The bar graphs represent the average (± standard deviation in error

bars) of normalized copy numbers × (μg S. mutans total RNA)-1. No significant differences were observed between S. mutans grown in mono-species and those grown in dual-species biofilms. Abbreviations: Sm, S. mutans; Ss, S. sanguinis; So, S. oralis; Lc, L. casei, with Sm-Ss, Sm-So and Sm-Lc indicating dual-species biofilm of the selected bacteria. S. mutans enhances biofilm formation by S. oralis and L. casei in dual-species model When grown on glass slides, S. mutans accumulated an average of 8.8 × 1010 CFU after 4 days (Figure 2). S. sanguinis TPCA-1 supplier also formed biofilms efficiently on glass surfaces, averaging 8.2 × 1010 CFU after 4 days. When these two learn more bacteria were grown in the dual-species model, the level of S. mutans decreased by more than 8-fold (P < 0.05), yielding an average of 1.0 × 1010 CFU, while S. sanguinis accumulated to 5.1 × 1010 CFU. S. oralis displayed a relatively poor capacity to form biofilms when grown alone, averaging 2.6 × 109 CFU after 4 days. When grown in dual-species with S. mutans, however, the number of S. oralis in the biofilms increased to an average of 1.4

× 1010 CFU (P < 0.01). On the other hand, biofilm formation by S. mutans was decreased when grown together with S. oralis, although the difference between mono-species and dual-species was not statistically significant. L. casei

alone formed biofilms poorly, accumulating only 2.9 × 107 CFU after 4 days. However, the capacity of L. casei to form biofilms was enhanced significantly VDA chemical inhibitor (P < 0.001) when co-cultivated with S. mutans, resulting in an increase of more than 60-fold to an average of 1.7 × 109 CFU after 4 days. Notably, when S. mutans was cultivated in dual-species biofilms with L. casei, the organisms accumulated in about 2-fold greater numbers than when S. mutans was grown PJ34 HCl alone, averaging 1.8 × 1011 CFU. Figure 2 Biofilm formation in mono- and dual-species model. Data presented here were generated from more than ten independent sets of experiments and were further analyzed using a non-parametric Kruskal-Wallis Test and student t-test. This graph shows the average (± standard deviation, in error bars) of CFU in biofilms formed by S. mutans and the other oral bacteria tested when grown in the mono- and dual-species models with S. mutans. A *, # and @ indicates significant difference at P < 0.05, 0.01 and 0.001, respectively, when compared to those grown in mono-species biofilms. All abbreviations are the same as in Figure 1. Various bacterial cell-cell interactions may exist when growing in dual-species biofilms, including competition for binding sites and nutrients available. In this study, the same amount of inoculum was used in mono- and dual-species biofilms.