中文摘要：

目的探讨变异链球菌临床株在pH7.0和pH5.0条件下的表面相关蛋白表达差异,进一步了解龋病发生和发展过程。方法采用Homer法提取593和18号（593号菌株分离于高发龋患者,18号菌株分离自无龋健康人）临床分离株在pH7.0和pH5.0条件下的表面相关蛋白,经十二烷基硫酸钠聚丙烯酰胺凝胶电泳和二维电泳确定蛋白表达的差异条带及位点,差异位点由基质辅助激光解析电离飞行时间质谱分析,并结合数据库进行检索和鉴定蛋白质。结果经过对电泳图谱的分析发现,两菌株在pH7.0条件下存在4个高表达位点和2个特异位点;在pH5.0条件下存在2个高表达位点和2个特异位点。593号菌株蛋白表达又发生了特殊的变化,即在pH5.0条件下,存在3个高表达位点和6个特异位点,其中双组分信号传导系统组氨酸激酶Lyts和3-磷酸甘油醛脱氢酶高表达,NADH氧化酶特异表达。结论两菌株在酸性变化下均出现了某些蛋白的高表达和特异表达,可能两菌株耐酸反应中存在相似之处;两菌株间蛋白表达差异可能是耐酸性存在差异的原因。

英文摘要：

Objective To investigate the changes in the surface-associated protein expression of streptococcus rnutans（Sm） isolated from clinical samples at pH7.0 and pH5.0. Methods The proteins were extracted from cells at pH7.0 andpH5.0 by Homer method. The proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis（SDS-PAGE） and two-dimensional gel electrophoresis followed by image analysis. Proteins were identified by matrix-assisted la-ser desorption ionization time of flight mass spectrometry and computer-assisted protein sequence analysis. Results Imageanalysis revealed that four high expression levels of protein loci and two specific protein loci were existed in two strains atpH7.0. Two high expression levels of protein loci and two specific protein loci were existed in two strains at pH5.0. Threehigh expression levels of protein loci and six specific protein loci were existed in Sm593 at pH5.0. Two-component systemhistidine kinases Lyts and glyceraldehyde- 3-phosphate dehydrogenase were highly modulated, and NADH oxidase weremodulated specifically. Conclusion The two clinical isolations in acid have high expression of some special proteins,which are presumed to be the resemblance of acid reaction.The difference of protein expression of two clinical isolations inacid may represent their distinct acid resistance.