Objective To construct luxS mutant aften luxS gene of Streptococcus mutans（S.mutans） was knocked out, and examine their ability of biofilm formation. Methods A recombinant plasmid containing the flanking fragment of luxS of S.mutans was transformed into S.mutans UA159, and selected by brain heart infusion（BHI） agar medium with kanamicin. The luxS mutant further confirmed via polymerase chain reaction（PCR） and the autoinducer-2（AI-2） bioluminescence assay of Vibrio harveyi（V.harveyi）, and ability of luxS mutant and S.mutans UA159 biofilm formation was examined in different phases, in BHI medium with 1% sucrose and 1% glycose by scanning electron microscopy （SEM）. Results LuxS-deficient S.mutans strains were successfully constructed. Compared with S.mutans UA159, the luxS mutant maintained in BHI medium containing 1% sucrose displayed an apparent defect in biofilm formation, while they showed no significant deviation in BHI medium containing 1% glycose. Conclusion luxS gene in S.mutans can play a role in dental plaque biofilm formation, and the luxS gene is possible to regulate sucrose -dependent biofilm formation.
