Background: Streptococcus mutans (Sm) and Candida albicans (Ca) are found in biofilms of early childhood caries. Objective: To characterize in vitro dual- and single-species biofilms of Sm and Ca formed on saliva-coated hydroxyapatite discs in the presence of sucrose. Design: Evaluation of biofilms included biochemical [biomass, proteins, matrix’s water-soluble (WSP) and alkali-soluble (ASP) polysaccharides, microbiological, 3D structure, gene expression, and stress tolerance analyses. Results: Biomass and proteins were higher for dual-species and lower for Ca (p = 0.001). Comparison of Sm single- and dual-species biofilms revealed no significant difference in Sm numbers or quantity of WSP (p > 0.05). Dual-species biofilms contained a higher population of Ca (p < 0.001). The quantity of ASP was higher in dual-species biofilms (vs Ca single-species biofilms; p = 0.002). The 3D structure showed larger microcolonies and distinct distribution of Sm-derived exopolysaccharides in dual-species biofilms. Compared with dual-species biofilms, expression of gtfB (ASP) and nox1 (oxidative stress) was higher for single-species of Sm whilst expression of BGL2 (matrix), PHR1 (matrix, acid tolerance) and SOD1 (oxidative stress) was higher in single-species of Ca. There was no difference for acid tolerance genes (Sm atpD and Ca PHR2), which was confirmed by acid tolerance challenge. Dual-species biofilms were more tolerant to oxidative and antimicrobial stresses (p < 0.05). Conclusions: Dual-species biofilms present greater 3D complexity, thereby, making them more resistant to stress conditions.

背景：变形链球菌（Sm）和白色念珠菌（Cadida albicans，Ca）存在于儿童龋齿的生物膜中。目的：在蔗糖存在下，表征唾液包被的羟基磷灰石圆​​盘上形成的Sm和Ca的体外双物种和单物种生物膜。设计：生物膜的评估包括生物化学[生物量，蛋白质，基质的水溶性（WSP）和碱溶性（ASP）多糖，微生物学，3D结构，基因表达和胁迫耐受性分析。结果：双物种的生物质和蛋白质较高，而双物种的生物质和蛋白质较低。Ca（p = 0.001）。比较钐单和双物种生物膜揭示了无显著差异钐号码WSP（P> 0.05）的或数量。双物种生物膜包含较高的Ca种群（p <0.001）。双物种生物膜中的ASP含量较高（与Ca单物种生物膜相比； p = 0.002）。3D结构在双物种生物膜中显示出更大的微菌落和Sm衍生的胞外多糖的独特分布。与双物种生物膜相比，单种Sm的gtfB（ASP）和nox1（氧化应激）的表达更高而Ca的单一物种中BGL2（基质），PHR1（基质，耐酸性）和SOD1（氧化应激）的表达较高。耐酸基因（Sm atpD和Ca PHR2）没有差异，这已通过耐酸挑战得到了证实。双物种生物膜更能耐受氧化和抗微生物压力（p <0.05）。结论：双物种生物膜呈现出更高的3D复杂性，从而使它们更能抵抗压力条件。