Abstract: [Abstract] Objective To study the difference of biofilm formation at different times between Streptococcus mutans Ingbritt C international standards strain and LuxS mutant strain by dynamic viewing of converted fluorescence microscope. Methods The biofilm models of both Streptococcus mutans standards strain and LuxS mutant strain were built on the slides carriers in 6,18,24,48h respectively. The biofilms of the two strains and the relative mobility between the bacteria were observed using converted fluorescence microscope after dyeing by means of acridine orange(AO). Results The biofilms in the microtiter plates could be observed dynamically by converted fluorescence microscope, There are variety in morphology of the two stains; the biofilms began to form with the bacteria gathering densely at 6h.Those of 18h and 24h were the best formation, they can adhere to slides carrier very firmly and can not be washed out; at the time of 48h,the adhesive capacity of the standards strain was lower than LuxS mutant strain, the whole biofilm of the standards strain was prone to slide. Conclusion The biofilms of Streptococcus mutans standard s strain and LuxS mutant strain were three-dimensioned and variety in morphology, in addition, at different point-in-times, they displayed a marked difference in the form of biofilm , reciprocity of bacteria and adhesive power.

Key words: Streptococcus mutans, LuxS mutant strain, Acridine Orange(AO), Converted Fluorescence Microscope