IADR Abstract Archives
Streptococcus sanguinis Inhibits Candida albicans Accumulation in Mixed-Species Biofilms
Objectives: Streptococcus sanguinis (Ss) is a commensal inhabitant in the oral cavity and is associated with healthy teeth free of dental caries. In contrast, Streptococcus mutans is the main cariogenic bacterium and is frequently detected with the opportunistic fungus Candida albicans (Ca), particularly in early-childhood caries. The effect of S. sanguinis on C. albicans has not been characterized. Here, we investigated the development and interplay of Ss-Ca mixed species biofilms using microbiological and proteomics techniques.
Methods:
Mono-species and Ss-Ca mixed-species biofilms were quantified by XTT assay and CFU counting. Biofilms were visualized using confocal microscopy and biovolume quantification via Imaris software. Fungal growth was evaluated using optical density measurements. Ss-Ca protein expression in mixed-species biofilm was evaluated using quantitative proteomics (iTRAQ) followed by Gene-ontology pathway analysis (Cytoscape-v2.8.3).
Results: There was no significant difference in the number of S. sanguinis cells in mixed-species biofilms. However, the presence of S. sanguinis significantly inhibited the biofilm formation of C. albicans as determined by CFU counting (P<0.05). Confocal microscopy showed a drastic reduction in C. albicans yeast cells. S. sanguinis protein profile was not affected by the presence of C. albicans. Conversely, C. albicans proteomic profile in mixed-species biofilm was significantly altered. Proteins associated with oxidative stress response were upregulated indicating that C. albicans is under oxidative stress. Proteins related to pyruvate conversion into ethanol (pyruvate decarboxylase, aldehyde dehydrogenase) and lactic acid (lactate dehydrogenase) was downregulated (P<0.05). Proteins in the glyoxalate pathway and gluconeogenesis was significantly upregulated indicating the lack of carbon sources available for C. albicans indicating competition with S. sanguinis for nutrients.
Conclusions: Our data reveal that S. sangunis inhibits the accumulation of C. albicans in mixed-species biofilms through imparting oxidative stress and affecting the carbohydrate metabolism of the fungus. This may explain a protective effect of S. sanguinis against dental caries.
Methods:
Mono-species and Ss-Ca mixed-species biofilms were quantified by XTT assay and CFU counting. Biofilms were visualized using confocal microscopy and biovolume quantification via Imaris software. Fungal growth was evaluated using optical density measurements. Ss-Ca protein expression in mixed-species biofilm was evaluated using quantitative proteomics (iTRAQ) followed by Gene-ontology pathway analysis (Cytoscape-v2.8.3).
Results: There was no significant difference in the number of S. sanguinis cells in mixed-species biofilms. However, the presence of S. sanguinis significantly inhibited the biofilm formation of C. albicans as determined by CFU counting (P<0.05). Confocal microscopy showed a drastic reduction in C. albicans yeast cells. S. sanguinis protein profile was not affected by the presence of C. albicans. Conversely, C. albicans proteomic profile in mixed-species biofilm was significantly altered. Proteins associated with oxidative stress response were upregulated indicating that C. albicans is under oxidative stress. Proteins related to pyruvate conversion into ethanol (pyruvate decarboxylase, aldehyde dehydrogenase) and lactic acid (lactate dehydrogenase) was downregulated (P<0.05). Proteins in the glyoxalate pathway and gluconeogenesis was significantly upregulated indicating the lack of carbon sources available for C. albicans indicating competition with S. sanguinis for nutrients.
Conclusions: Our data reveal that S. sangunis inhibits the accumulation of C. albicans in mixed-species biofilms through imparting oxidative stress and affecting the carbohydrate metabolism of the fungus. This may explain a protective effect of S. sanguinis against dental caries.