The water-soluble mushroom extracts perturb the biofilm formation

Objectives: The water-soluble mushroom extracts were previously reported to have an inhibitory effect on sucrose-dependent biofilm formed by Streptococcus mutans. In this study, we investigated the glucosyltransferases (GTF) activity and expression of several genes in the biofilm form of S. mutans to elucidate the inhibitory mechanisms of biofilm formation by the extracts. Methods: S. mutans were grew in 96 well tissue culture plate containing THB with 1% sucrose with or without water-soluble extracts prepared from shiitake mushroom. Total RNAs were isolated from the biofilms and expression patterns of biofilm related genes were quantified by Real-time RT-PCR assay. The GTF activity in the biofilm form of S. mutans was also examined using recombinant GTFs. Results: The water-soluble shiitake extracts inhibited the GTF activities and expression of gtf genes. The extracts also inhibited the expression of cell surface protein antigen I/II (PAc, SpaP) and glucan binding protein genes. Several gene expressions involved in biofilm related two-component systems were also inhibited. Conclusion: The water-soluble extracts of shiitake mushroom inhibit the biofilm formation by avoiding glucan synthesis. In addition, the extracts seem to perturb the expression of regulatory genes associated with biofilm formation. Water-soluble extracts may contain several factors to inhibit the biofilm formation. [This study is supported by JSPS grant (21792165).]