The three parts(Stx17B, Stx27B and StxB) of Shiga toxin B subunit have been fused into a cell surface exposed loop of the LamB protein at a BamH I site between residues 153 and 154. Western blotting revealed that the ...The three parts(Stx17B, Stx27B and StxB) of Shiga toxin B subunit have been fused into a cell surface exposed loop of the LamB protein at a BamH I site between residues 153 and 154. Western blotting revealed that the three parts of Shiga toxin B subunit could be expressed as the Lamb fusion proteins in E. coli. Indirect immunofluorescence and immunoelectron microscopy analyses showed fusion proteins LamB/Stx17B and LamB/Stx27B could be expressed at cell surface in E. coli, but fusion protein LamB/StxB could not be expressed at cell surface; it was aggregated in cytoplasm and was toxic to host. This expression system provided a new way to construct an oral live vaccine against Shigella dysenteriae 1.展开更多
应用多样性增量结合二次判别分析(Increment of Diversity with Quadratic Discriminant analysis,IDQD)方法,对大肠杆菌σ70启动子进行识别。使用受试者操作特性(receiver operating characteristic,ROC)曲线和精度召回率曲线(Precisio...应用多样性增量结合二次判别分析(Increment of Diversity with Quadratic Discriminant analysis,IDQD)方法,对大肠杆菌σ70启动子进行识别。使用受试者操作特性(receiver operating characteristic,ROC)曲线和精度召回率曲线(Precision Recall Curves,PRC)进行性能评估。10-fold交叉检验给出,在正负集之比为1∶1时,ROC曲线下面积和PRC曲线下面积均为95%。结果表明,IDQD算法有能力应用于原核启动子的识别。识别精度高于现有算法。展开更多
本文采用水热法制备了甲壳素(Chitin)和石墨相氮化碳(g-C3N4)复合材料Chitin-CN,并采用XRD、SEM、XPS、光电流及阻抗分析等手段对其进行物化特性分析.与g-C3N4相比,Chitin-CN复合材料的光生电子-空穴对的分离效率较高,甲壳素(Chitin)含...本文采用水热法制备了甲壳素(Chitin)和石墨相氮化碳(g-C3N4)复合材料Chitin-CN,并采用XRD、SEM、XPS、光电流及阻抗分析等手段对其进行物化特性分析.与g-C3N4相比,Chitin-CN复合材料的光生电子-空穴对的分离效率较高,甲壳素(Chitin)含量为0.2 g的Chitin-CN材料在模拟太阳光照射下对大肠杆菌K-12表现出最佳的光催化杀菌效率,在2 h内可完全杀死6.5 lg cfu·mL-1的大肠杆菌K-12.Chitin-CN的破碎结构暴露了更多的活性位点,甲壳素的加入提高了光生载流子的分离率,从而促进了复合材料光催化杀菌的性能.捕获实验表明超氧自由基(·O-2)和空穴(h+)是Chitin-CN作用于大肠杆菌K-12的主要活性物种.展开更多
In the present paper it is rcported that glycolipid was successfully inserted into colorchangeable TCDA/DGG and PCDA/DGG polydiacetylene vesicles based on physical force rather than covalent binding. And the effects o...In the present paper it is rcported that glycolipid was successfully inserted into colorchangeable TCDA/DGG and PCDA/DGG polydiacetylene vesicles based on physical force rather than covalent binding. And the effects on polyinerization of diacetylene and the change of the polymer vesicles’ color due to the relative quantity of glycolipid versus diacctylene molecules were also reported. The experimental results demonstrated that this approach is available and the colorchangeable property of such polydiacetylenic vesicles was not affected due to the inceorporation of glycolipid. This provided a simple and useful method of functonalizing the polymer vesicles for their wide applications.展开更多
Lacto-N-neotetraose(LNnT),one of the most important human milk oligosaccharides,can be used as infants’food addi-tives.Nowadays,extraction,chemical and biological synthesis were utilized to obtain LNnT,while these me...Lacto-N-neotetraose(LNnT),one of the most important human milk oligosaccharides,can be used as infants’food addi-tives.Nowadays,extraction,chemical and biological synthesis were utilized to obtain LNnT,while these methods still face some problems such as low yield and high cost.The aim of current work is to construct a de novo biosynthesis pathway of LNnT in E.coli K12 MG1655.The lgtA and lgtB were first expressed by a plasmid,resulting in a LNnT titer of 0.04 g/L.To improve the yield of LNnT on substrate lactose,lacZ and lacI were knocked out,and lacY was over-expressed.As a result,the yield of LNnT on lactose increased from 0.01 to 0.09 mol/mol,and the titer of LNnT elevated to 0.41 g/L.In addition,the pathway was regulated using the titer of Lacto-N-triose II(LNTII)as a measure,and obtained a high titer strain of LNnT for 1.04 g/L.Finally,the gene expressions were fine-tuned,the titer of LNnT reached 1.2 g/L,which was 93%higher than the control strain,and the yield on lactose reached 0.28 mol/mol.The engineering strategy of pathway construction and modulation used in this study is applicable to facilitate the microbial production of other metabolites in E.coli.展开更多
Nodulation is the predominant cellular defense reaction to bacterial challenges in insects. In this study, third instar larvae of Chrysomya megacephala were injected with bacteria, Escherichia coli K 12 （10^6 CFU/mL...Nodulation is the predominant cellular defense reaction to bacterial challenges in insects. In this study, third instar larvae of Chrysomya megacephala were injected with bacteria, Escherichia coli K 12 （10^6 CFU/mL, 2μL）, immediately prior to injection of inhibitors of eicosanoid biosynthesis, which sharply reduced nodulation response. Test larvae were treated with specific inhibitors ofphospholipase A2 （dexamethasone）, cyclo- oxygenase （indomethacin, ibuprofen and piroxicam）, dual cyclo-oxygenase/lipoxygenase （phenidone） and lipoxygenase （esculetin） and these reduced nodulation except esculetin. The influence of bacteria was obvious within 2 h of injection （5 nodules/larva）, and increased to a maximum after 8 h （with 15 nodules/larva）, and then significantly reduced over 24 h （9 nodules/larva）. The inhibitory influence of dexamethasone was apparent within 2 h of injection （4 vs. 5 nodules/larva）, and nodulation was significantly reduced, compared to control, over 24 h （5 vs. 8 nodules/larva）. Increased dosages of ibuprofen, indomethacin, piroxicam and phenidone led to decreased numbers of nodules. Nodules continued to exist during the pupal stage. However, the effects of dexamethasone were reversed by treating bacteria-injected insects with an eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. These findings approved our view that eicosanoid can mediate cellular defense mechanisms in response to bacterial infections in another Dipteran insect C. rnegacephala.展开更多
Gram-negative bacteria have become the main pathogens and cause serious clinical problems with increased morbidity and mortality. However, the slow discovery of new antimicrobial agents is unable to meet the need for ...Gram-negative bacteria have become the main pathogens and cause serious clinical problems with increased morbidity and mortality. However, the slow discovery of new antimicrobial agents is unable to meet the need for the treatment of bacterial infections caused by drug-resistant strains. The interaction of L12 and L10 is essential for ribosomal function and protein synthesis. In this study, a yeast two-hybrid system was established to successfully detect the interaction between L12 and L10 proteins from gram-negative bacteria Escherichia coli, which allows us to screen compounds that specifically disrupt this interaction. With this system, we identified two compounds IMB-84 and IMB-87 that block L12-L10 interaction and show bactericidal activity against E. coli. We used glutathione-S-transferase(GST) pull-down and surface plasmon resonance(SPR) assays to demonstrate that these compounds disrupt L12-L10 interaction in vitro and the target of compounds was further confirmed by the overexpression of target proteins. Moreover, protein synthesis and elongation factor G-dependent GTPase activities are inhibited by two compounds. Therefore, we have identified two antibacterial agents that disrupt L12-L10 interaction by using yeast two-hybrid system.展开更多
文摘The three parts(Stx17B, Stx27B and StxB) of Shiga toxin B subunit have been fused into a cell surface exposed loop of the LamB protein at a BamH I site between residues 153 and 154. Western blotting revealed that the three parts of Shiga toxin B subunit could be expressed as the Lamb fusion proteins in E. coli. Indirect immunofluorescence and immunoelectron microscopy analyses showed fusion proteins LamB/Stx17B and LamB/Stx27B could be expressed at cell surface in E. coli, but fusion protein LamB/StxB could not be expressed at cell surface; it was aggregated in cytoplasm and was toxic to host. This expression system provided a new way to construct an oral live vaccine against Shigella dysenteriae 1.
文摘本文采用水热法制备了甲壳素(Chitin)和石墨相氮化碳(g-C3N4)复合材料Chitin-CN,并采用XRD、SEM、XPS、光电流及阻抗分析等手段对其进行物化特性分析.与g-C3N4相比,Chitin-CN复合材料的光生电子-空穴对的分离效率较高,甲壳素(Chitin)含量为0.2 g的Chitin-CN材料在模拟太阳光照射下对大肠杆菌K-12表现出最佳的光催化杀菌效率,在2 h内可完全杀死6.5 lg cfu·mL-1的大肠杆菌K-12.Chitin-CN的破碎结构暴露了更多的活性位点,甲壳素的加入提高了光生载流子的分离率,从而促进了复合材料光催化杀菌的性能.捕获实验表明超氧自由基(·O-2)和空穴(h+)是Chitin-CN作用于大肠杆菌K-12的主要活性物种.
文摘In the present paper it is rcported that glycolipid was successfully inserted into colorchangeable TCDA/DGG and PCDA/DGG polydiacetylene vesicles based on physical force rather than covalent binding. And the effects on polyinerization of diacetylene and the change of the polymer vesicles’ color due to the relative quantity of glycolipid versus diacctylene molecules were also reported. The experimental results demonstrated that this approach is available and the colorchangeable property of such polydiacetylenic vesicles was not affected due to the inceorporation of glycolipid. This provided a simple and useful method of functonalizing the polymer vesicles for their wide applications.
基金This work was supported by the National Natural Science Foundation of China(31930085,32021005)the key research and development program of China(2018YFA0900300,2020YFA0908300).
文摘Lacto-N-neotetraose(LNnT),one of the most important human milk oligosaccharides,can be used as infants’food addi-tives.Nowadays,extraction,chemical and biological synthesis were utilized to obtain LNnT,while these methods still face some problems such as low yield and high cost.The aim of current work is to construct a de novo biosynthesis pathway of LNnT in E.coli K12 MG1655.The lgtA and lgtB were first expressed by a plasmid,resulting in a LNnT titer of 0.04 g/L.To improve the yield of LNnT on substrate lactose,lacZ and lacI were knocked out,and lacY was over-expressed.As a result,the yield of LNnT on lactose increased from 0.01 to 0.09 mol/mol,and the titer of LNnT elevated to 0.41 g/L.In addition,the pathway was regulated using the titer of Lacto-N-triose II(LNTII)as a measure,and obtained a high titer strain of LNnT for 1.04 g/L.Finally,the gene expressions were fine-tuned,the titer of LNnT reached 1.2 g/L,which was 93%higher than the control strain,and the yield on lactose reached 0.28 mol/mol.The engineering strategy of pathway construction and modulation used in this study is applicable to facilitate the microbial production of other metabolites in E.coli.
文摘Nodulation is the predominant cellular defense reaction to bacterial challenges in insects. In this study, third instar larvae of Chrysomya megacephala were injected with bacteria, Escherichia coli K 12 （10^6 CFU/mL, 2μL）, immediately prior to injection of inhibitors of eicosanoid biosynthesis, which sharply reduced nodulation response. Test larvae were treated with specific inhibitors ofphospholipase A2 （dexamethasone）, cyclo- oxygenase （indomethacin, ibuprofen and piroxicam）, dual cyclo-oxygenase/lipoxygenase （phenidone） and lipoxygenase （esculetin） and these reduced nodulation except esculetin. The influence of bacteria was obvious within 2 h of injection （5 nodules/larva）, and increased to a maximum after 8 h （with 15 nodules/larva）, and then significantly reduced over 24 h （9 nodules/larva）. The inhibitory influence of dexamethasone was apparent within 2 h of injection （4 vs. 5 nodules/larva）, and nodulation was significantly reduced, compared to control, over 24 h （5 vs. 8 nodules/larva）. Increased dosages of ibuprofen, indomethacin, piroxicam and phenidone led to decreased numbers of nodules. Nodules continued to exist during the pupal stage. However, the effects of dexamethasone were reversed by treating bacteria-injected insects with an eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. These findings approved our view that eicosanoid can mediate cellular defense mechanisms in response to bacterial infections in another Dipteran insect C. rnegacephala.
基金supported by the National Natural Science Foundation of China (Grant nos.81370089,81529003,81621064 and 81361138020)the Foundation for Innovative Research Groups and the Funds for International Cooperation and Exchange between China–Sweden and CAMS Initiative for Innovative Medicine (2016-12M-3-014)
文摘Gram-negative bacteria have become the main pathogens and cause serious clinical problems with increased morbidity and mortality. However, the slow discovery of new antimicrobial agents is unable to meet the need for the treatment of bacterial infections caused by drug-resistant strains. The interaction of L12 and L10 is essential for ribosomal function and protein synthesis. In this study, a yeast two-hybrid system was established to successfully detect the interaction between L12 and L10 proteins from gram-negative bacteria Escherichia coli, which allows us to screen compounds that specifically disrupt this interaction. With this system, we identified two compounds IMB-84 and IMB-87 that block L12-L10 interaction and show bactericidal activity against E. coli. We used glutathione-S-transferase(GST) pull-down and surface plasmon resonance(SPR) assays to demonstrate that these compounds disrupt L12-L10 interaction in vitro and the target of compounds was further confirmed by the overexpression of target proteins. Moreover, protein synthesis and elongation factor G-dependent GTPase activities are inhibited by two compounds. Therefore, we have identified two antibacterial agents that disrupt L12-L10 interaction by using yeast two-hybrid system.
