Dual-species biofilms of Streptococcus mutans and Candida albicans exhibit more biomass and are mutually beneficial compared with single-species biofilms

Carmélia Isabel Vitorino Lobo,Talita Baptista Rinaldi,Chiara Mikaella Somogyi Christiano,Luana De Sales Leite,Paula Aboud Barbugli,Marlise Inêz Klein

doi:10.1080/20002297.2019.1581520

Carmélia Isabel Vitorino Lobo, Talita Baptista Rinaldi + Show 4 more

Open Access

https://doi.org/10.1080/20002297.2019.1581520

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Abstract

ABSTRACTBackground: 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.

Highlights

Dental caries is a biofilm-diet-dependent disease that causes tooth demineralization by acids produced by microorganisms via the metabolism of dietary carbohydrates [1]
Children affected with ECC have a diet rich in carbohydrates, such as sucrose, which promotes the formation of microbial communities that are predominated by cariogenic/ aciduric microorganisms and consequent accumulation of virulent biofilms culminating with rapid destruction of dental tissue [2]
Dual-species biofilms with the four markers displayed less labeled of polysaccharides produced by C. albicans, with higher intensity of label in hyphae cells

Summary

Introduction

Dental caries is a biofilm-diet-dependent disease that causes tooth demineralization by acids produced by microorganisms via the metabolism of dietary carbohydrates [1]. Streptococcus mutans is still one of the main microorganisms associated with caries because it orchestrates the construction of the cariogenic biofilms by controlling the assembly of a matrix rich in insoluble exopolysaccharides, mainly α1,3-glucans [1,4]. It produces acids and survives in the acidic environment [5]. Candida albicans has been found in high numbers in cariogenic biofilms (mainly in ECC) [7,8,9,10] This fungus produces acids and survives in an acidic environment, synthetize proteinases that degrade collagen (among other exoenzymes [11,12]), which may contribute to the biofilm’s cariogenicity. Conclusions: Dual-species biofilms present greater 3D complexity, thereby, making them more resistant to stress conditions

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