Saliva-derived microcosm biofilm models for understanding oral microbial ecology

Oral biofilms are assemblages of microbes which adhere to intra-oral surfaces as structurally and functionally organized microbial communities. They are beneficial for marinating oral health when living in a state of homeostatic balance, or symbiosis, with the host. However, they are also responsible for the development of oral diseases once microbial composition of oral biofilms shifts to an imbalanced dysbiotic state. In this thesis, we aimed to develop biofilm models that can resemble the microbial shift from symbiotic to a pathogen-enriched dysbiotic state using in vitro saliva-derived microcosm biofilms. We first confirmed that oral biofilms were able to regrow shortly after treating by antimicrobial agents that are commonly used in clinic. The regrown biofilms showed reduced diversity and altered microbial composition, which may predispose the oral cavity to more aggressive and complicated infections. This observation highlights the importance of developing novel therapeutic strategies that can favorably modulate the microbial ecology of oral biofilms, rather than focusing solely on biofilm elimination. In view of this, we successfully established a series of biofilm models that can resemble the pathogen-enriched dysbiotic subgingival microbiota, by incorporating important periodontal microbes, such as Porphyromonas gingivalis, into in vitro saliva-derived microcosm biofilms. In addition, we demonstrated that such models can facilitate the evaluation of microbiome modulation strategies beneficial for oral microbial ecology.