中文摘要：

目的：观察酸性环境对变形链球菌初始黏附相关基因spaP表达的影响。方法：变形链球菌分别在初始pH为5．5和7．0的条件下培养，提取总RNA，逆转录成cDNA，利用TaqMan实时荧光定量PCR技术检测不同环境条件下变形链球菌初始黏附相关基因spaP的表达。结果：pH5．5的酸性环境中变形链球菌spaP基因表达显著下调（P〈0．05）；黏附较强的变形链球菌菌株无论在中性还是酸性的环境中，其spaP基因的表达总体上高于黏附较弱的菌株。结论：酸性环境抑制变形链球菌spaP基因表达可能是酸性环境中变形链球菌初始黏附下降的机制之一；变形链球菌对牙面的黏附力可能与其spaP表达的量有关。

英文摘要：

Objective：To detect the influence of acidic environment on expression of spaP, the main initial adherence associated gene of S. mutans. Methods： Total RNA was extracted from S. mutans after being cultured in the medium at initial pH of 5.5 or 7.0 and then reversely transcripted to cDNA. By utilizing TaqMan RT-RCR technique, spaP expression was checked. Results： In acidic environment, spaP expression of S. mutans was decreased significantly. No matter the initial pH of medium was acidic or neutral, spaP expression of more-adherent S. mutans strains was generally higher than that of less-adherent strains. Conclusion ： The inhibition of spaP expression may be one of the mechanisms underlying the decreased initial adherence of S. mutans in acidic environment; There might be some correlation between the expression of spaP gene and S. mutans initial adherence.