonistic bacterial isolate against Streptomyces scabies, determine the taxonomic status, evaluate the major biological traits, and thus to provide resources for the development of biocontrol agents. [Methods] Antagonistic isolates were screened from soil with high incidence of potato CS. The taxonomic status was confirmed with morphological, physiological, biochemical, and molecular methods. The control effect was analyzed by pot trials. Then, the potential application of the isolate was evaluated by broad-spectrum resistance (BSR) test, salt-alkali tolerance assay, and sensitivity tests to chemical fungicides. [Results] HD9-1 with significant antagonistic effect on S. scabies was screened out, which exhibited an inhibition zone diameter of 31 mm. The bacterial cells were rod-shaped and Gram-positive, with width of 0.75 μm and length of 1-2.5 μm. Colony of the isolate was yellowish, with smooth round edge. HD9-1 used sucrose as the only carbon source and produced β-galactosidase, arginine dihydrolase, lysine decarboxylase, and ornithine decarboxylase. IAA (3.44 mg/L) was detected in liquid medium after 24 h of culture. With the 16S rRNA sequence highly homologous to that of Bacillus subtilis RUB, HD9-1 was determined to be B. subtilis. The pot trial results showed that the scab-control efficiency was 59.15%. Under medium culture conditions, HD9-1 showed tolerance at pH 3.0-11.0, NaCl concentration of 1%-11%, and temperature of up to 100 °C (water bath for 30 min). This isolate was insensitive to zhongshengmycin, difenoconazole, fluconazole propamocarb, kasugamycin, flusilazole, pyrazole ether, azoxystrobin and thiophanate methyl. Meanwhile, it showed certain control effect on other crop pathogens, such as Verticillium dahliae, Fusarium oxysporum, and Rhizoctonia solani. [Conclusion] HD9-1, a B. subtilis strain, displays significant control effect on potato CS and strong adaptability, which can be a potential candidate for developing compound microbial agent against some potato soil-borne diseases.

Abstract:[Background] Mycobacterium bovis, a major zoonotic pathogen, seriously endangers public health. Macrophages are the main effector cells of M. bovis infection. The polarization of macrophages into M1 type is of great significant for the host immune defense against M. bovis infection. [Objective] To explore the effect of guanylate-binding protein 5 (GBP5) on the M1/M2 polarization of mouse mononuclear macrophage RAW264.7 cells infected with M. bovis, and reveal the role of GBP5 in M. bovis infection. [Methods] GBP5 was screened out as differentially expressed gene by preliminary transcriptomic data analysis. The increased expression level of GBP5 after M. bovis infection was verified in vivo and in vitro. The expression of GBP5 was down-regulated in the cells by siRNA, and then the surface markers of M1 and M2 macrophages were detected by RT-qPCR, Western blotting, and flow cytometry. The effect of GBP5 on M. bovis replication in macrophages was examined via plate colony counting method. The regulation of signal transducer and activator of transcription 3 (STAT3) transcription by GBP5 was verified by dual-luciferase reporter system. Phosphorylation of STAT3 was detected by Western blotting after inhibition on the release of reactive oxygen species. [Results] The expression of GBP5 was up-regulated in RAW264.7 cells and C57BL/6 mouse tissue after M. bovis infection. The down-regulation of GBP5 expression significantly increased the intracellular colony forming units (CFU) of M. bovis at different time points, reduced the release of ROS, and inhibited the surface markers of M1 macrophages. Otherwise, it exerted no significant effect on M2 macrophages. In addition, the down-regulation of GBP5 inhibited the transcription of STAT3. ROS production inhibited the phosphorylation of STAT3. [Conclusion] GBP5 can promote ROS production and regulate ROS/STAT3 pathway to promote the polarization of macrophages into M1 type, thereby inhibiting the survival of M. bovis in cells.

Abstract:[Background] Dihydromyricetin (DMY) is a major flavonoid compound in Vine tea (Ampelopsis grossedentata), which has antioxidant, anti-inflammatory, and other effects. Its medicinal value has attracted extensive attention, but its biological activity in vivo and catabolic mechanism in intestine are still unclear. [Objective] To explore the effects of dihydromyricetin on serum antioxidant capacity and intestinal microbial diversity of mice under antibiotic stress. [Methods] The experimental mice were divided into a control group, an antibiotic group, and an antibiotic+dihydromyricetin group. The antioxidant indexes in the serum of mice in each group were detected. The differences of intestinal microbial diversity between groups were analyzed by high-throughput sequencing. The relative abundance differences between specific bacterial groups were verified by real time fluorescence quantitative polymerase chain reaction (RT-qPCR). [Results] Dihydromyricetin significantly increased the activities of catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) in the serum of antibiotic stressed mice (P<0.05), significantly decreased the content of malondialdehyde (MDA) (P<0.05), catalyzed the synthesis of nitric oxide (NO), and significantly increased the total antioxidant capacity of mice. There were significant differences in the composition and structure of intestinal microorganisms between the antibiotic+dihydromyricetin group and the antibiotic group. Dihydromyricetin improved the composition of intestinal flora in mice by regulating the abundance ratio of Firmicutes and Bacteroidetes, promoting the proliferation of bacteria such as Lactobacillus and Clostridium, and inhibiting the proliferation of Enterobacteriaceae, so as to increase the relative abundance of beneficial bacteria related to intestinal catabolism such as Lactobacillus and Clostridium in the intestinal tract of mice. [Conclusion] Dihydromyricetin can change the structure of intestinal flora. Some probiotics are heavily involved in its metabolic process and produce beneficial metabolites to improve the antioxidant capacity of the body and maintain intestinal health. Negative effects of antibiotics on the intestinal tract of mice are thus reduced. These findings provide a theoretical basis for the study of the function and catabolic mechanism of dihydromyricetin.

Abstract:[Background] Calcimycin is an essential ionophoric antibiotic. The gene cluster for calcimycin biosynthesis has been cloned from the genome of Streptomyces chartreusis NRRL3882, but functions of some biosynthetic genes and regulatory genes in calcimycin biosynthesis remain unclear. [Objective] To study the functions of the putative regulatory gene calR1 encoding TylR-family transcriptional regulator in the biosynthetic gene cluster of calcimycin. [Methods] ThecalR1-knockout mutant and complementary strain were constructed by PCR-targeting and fermented, and their metabolites were analyzed by HPLC. The transcriptions of biosynthetic genes in ΔcalR1 mutant and wild-type strain were analyzed by RT-qPCR. [Results] ΔcalR1 mutant lost the ability to produce calcimycin, while the accumulation of cezomycin was observed. The complementary strain restored the production of calcimyc into a certain degree. The transcriptions of some essential genes, including calC, calG, and calU3, were substantially changed in ΔcalR1 mutant compared with those in the wild-type strain. [Conclusion] The putative TylR-family transcription regulatory gene calR1 is involved in calcimycin biosynthesis.

Abstract:[Background] Proteases can degrade the misfolded or nonfunctional proteins in cells. Clp family protein is one of the important protease complexes. ClpP is the core of proteolysis of Clp protease complex. According to genomic data, there are four different ClpP proteins in Synechocystis sp. PCC6803, namely ClpP1–ClpP4. As a vital functional component of proteolytic complex, ClpP in Synechocystis is currently poorly studied. The study on its physiological function and substrate regulation is limited. [Objective] To explore the functions of ClpP2 in Synechocystis and identify potential substrate clusters, thereby providing experimental support for the mechanism research of ClpP2. [Methods] The ClpP2 mutant strain (ΔClpP2) was constructed, and the growth experiment and photosynthetic system characteristic experiment were carried out. Target proteins regulated by ΔClpP2 were identified by isobaric tag for relative absolute quantitation (iTRAQ), and the metabolic pathways involved in the substrate proteins were analyzed via bioinformatics. Finally, parallel reaction monitoring (PRM) was used to verify part of the quantitative data. [Results]ΔClpP2 grew into the logarithmic phase through photoautotrophy under natural conditions, but did not grow normally when met high-light or high-temperature stress. Compared with the wild-type (WT), ΔClpP2 showed significantly reduced photosystem Ⅱ (PSⅡ) electron transport efficiency and circle electron transport activity of photosystemⅠ(PSⅠ). A total of 206 differentially expressed proteins in ΔClpP2 were identified by iTRAQ quantitative proteomics. Among them, 131 were up-regulated and 74 were down-regulated, which provided a rich substrate library. Gene Ontology (GO) analysis showed that ClpP2 was mainly involved in the transport of various substances, and ABC transporter pathway was enriched notably. Thirty-four differentially expressed proteins were successfully verified by PRM technology. [Conclusion] ClpP2 is not necessary for the growth of Synechocystis, but is essential when Synechocystis meets high-temperature or high-light stress. ClpP2 inactivation reduces the activity of the photosynthetic system in Synechocystis. ClpP2 might affect the photosynthetic system by regulating ion transport. ClpP2 is likely to bind with ClpX to form a protease complex.

Abstract:[Background] Assembling large DNA fragments is crucial in genome synthesis. Exploring inexpensive and efficient DNA assembly technologies has been a research hotspot in synthetic biology. In some bacteria such as Streptomyces lividans, there exists phosphorothioation modification on DNA (also known as DNA sulfur modification), while in some other bacteria such as Streptomyces coelicolor, there is a protein possessing sulfur-binding domain (SBD), which serves as a reader protein to specifically recognize the sulfur modification on DNA. This inspired us to develop a new technology to ligate long DNA fragments. [Objective] In this study, we introduced sulfur modification at the 5′ and 3′ ends of the DNA fragments to be ligated, and employed a fusion protein containing SBD domain and T4 DNA ligase to complete the ligation of long DNA fragments in vitro and compare the different efficiency between 2.5 kb and 8 kb fragments with these two ligases. [Methods] We designed sulfur-modified primers and amplified 2.5 kb and 8 kb DNA fragments with sulfur modification. Additionally, we constructed three fusion protein vectors: T4-linker-SBD (Hga), T4-linker-SBD (Spr), and T4-linker-SBD (Mmo) and expressed them in Escherichia coli and compared the ligation efficiency between T4 DNA ligase and fusion proteins under three different concentration gradients: 2.4, 0.24, 0.024 mg/mL. [Results] We successfully amplified 2.5 kb and 8 kb DNA fragments with sulfur modification and expressed these three fusion proteins. In the 2.5 kb DNA fragments ligation experiment, we found that T4 DNA ligase and fusion protein under the three concentration gradients and in twelve groups all successfully ligated, whereas in the 8 kb DNA fragments ligation experiment, only T4-linker-SBD (Hga) fusion protein successfully ligated two 8 kb fragments into 16 kb fragment. [Conclusion] According to our agarose gel electrophoresis, we concluded that in the 8 kb DNA fragments ligation experiment, T4-linker-SBD (Hga) fusion protein had higher ligation efficiency. Thus our method provide a new way to assemble large DNA fragments with low cost and high efficiency.

Abstract:[Background] Since the human infection with avian influenza that occurred in Hong Kong in 1997, avian influenza virus has become a major threat to human health and public health. [Objective] To perform the molecular epidemiological study on a human infection with H10N3 avian influenza. [Methods] Influenza virus subtyping was detected by real-time quantitative polymerase chain reaction (PCR) method. The virus genome sequencing was completed on the next-generation sequencing platform. Bioinformatics software such as Blasts and Mega 6.1 was used for sequence and phylogenetic analysis. [Results] In April 2021, a virus was isolated from patients with severe respiratory diseases, which was confirmed as H10N3 subtype avian influenza virus by nucleic acid detection and sequence analysis. A H10N3 subtype avian influenza virus was isolated from the farm product market near the patient’s residence, which was highly homologous with the human isolate. The human isolate was a new gene recombinant H10N3 avian influenza virus, and its HA and NA combination first appeared in poultry in East China in 2019. However, its six internal genes came from H9N2 virus prevalent in poultry in southern China in recent years. The HA cleavage site of the virus contained one basic amino acid R, without insertion of multiple basic amino acids. In theory, it did not belong to highly pathogenic avian influenza virus. The amino acid residue at 228 of HA receptor binding site mutated from G to S, which theoretically enhanced the affinity with human SA-α-2,6 receptor. No E627K mutation of PB2 protein was found, but the amino acid residue at site 591 mutated from Q to K, which theoretically enhanced the adaptability to human body and the pathogenicity. [Conclusion] This paper reported the molecular epidemiological characteristics of a case of human infection with H10N3 avian influenza virus, and revealed that live poultry market played an important role in gene recombination of avian influenza virus and opportunistic infection.

Abstract:Truffle is a precious underground fungus famous all over the world for its unique aroma and taste and has economic, medicinal, and ecological values. Truffles form ectomycorrhiza with host plants before forming fruiting bodies (ascocarps). Considering the high economic value and the serious destruction of wild resources, artificial cultivation imitating wild truffle growth by preparation of seedlings with truffle mycorrhiza has received extensive attention. Focusing on the cultivation of seedlings with truffle mycorrhiza, we elaborated on the threats to truffle resources, the progress in artificial cultivation methods, and the rapid development of plantations. Furthermore, we summarized the research progress in the selection of symbiotic combinations, substrates, inoculants, culture methods, interaction with other organisms, and methods of identification. This review will provide a reference for developing the methods for cultivating seedlings with mycorrhiza and promoting artificial cultivation of mycorrhizal edible fungi.

Abstract:Ochratoxin A (OTA) is a secondary metabolite of fungi such as Aspergillus and Penicillium, which contaminated a variety of agricultural products and feeds such as grain, grapes, and nuts, causing serious economic losses. Moreover, increasing studies have demonstrated the liver and kidney toxicity as well as the teratogenicity, carcinogenicity, and mutagenesis of OTA, which poses a huge threat to human health. Although OTA and its derivatives have been studied comprehensively in terms of physicochemical properties, the synthesis process and regulatory mechanism of them remain unclear. This paper introduced the physicochemical properties and toxin-producing strains of OTA, reviewed the latest research progress in OTA contamination and pathogenic conditions, summarized the limit standards of different countries, expounded the synthesis mechanism of OTA, and finally discussed the future research directions. With this paper, we hope to provide data support for the risk assessment of OTA and provide theoretical reference for the research on the biosynthesis and regulatory mechanism of OTA.

Abstract:Potato scab, a soil-borne bacterial disease that exists worldwide, is difficult to control. The phytotoxin thaxtomins, produced by the secondary metabolism of Streptomyces scabies, are the main cause of potato scab, and result in serious damage to potato and other crop industries. Due to the serious impact of S. scabies on agriculture, the biosynthesis and molecular regulation of thaxtomins have attracted many attentions and made great progress. This article reviewed the structural characteristics, biosynthesis, and heterologous expression of thaxtomins, focusing on the molecular regulatory mechanism of thaxtomins biosynthesis in S. scabies. This review helps deeply understand the regulatory network of the secondary metabolism of S. scabies, and provides theoretical guidance for the development of new control strategies for potato scab in the future.

Abstract:AA10 lytic polysaccharide monooxygenases (LPMOs) mainly exist in bacteria. They have great application potential in industrial biomass conversion because of the ability in degrading crystalline polysaccharides such as cellulose and chitin and thus have attracted wide attention. However, the substrates, oxidation sites, and oxidation products vary among different AA10 LPMOs, and the influence mechanism of the structure and composition of LPMOs on the substrate selectivity remains to be explored. This paper introduced the modular structure, catalytic mechanism, and substrate spectrum of AA10 LPMOs. Further, we reviewed the research progress in the effects of structure, critical functional residues, and module combination of AA10 LPMOs on substrate selectivity. On this basis, we put forward the application prospects of LPMOs in biomass conversion and biofuel industry.

Abstract:ε-poly-l-lysine (ε-PL) is a natural antibacterial agent with a wide range of bacteriostatic spectrum. It is synthesized by the polymerization of 25 to 35 lysines linked by α-carboxyl group and ε-amino group. ε-PL is mainly produced by the fermentation of Streptomyces albulus, which is more efficient and environmentally friendly than chemical production. ε-PL has many excellent properties, such as good water solubility, heat resistance, edibility and nontoxicity to the environment, and has good application prospects. In this paper, the research progress of ε-PL on the bacteriostatic properties, bacteriostatic mechanisms, and bacteriostatic mechanism models of various microorganisms were reviewed. It was speculated that ε-PL may affect the expression of regulatory genes by destroying the cell membrane, changing the permeability of cells, or acting on the cells to cause the stress of reactive oxygen (ROS), so as to play an antibacterial role. According to these two bacteriostatic methods, corresponding bacteriostatic models were established, respectively, namely the carpet model and the ROS-induced apoptosis model. This study provides references for the further study of ε-PL on microbial inhibition, and also puts forward a new model of ε-PL antibacterial mechanism, thus providing certain references for expanding the application field of ε-PL.

Abstract:With the main constituents of polysaccharides and proteins, microalgal extracellular polymers substances (EPS) feature unique structure, large specific surface area, and a large number of functional groups, playing a very important role in wastewater treatment and flocculation for recovering microalgal biomass. In this paper, we introduce the composition and characteristics of EPS, focusing on the biotic factors and abiotic factors that affect the production of EPS, such as light, nutrients, pH, and temperature. The application of EPS in wastewater treatment and bioflocculation is summarized. The in-depth research on the production mechanism of microalgal EPS is expected to expand the application of microalgae.

Abstract:Young teachers are the backbone of talent training in colleges and universities, and their teaching ability is directly associated with the quality of talent training and the implementation of the fundamental task of moral cultivation. To improve the teaching ability of young teachers, the microbiology teaching team of Huazhong Agricultural University created a team chain method according to the requirement of promoting the all-round development of morality, intelligence, physique, aesthetics, and labor, and innovated the teaching idea with a mode of “double teams and double mentors”. With this method, two first-class courses and a Hubei provincial teaching team of Microbiology were developed, and a paradigm platform for the practice of teaching ability improvement was built. Adhering to the original aspiration of teaching and education, we are committed to cultivating new talents of the times for the rejuvenation of the Chinese nation.

Abstract:In years of blended teaching of Microbiology Experiment, we found that students' initiative is the key to the learning effect. In the past, some students were passive in spite of diverse teaching methods applied. In recent years, we have adopted the task-driven teaching method: responsibility system of team leader rotation, which has remarkably incentivized all the students. As a team leader, each student has played an important role in pre-class tasks, the implementation in class, and summarization after class. In addition, they actively cooperated with the team leader when not serving as the team leader. Finally, the proportion of students achieving excellent results in the course and the marks on the quality and ability were significantly improved. Moreover, this method has been recognized by the students.

Abstract:There are two problems in the traditional teaching of microbiology. First, the teaching cannot meet the diverse and individualized needs of students. Second, the students lack motivation and interest in learning because of their vague ambition and the abstruse nature of microbiology. To solve these problems, the microbiology teaching team adopted student-centered and output-oriented strategy to innovate the teaching method. Specifically, the team helped students establish faith, serve our country, and revitalize the rural area in a way that enabled then to find their sparks and plan of life. The teaching design was also innovated, which consisted of self-study before class, discussion in class, and practice after class, achieving seamless docking between online and offline teaching. Moreover, innovative measures were implemented according to innovation requirements, high-level standards, and challenge degrees, including perception after each class, experience and extended learning. These measures developed sufficient teacher-student and student-student interactions. Meanwhile, curriculum ideological and political education was designed to run through the teaching process. Finally, a multiple evaluation system was formed for the innovative teaching. Students were satisfied with this reform, demonstrating significantly improved participation rate of entrepreneurship and innovation projects, admission rate for postgraduate entrance, academic performance, and discipline competition achievement. The results can provide references for innovative reform of microbiology teaching.