中文摘要：

目的探讨变形链球菌临床株在浮游和生物膜两种不同生存状态下表面相关蛋白表达的变化情况，进一步了解龋病的发生和发展过程。方法采用Homer法提取593和18号临床株在浮游和生物膜状态下的表面相关蛋白，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，与浮游状态相比，生物膜状态两临床株的蛋白表达出现30％-31％的变化：18号菌株有238个蛋白出现≥1．3倍的表达变化，5个蛋白特异表达，5个蛋白失表达；593号菌株有279个蛋白出现≥1．3倍的表达变化，12个蛋白特异表达，2个蛋白失表达。其中，有3个蛋白的变化是两个菌株所共有的（1个蛋白共同特异表达，2个蛋白共同高表达），这些蛋白质的功能主要涉及生物合成过程。结论两临床株在生物膜状态均出现某些蛋白的特异和高表达，可能是菌株形成生物膜所共同必需的关键蛋白；两菌株间蛋白表达的差异可能是菌株各自特征的反映。

英文摘要：

Objective To investigate the changes in the surface-associated protein expression of planktonic cells and biofilm cells of clinical isolations of Streptococcus rnutans （Sin）. Methods The proteins were extracted by the method of Homer from the nonadhered planktonic and the adhered hiofilm cells and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis（SDS-PAGE） and two-dimensional gel elcctrophoresis followed by image analysis. Proteins were identified by matrix-assisted laser desorption time of flight mass spectrometry and computer-assisted protein sequence analysis. Results Image analysis revealed that 30%-31% of the protein spots in biofilm was modulated. A total of 238 proteins changed 1.3-fold or greater in biofilm cells compared to planktonic cells in Sm18, with 5 only expressed in biofilm cells and 5 not expressed in biofilm cells. A total of 279 proteins changed 1.3-fold or greater in biofilm cells compared to planktonic cells in Sm593, with 12 only expressed in biofilm cells and 2 not expressed in biofilm cells. Two clinical isolations in biofilm cells had three identical protein expressions whose functions were associated with biosynthetic processes. Conclusions The two clinical isolations in hiofilm status have high expression of some special proteins, which are presumed to be key proteins essential for formation of hiofilm. The difference of protein expression in hiofilm cells of the two clinical isolations may represent their distinct characters.