中文摘要：

目的：观察D-和L-游离氨基酸对变异链球菌生长及生物膜形成的影响。方法：将浓度为40 mmol/L的D-或L-半胱氨酸、酪氨酸、缬氨酸等20种游离氨基酸分别与变异链球菌UA159共同培养,分别于培养4、8、12、24 h各时间点对细菌进行活菌计数,以时间杀死（Tme-kill）法观察其对变异链球菌生长的影响;用结晶紫（Crystal violet,CV）染色法观察40 mmol/L游离氨基酸对变异链球菌生物膜形成的影响。结果：不同的氨基酸处理24 h后,D-半胱氨酸、D-精氨酸、L-赖氨酸可明显降低变异链球菌生存率（P〈0.05）;D-和L-天冬氨酸、谷氨酸可抑制变异链球菌的生长（P〈0.05）;D-苯丙氨酸、L-组氨酸、L-半胱氨酸处理组变异链球菌生存率呈现先下降后上升的趋势;D-和L-丝氨酸、酪氨酸、L-缬氨酸可延缓变异链球菌进入对数生长期;D-和L-谷氨酸、天冬氨酸、半胱氨酸、D-精氨酸、D-色氨酸可明显抑制变异链球菌生物膜的形成（P〈0.05）。结论：部分游离氨基酸对变异链球菌生长及生物膜的形成具有一定的抑制作用。

英文摘要：

AIM： To investigate the effects of free amino acids on the proliferation and biofilm formation of Streptococcus mutans（ S. mutans）. METHODS： S. mutans UA159 was cultured with 20 D- or L- free amino acids at 40 mmol /L recpectively. Time-kill assay was used to evaluate the proliferation of S. mutans,and the viable bacterial cells were counted by plate count at 4,8,12 and 24 h respectively after treatment. Crystal violet staining was used to observe the biofilm formation of S. mutans. RESULTS： D- Cys,D-Arg,L-Lys decreased S. mutans proliferation（ P〈0.05）; D-or L-enantiomers of Asp and Glu inhibited the proliferation of S. mutans（ P〈0. 05）; D-Phe,L-His,L-Cys decreased S. mutans proliferation at the early stage; D-or L-Ser,Tyr and L-Val delayed S. mutans proliferation at the exponential phase. D-or L-enantiomers of Cys,Asp,Glu,D-Arg,D-Trp inhibited the formation of S. mutans biofilm. CONCLUSION： Some free amino acids can inhibite the proliferation and biofilm formation of S. mutans.