Evaluation of microbial interactions and the role of Streptococcus oralis and Actinomyces oris adhesins in the formation and structure of mixed biofilms with Candida albicans

Author(s)

Indira Moraes Gomes Cavalcanti

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2016-03-29

Examining board members

Altair Antoninha Del Bel Cury; Carlos Estrela; Marlise Inêz Klein; Livia Maria Andaló Tenuta; Antônio Pedro Ricomini Filho

• Advisor: Altair Antoninha Del Bel Cury

Abstract

The evaluation of microbial interactions is extremely important for the comprehension of communities¿ development and their control. As biofilm form, bacteria are adhered to salivary-pellicle covered-surfaces and still interacting with other species for coadhesion and coaggregation. These interactions occur due to adhesins molecules present onto microorganisms surfaces. Two important adhesins are the Receptor of Polysaccharide (RPS) in S. oralis (So) and fimbriae onto Actinomyces oris (Ao) surface, both bacteria are first colonizers of oral surfaces. These adhesins have essential role in bacterial adhesion onto the pellicle, in the interaction with other microorganisms and on biofilm formation. Their relationship and the molecular base of interactions with the fungus C. albicans are still under investigation. The aims of this study were to evaluate the interactions between S. oralis (So), A. oris (Ao) with C. albicans (Ca) and the role of RPS and Fimbriae I/II planktonically and as biofilms. Combinations of dual and triadic species in wild types and mutants strains lacking RPS and Fimbriae types I and II were designed for that: I (Ao + Ca), II (So + Ca), III (So + Ao + Ca), IV (Ao ?Fim + Ca), V (So ?RPS + Ca), VI (Ao ?Fim + So + Ca) and VII (Ao ?Fim + So ?RPS + Ca). The mono-species biofilms were developed as well. The microorganisms grown planktonically for 3 hours in YPTG medium (YNB, peptone, triptone in phosphate buffer supplemented with glucose) and the interactions evaluated by fluorescence microscopy. The biofilms were developed onto resin discs and glass cover slips covered with salivary pellicle (2 hours) in the same medium until 24 hours. The viability was determined by biomass in 7 hours biofilms and Colony-forming units (CFU/mL) in 1.5 and 24 hours biofilms. The temporal development and microbial distribution were evaluated by confocal, optical and fluorescence microscopies. So and Ao interacted as wild types and particular biofilm formation was observed in the presence of one or two mutant strains. All bacteria interacted planktonically with Ca in all combinations and do not compete for binding sites onto fungal surface. The presence of Ca in biofilms influenced the bacterial community improvement, Ao mutant strain to biofilm formation and bacteria stimulated hyphal growth. There is a new distribution and cell prevalence in three-species biofilms containing mutant bacteria. Based on these results, it can be concluded that first colonizers bacteria So and Ao interact with Ca planktonically or within biofilms, although the interspecies interactions are RPS and fimbriae independent (AU)

• FAPESP's process: 13/15884-1 - Evaluation of microbial interactions and the role of surface adhesins of initial colonizers Streptococcus oralis and Actinomyces naeslundii in the formation and structure Candida albicans biofilms.
• Grantee: Indira Moraes Gomes Cavalcanti
• Support Opportunities: Scholarships in Brazil - Doctorate