Effects of Different Substrates/Growth Media on Salivary Biofilm Microbial Community

Objectives: Dental caries poses a major health problem worldwide. More researchers have accepted the caries ecological hypothesis. Salivary biofilm, a salivary microbial community, is widely used as a dental plaque microcosm model in vitro. The objectives of this study were to investigate the effects of different substrates (glass versus hydroxyapatite HA) and growth media (Shi medium versus McBain medium) on microbial community of salivary biofilms.
Methods: Salivary biofilms were cultured in Shi medium/modified artificial saliva medium with cysteine (McBain medium) on glass and HA disks for 72 h anaerobically. 16S rRNA gene sequencing was used to analyze the microbial community of salivary biofilms. LEfSe analysis was used to display the community structure. Metagenomes of salivary biofilms were predicted from the clusters of orthologous groups (COGs).
Results: No significant difference was found in ACE, Chao, Shannon, Simpson indices and gene predictions among salivary biofilms on HA versus glass disks. LEfSe analysis showed that the relative abundances of Fusobacterium, Capnocytophaga, Lachnoanaerobaculum, Bergeyella and Parvimonas in biofilms on HA were significantly different from those on glass, which were in a low relative abundance (<0.5%). Compared with those cultured in McBain medium, the biofilms cultured in Shi medium were significantly higher (p<0.05) in alpha diversity. In community structure and predicted genes, they were different from each other (p<0.05). The relative abundance of Veillonella, Fusobacterium, Lachnoanaerobaculum, Porphyromonas, Alloprevotella and Bergeyella was significantly higher (p<0.05) in Shi medium biofilms, while that of Moraxella was higher (p < 0.05) in McBain medium biofilms.
Conclusions: The different substrates did not, but the different media did, have significant effects on the microbial community of salivary biofilm. Therefore, in caries studies, both HA and glass can be used as biofilm substrates. However, Shi medium or McBain medium must be selected based on the purpose and nature of the research.