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Search Results: 1 - 10 of 127101 matches for " Jilun Li "
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Hydrogen metabolic pathways of Rhodospirillum rubrum under artificial illumination
RuiYan Zhu,JiLun Li
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-009-0706-1
Abstract: Multiple enzymes involved in hydrogen metabolism have been detected in photosynthetic bacterium Rhodospirillum rubrum under various growth conditions. To investigate hydrogen metabolic pathways and the contribution of each pathway to hydrogen photoproduction in R. rubrum under the artificial illumination condition, three mutants were constructed, including nifHanfDG double mutant lacking both Fe-nitrogenase and Mo-nitrogenase, anfDG mutant lacking Fe-nitrogenase and nifHhupL double mutant (uptake hydrogenase deficient mutant). Comparison of the hydrogen production of these 3 mutants with R. rubrum wild type and the uptake hydrogenase deficient mutant showed that there was a third pathway involved in hydrogen production besides Mo-nitrogenase and Fe-nitrogenase, which mainly contributed to hydrogen evolution. Only a small portion of hydrogen was generated by the third pathway. The hydrogen produced by Mo-nitrogenase, Fe-nitrogenase and the third pathway was about 93.5%, 4.9% and 1.5%, respectively, while the hydrogen consumed by uptake hydrogenase was about 13.3%. The investigation of the formate-linked hydrogenase activity indicated that the third pathway for hydrogen production was not mediated by the formate-linked hydrogenase, but probably by some unknown enzyme.
Construction and characterization of double mutants in nitrogenase ofKlebsiella pneumoniae
Dehua Zhao,Jilun Li
Chinese Science Bulletin , 2004, DOI: 10.1007/BF03184303
Abstract: Two mutants in nitrogenase ofKlebsiella pneumoniae are constructed by site-directed mutagenesis and gene replacement procedure, which express the nitrogenases with Lysine and Glutamine substituting for α-Glutamine 190 and α-Histidine 194 respectively (Kp-Q α190 K and Kp-H α194 Q). The above two substitutions are respectively introduced into anifV mutant (expressing a citrate-containing nitrogenase) and sequentially two double mutants are obtained (Kp-Q α190 K-nifV and Kp-H α194 Q-nifV ). All four mutants exhibit strict Nif-phenotype under the N2-fixation condition and fail to grow diazotrophically. Altered nitrogneases are effectively depressed and the C2H2 reduction analysis shows that the double substitutions in Kp-Q α190 K-nifV abolish cell C2H2 reduction activity, but Kp-H α194 Q-nifV cells maintain a C2H2 reduction activity at 10% of that of wild type. Whole cell C2D2 reduction by all four mutants in comparison to the wild type andnifV mutant is also detected. The results show that only single α-Gln194 substitution does not perturb the stereospecificity of protonation of C2D2. These results indicate that the α-Glutamine 190 and its combination with homocitrate are essential to the catalytic activity of nitrogenase and it is proposed that α-Glutamine 190 and its combination with homocitrate are involved in the proton and/or electron transfer to FeMoco. The nitrogenases from these double mutants will be useful in further analysis of the entry of the proton and/or electron to FeMoco and the substrate binding sites.
Hydrogen metabolic pathways of Rhodospirillum rubrum under artificial illumination

RuiYan Zhu,JiLun Li,

科学通报(英文版) , 2010,
Abstract: Multiple enzymes involved in hydrogen metabolism have been detected in photosynthetic bacterium Rhodospirillum rubrum un-der various growth conditions. To investigate hydrogen metabolic pathways and the contribution of each pathway to hydrogen photoproduction in R. rubrum under the artificial illumination condition, three mutants were constructed, including nifHanfDG double mutant lacking both Fe-nitrogenase and Mo-nitrogenase, anfDG mutant lacking Fe-nitrogenase and nifHhupL double mu-tant (uptake hydrogen...
Interaction between GlnB and the N-terminal domain of NifA in Azospirillum brasilense
XiaoYu Zhou,XiaoXiao Zou,JiLun Li
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0435-x
Abstract: Azospirillum brasilense is a diazotroph associated with many important agricultural crops and shows potential as a biofertilizer. NifA, the transcriptional activator of nitrogen fixation (nif) genes, and GlnB, one of PII signal transduction family protein, are key proteins in the regulation of nitrogen fixation in A. brasilense. It was previously reported that the regulation of NifA activity in A. brasilense depends on GlnB. We report here that GlnB was found to interact directly with the N-terminal domain of NifA in vivo under nitrogen-free conditions and the N-terminal mutant of NifA in which the Tyr residues at position 18 and 53 were replaced by Phe (NifA-N-Y18/53F) strengthened the interaction with GlnB. Moreover, we also found that the amino acid residues 66–88 and 165–176 in N-terminus of NifA are responsible for the interaction with GlnB.
Characterization of the flagellar biosynthesis regulatory geneflbD inAzospirillum brasilense
Juan Wang,Dalai Yan,Jilun Li
Chinese Science Bulletin , 2001, DOI: 10.1007/BF02901164
Abstract: A flagellar gene cluster fragment includingflbD ofAzospirillum brasilense was cloned and sequenced. TheflbD mutant strain was found to be nonmotile—losing both polar and lateral flagella (Fla Laf ). Motility and flagella were regained by complementation with plasmid-borne multicopyflbD, but altered with larger swarming circle and fewer lateral flagella on the semisolid plate. This result indicated that FlbD plays an important role in the regulation of both polar and lateral flagellar biosynthesis inA. brasilense.
Statistics and Analysis of the Results of the First-Class Think Tanks in the United States  [PDF]
Jiayin Liu, Jilun Li, Jing Qin
Open Access Library Journal (OALib Journal) , 2020, DOI: 10.4236/oalib.1106005
Abstract:
This article conducts quantitative analysis and research on the results of the first-class think tanks in the United States, and aims to provide reference for China’s developing first-rate think tanks and provide suggestions for future development routes. This article uses Elsevier’s Scopus database and SciVal analysis platform to quantitatively analyze the research results of 5 first-class think tanks in the United States in the past 10 years, using indicators such as h index, normalized impact factor, and high cited literature ratio to make a horizontal comparison of the development trends of the institutions, and further summarize and analyze on this basis. Through the analysis and research of the results of the five first-class think tanks in the United States, it provides a quantitative and in-depth important reference for China to build a world-class think tank.
Cloning and functional analysis of the sequences flanking mini-Tn5 in the magnetosome-deleted mutant NM21 of Magnetospirillum gryphiswaldense MSR-1
Feng Li,Ying Li,Wei Jiang,ZhenFang Wang,JiLun Li
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0235-y
Abstract: A magnetosome-deleted mutant NM21 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 lacZ2 transposon mutagenesis, and a 3073-bp fragment flanking mini-Tn5 lacZ2 in NM21 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved three putative ORFs; the mini-Tn5 lacZ2 was inserted into ORF1. Functional complementary test indicated that the 3073-bp fragment was required for biosynthesis of magnetosomes in M. gryphiswaldense MSR-1. The majority of proteins, which had homology with the protein encoded by ORF1, were the cation transporter. Transmembrane domain analysis showed that the protein encoded by ORF1 contained four transmembrane domains. It may be a transmembrane protein. The protein encoded by ORF1 contained two putative conserved domains: COG0053 and PRK09509. The MMT1 and FieF, containing conserved domains COG0053 and PRK09509 too, were Fe2+ transporter (cation diffusion facilitator superfamily). It was suggested that the protein encoded by ORF1 might take part in the magnetosomes biosynthesis as Fe2+ transporter.
Cloning and functional analysis of the sequences flanking mini-Tn5 in the magnetosomes deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1
Feng Li,Ying Li,Wei Jiang,Zhenfang Wang,Jilun Li
Science China Life Sciences , 2005, DOI: 10.1360/062005-26
Abstract: A magnetosome deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 transposon mutagenesis, and a 5045-bp fragment flanking mini-Tn5 in NM4 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved six putative open reading frames (ORFs); the mini-Tn5 was inserted into ORF4. Functional complementary test indicated that the 5045-bp fragment was required for biosynthesis of magnetosomes in M. gryphiswaldense MSR-1. The protein encoded by ORF4 had 25% of identity with the chemotaxis protein CheYIII of Caulobacter crescentus CB15, and the protein encoded by ORF4 contained a conserved signal receiver domain that can receive the signal from the sensor partner of the bacterial two-component systems. It was suggested that the protein encoded by ORF4 may take part in the signal transduction relating to biosynthesis of magnetosomes.
The secretion of lecithinase of Pseudomonas alcaligenes S2 was via type II secretion pathway
Jing Lü,Fan Li,Sanfeng Chen,Jilun Li
Chinese Science Bulletin , 2005, DOI: 10.1360/982005-548
Abstract: Strain S2 is a lecithin (or phosphatidylcholine)-solubilizing bacterium, which was isolated from the rice rhizosphere in rural areas of Beijing, China. On the basis of a polyphasic study involving phenotypic tests, physiological and biochemical tests, 16S rDNA sequence analysis, G+C content determination and DNA-DNA hybridizations analysis, strain S2 was identified as Pseudomonas alcaligenes. P. alcaligenes S2 was mutagenized with Tn5 and four mutants showing decreased or increased solubilizing ability of lecithin were isolated based on the halo size around colonies on the solid plate supplemented with egg yolk. To characterize the genes of P. alcaligenes S2 involved in solubilization of lecithin, the EcoR I fragments of the chromosomes from the four mutant strains carrying a single transposon were cloned, and the DNA sequences flanking the Tn5 were determined. The Tn5 insertion sites in the mutants M808, M1329 and M1400, showing decreased solubilizing ability of lecithin, were found to be located in the xcpS, xcpX and xcpW, respectively, whose products XcpS, XcpX and XcpW were the components of type II secretion pathway. Complementation of xcpS, xcpX and xcpW could restore the corresponding mutants M808, M1329 and M1400 to solubilize lecithin. The data suggested that mutation in one of these xcp genes would lead to the absence of mature lecithinase secretion into the extracellular medium. The data also indicated that the secretion of lecithin-hydrolyzing enzyme of P. alcaligeneswas via type II secretion pathway. In the mutant M20 showing increasing lecithin-hydrolyzing activity, the interrupted gene showed 86% identity with chpA of Pseudomonas aeruginosa PAO1, whose product plays an important role in controlling twitching motility of the bacterial cells.
Functional analysis of hydrogenases and their effects on cell growth and magnetosome synthesis in Magnetospirillum gryphiswaldense
Jia Ban,Wei Jiang,Ying Li,YaoPing Zhang,JiLun Li
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-009-0744-8
Abstract: This study addressed the effect of hydrogen metabolism on cell growth and magnetosome synthesis in Magnetospirillum gryphiswaldense strain MSR-1. Two deletion mutants were generated: L206, with single deletion of the hupL gene encoding H2-uptake [NiFe] hydrogenase; and B206, with double deletion of the hyaB gene encoding H2-producing [NiFe] hydrogenase and the hupL gene. The wild-type and mutant strains were compared in terms of hydrogen uptake capability, hydrogen yield, growth rate, and iron uptake, and observed by transmission electron microscopy. Results indicate that HupSL protein is a specific H2-uptake hydrogenase while HyaAB protein is a specific H2-producing hydrogenase. In comparison to wild-type and B206, L206 released a greater quantity of H2 under conditions that induce magnetosomes synthesis, and showed higher rates of growth and iron uptake. M. gryphiswaldense appears to regulate reducing power in vivo, via H2-uptake hydrogenase and H2-producing hydrogenase, to promote iron absorption and magnetosome synthesis.
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