ABSTRACT
Objective To construct sigF deletion mutant of Bacillus anthracis and the complementary strain of sigF deletion mutant in order to analyze the effect of losing sigF on formation of spores.Methods The spectinomycinadenyltransferase gene(spc) was inserted to replace sigF of B.anthracis by homologous recombination.A plasmid which contained sigF and sigF promotor was constructed and then transferred to the mutant to get a complementary strain of sigF deletion mutant.The characters of the mutant were analyzed by measuring growth curves, the ability of carbohydrate metabolism was compared, and spore formation was observed under a microscope.Results The sigF deletion strain A16D2△sigF was constructed from A16D2,which had a similar growth rate to the wild type A16D2 in logarithmic phase, but was not significantly different from the initial strain in the ability to use carbohydrates,although unable to form spores.The strain was found to maintain the state of asymmetric division by microfluidics experiment.Conclusion It is showed by this study that sigF is the essential gene of B.anthracis for spore formation, but not essential for vegetative growth.
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Objective To achieve arabinose-controlled expression of HtrA strain and detect the expression of HtrA protein.Methods Arabinose promoter with htrA100 was amplified from pACD-htrA vector by PCR and cloned into pGP704 vector.Then, Shigella flexneri 2a strain 301 was transferred with the recombinant plasmid pGD-htrA and an AraC-expression vector .The expressions of HtrA in whole-cell and periplasmic space were detected by Western blotting .Results The suicide plasmid-mediated homologous recombinant vector and the inducible HtrA expression strain were successfully constructed.Without arabinose,HtrA protein was hardly detected ,but in the presense of arabinose , HtrA protein could be detected in whole-cell lysate and in periplasmic space lysate by Western blot .Conclusion Homologous recombination using suicide plasmid can significantly knock down the expression of HtrA protein .After being induced with arabinose , HtrA protein can be expressed normally .
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Objective To explore the potential pathogenesis of Yersinia pestis and provide new clues for vaccine development through comparative proteomic analysis of wild-type and pCD1 cured strain of Yersinia pestis 201.Methods Differentially expressed proteins at 26℃ and 37℃ were separated and identified using two-dimensional electrophoresis coupled with mass spectrometry .Results A total of 24 differently expressed proteins were successfully identified from the samples of bacteria grown at 26℃ and 25 proteins at 37℃.Among these, 7 proteins were encoded by pCD 1 plasmid. Conclusion Through comparative proteomic research, we have found that the abundance of several proteins can be dramatically changed when the large plasmid pCD 1 is missing,suggesting that the plasmid can regulate the expression of many genes located in the chromosome .
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Objective To compare the separation effects of protein samples extracted by two different methods with two -dimensional gel electrophoresis (2-DE) .Methods Ultrasonic disruption and glass-beads grounding were used to prepare protein samples of Gram-negative bacteria , Gram-positive bacteria and animal tissues .The actual results of the two sample preparation methods were compared by 2-DE.Results The 2-DE maps of samples extracted by the two methods were obtained.Conclusion The 2-DE maps of glass-beads grounding samples are better than those of ultrasonic disruption thanks to their lower backgrounds , which are beneficial for further image analyses .
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Objective To explore the function of gene phoN1 in Shigella flexneri.Method Using the λ-Red recombi-nant system, phoN1was knocked out from S.flexneri 2a strain 301.Comparative proteomics was performed to analyze the differences between mutant and wild-type strains in protein expression profiles .Sereny tests and competitive infection assays were carried out to compare the virulence of mutant and wild-type strains .Results The deletion mutant of phoN1 was suc-cessfully constructed .No significant difference between the two strains was found in the comparative proteomics analyses . The function of gene phoN1 might be unrelated to the invasion ability of S.flexneri according to the results of Sereny tests and competitive infection assays .Conclusion Gene phoN1 might be of no use for the in vitro survival and host cell invasion of S.flexneri.
ABSTRACT
In order to remove invasive plasmids from Shigella flexneri 2a 2457T and Shigella sonnei S7 based on the principle of plasmid incompatibility Ori and inc genes were amplified by PCR from S. flexneri 2a invasive plasmids, and then they were cloned into plasmid pMD18 T, resulting recombinant plasmids pMDori and pMDinc After S flexneri 2a 2457T and S sonnei S7 were transformed with pMDori or pMDinc respectively Invasive plasmids were removed from S flexneri 2a 2457T and S sonnei S7