Study Of Sulfurmetabolism Function For LuxS Gene Of The Streptococcus Mutans

Objective:In order to study the difference of the biofilm at different periods for the Streptococcus mutans standard strain and luxS mutant strain, the biofilm models for the two kinds of strains were built. The sulfur metabolism role of luxS gene for Streptococcus mutans were investigated by comparing the growth and biofilm of two kilnds of strains.Methods:The biofilm models of both Streptococcus mutans standards strain and luxS mutant strain were built on the slides carriers, the luxS mutant strain was successfully built in our previous experiments. The differences of biofilms between the two strains at different periods were observed using converted fluorescence microscope after dyeing by means of acridine orange(AO). The cultivation of the two strains was carried out by nutritional complementation experiments. Confocal Laser scanning microscope (CLSM) was used to observe and determinate the thickness of biofilm and mean fluorecence intensity.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. The biofilm specimens of two kinds of strains in diffrent periods by processing and preserving made no changes after three months. The significant increases in the thickness of mutant strain biofilm and its growth were observed after the addition of cysteine, but did not reach the standards strain levels. When methionine and S-adenosylhomocysteine of certain concentrations were respectively added, the biofilm thickness and the growth of mutant strain were raised but did not reach the level of the standards strain. When adding the supernatant fluid of standard strains, the biofilm thickness and the growth levels of mutant strain were much higher than those of the standards strain. The biofilm thickness and growth of both kinds of strains decreased after the addition of S-adenosylmethionine. The thickness of biofilm and mean fluorecence intensity are irrelevant.Conclusions: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. The luxS gene plays not only a role in quorum sensing but also a role in sulfurmetabolism.