Objective: To knock out the entire Luxs gene of Streptococcus mutans(S.mutans) UA159 strain via homologous recombination and construct a Luxs-deleted mutant strain of S. mutans. To study the difference between the aci...Objective: To knock out the entire Luxs gene of Streptococcus mutans(S.mutans) UA159 strain via homologous recombination and construct a Luxs-deleted mutant strain of S. mutans. To study the difference between the acid resistance of S. mutans Ingbritt C international standard strain and the acid resistance of LuxS mutant strain. Methods: Two DNA fragments locating in the upper and downstream of Luxs gene were amplified and a erythromycin resistance gene of PJT10 between them were engineered into PUC19 plasmid for constructing the recombination plasmid pUCluxKO. Electrotransformation of S.mutans cells with pUCluxKO-mutant resulted in isolation of erythromycin resistant S. mutans transformants, which was identified by polymerase chain reaction, V.harveyi BB170 luminescence bioassay and sequencing analysis. Solutions of S. mutans standard strain and LuxS mutant strain with same density were made and cultured at pH 3.5 to 7.0 BHI liquid for the same period.Terminal growth situation was compared.Firstly acidized in pH 5.5 BHI liquid,the two strains were cultured at pH 3.0 BHI liquid. The acid tolerance responses of the two strains were compared.Results:Restriction endonuclease analyses showed that pUCluxKO-mutant vector had been successfully recombined. The Luxs-deleted status of S.mutans mutants was confirmed by PCR with primers which were specific for the genes of Luxs and Erythromycin resistance. S.mutans mutant can not induce bioluminescence, indiating the mutant had been successfully recombined. After twenty generations of culture, the constructed Chinese S.mutans mutants were confirmed to be stable. Significant difference of aciduricity was observed between S.mutans standard strain and LuxS mutant strain.The acid resistance of standard strain was stronger than that of LuxS mutant strain.The two strains both displayed the capability of acid tolerance responses. Conclusion:The S.mutans gene allelic exchange plasmid is constructed correctively and a Luxs-negative mutants of S.mutans is constructed, which can help to further study the role of Luxs in the pathogenesis of S.mutans. LuxS mutant strain is more sensitive to acid inactivation,but the capability of acid tolerance responses exist still.展开更多
目的探讨C基因截短突变体抗乙型肝炎病毒(HBV)的作用机制。 方法 构建C基因截短的真核表达载体pcDNA3—△ C及野生型C基因真核表达载体pcDNA3—C,瞬时转染HepG2细胞,用SDS—PAGE western blot检测pcDNA3—△C、pcDNA3-C的蛋白表达。pcD...目的探讨C基因截短突变体抗乙型肝炎病毒(HBV)的作用机制。 方法 构建C基因截短的真核表达载体pcDNA3—△ C及野生型C基因真核表达载体pcDNA3—C,瞬时转染HepG2细胞,用SDS—PAGE western blot检测pcDNA3—△C、pcDNA3-C的蛋白表达。pcDNA3—△ C与adwR9共转染HepG2细胞,以pcDNA3与adwR9为对照,用荧光定量PCR检测培养上清液及细胞内病毒量,用Native western blot 分析C基因截短蛋白干扰核心颗粒形成。 结果 重组载体pcDNA3—△ C、pcDNA3—C均可表达,pcDNA3-△C与adwR9共转染组上清液和细胞内病毒量较对照组降低,pcDNA3—△ C和pcDNA3—C共转染组Native western blot条带与pcDNA3和pcDNA3—C共转染组条带相比较明显淡。 结论 C基因截短突变体可干扰核心颗粒的形成,导致HBV复制下降。展开更多
文摘Objective: To knock out the entire Luxs gene of Streptococcus mutans(S.mutans) UA159 strain via homologous recombination and construct a Luxs-deleted mutant strain of S. mutans. To study the difference between the acid resistance of S. mutans Ingbritt C international standard strain and the acid resistance of LuxS mutant strain. Methods: Two DNA fragments locating in the upper and downstream of Luxs gene were amplified and a erythromycin resistance gene of PJT10 between them were engineered into PUC19 plasmid for constructing the recombination plasmid pUCluxKO. Electrotransformation of S.mutans cells with pUCluxKO-mutant resulted in isolation of erythromycin resistant S. mutans transformants, which was identified by polymerase chain reaction, V.harveyi BB170 luminescence bioassay and sequencing analysis. Solutions of S. mutans standard strain and LuxS mutant strain with same density were made and cultured at pH 3.5 to 7.0 BHI liquid for the same period.Terminal growth situation was compared.Firstly acidized in pH 5.5 BHI liquid,the two strains were cultured at pH 3.0 BHI liquid. The acid tolerance responses of the two strains were compared.Results:Restriction endonuclease analyses showed that pUCluxKO-mutant vector had been successfully recombined. The Luxs-deleted status of S.mutans mutants was confirmed by PCR with primers which were specific for the genes of Luxs and Erythromycin resistance. S.mutans mutant can not induce bioluminescence, indiating the mutant had been successfully recombined. After twenty generations of culture, the constructed Chinese S.mutans mutants were confirmed to be stable. Significant difference of aciduricity was observed between S.mutans standard strain and LuxS mutant strain.The acid resistance of standard strain was stronger than that of LuxS mutant strain.The two strains both displayed the capability of acid tolerance responses. Conclusion:The S.mutans gene allelic exchange plasmid is constructed correctively and a Luxs-negative mutants of S.mutans is constructed, which can help to further study the role of Luxs in the pathogenesis of S.mutans. LuxS mutant strain is more sensitive to acid inactivation,but the capability of acid tolerance responses exist still.
文摘目的探讨C基因截短突变体抗乙型肝炎病毒(HBV)的作用机制。 方法 构建C基因截短的真核表达载体pcDNA3—△ C及野生型C基因真核表达载体pcDNA3—C,瞬时转染HepG2细胞,用SDS—PAGE western blot检测pcDNA3—△C、pcDNA3-C的蛋白表达。pcDNA3—△ C与adwR9共转染HepG2细胞,以pcDNA3与adwR9为对照,用荧光定量PCR检测培养上清液及细胞内病毒量,用Native western blot 分析C基因截短蛋白干扰核心颗粒形成。 结果 重组载体pcDNA3—△ C、pcDNA3—C均可表达,pcDNA3-△C与adwR9共转染组上清液和细胞内病毒量较对照组降低,pcDNA3—△ C和pcDNA3—C共转染组Native western blot条带与pcDNA3和pcDNA3—C共转染组条带相比较明显淡。 结论 C基因截短突变体可干扰核心颗粒的形成,导致HBV复制下降。