【摘要】 为分析单增李斯特菌重要毒力因子的遗传进化关系,并进一步探讨不同毒力菌株重要毒力因子的分子差异,分段扩增、克隆了3株不同毒力及不同血清型菌株的第1毒力岛(LIPI-1)全基因序列,对3株菌LIPI-1的6个毒力基因分别测序并进行了序列和系统进化分析。对其中毒力差异明显的2株菌,在分析其毒力表型的基础上,对其进行了分子特征和遗传变异分析。结果表明各毒力基因同源性各异,6个毒力基因反映出的进化关系不一致。弱毒株N21与强毒株Lmo0586相比,具有相似的溶血活性以及更强的溶脂活性。2株菌的调控序列prfA无明显差异;2株菌hly序列中的PEST基序有1个氨基酸发生了变化;2株菌的actA序列差异最显著,强毒株Lmo0586比弱毒株N21少105个核苷酸,造成35个氨基酸的缺失,该序列位于ActA蛋白的脯氨酸重复区内。更多还原

【Abstract】 The aim of this study was to analyze the genetic relationship of Listeria monocytogenes virulence genes,and to explore the molecular mechanism of its virulence attenuation.Six LIPI-1 gene clusters from three L.monocytogenes isolates with different virulence and serotypes were amplified by PCR and subsequently cloned.Based on the analysis of the virulence phenotype of two L.monocytogenes isolates with significant virulent difference,the molecular characterization and genetic variance were analyzed as follows.Sequence analysis and phylogeny among the six LIPI-1 sequences and others published clearly demonstrated that they had different sequence identities.Comparing the virulent isolate Lmo0586 with the attenuated isolate N21,the latter had similar hemolytic activity and greater fat soluble activity.It is supposed that the virulence attenuation of strain N21 may be due to one amino acid change in the PEST motif of the hly sequence.It was shown that actA sequence difference of the two isolates was significant,comparing Lmo0586 with the attenuated strain N21,and that 105 bp nucleotides in the proline rech region were missed,resulting in the deletion of 35 amino acids.更多还原