ObjectiveThis study aims to investigate the structural differences, dominant bacterial genera, and potential functions of microbial communities in different oral ecological niches (dorsal tongue, tooth surface, and buccal mucosa) of preschool children to clarify the influence of local microenvironments on microbial colonization and provide a theoretical basis for the microbiota-targeted regulation of pediatric oral diseases.MethodsA total of 105 plaque samples were collected from the dorsal tongue, tooth surface, and buccal mucosa of 35 healthy preschool children (aged 4-6 years). High-throughput sequencing of the 16S rRNA gene was performed to analyze the microbial community structure and alpha/beta diversity. Principal coordinate analysis, UPGMA clustering, and LEfSe analysis were used to identify niche-specific dominant genera. PICRUSt2 was applied to predict the potential metabolic functional profiles across niches.ResultsSpatial hete-rogeneity in microbial composition and structure was observed across the three oral niches. Species richness was significantly higher on the tooth surface and buccal mucosa than on the dorsal tongue. The dominant phyla included Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes, Fusobacteria, and Patescibacteria. At the genus level, Actinomyces and Corynebacterium were enriched on the tooth surface, Veillonella was enriched on the dorsal tongue, and Streptococcus was predominant on the buccal mucosa. Beta diversity and clustering analyses confirmed distinct microbial community structures among the niches. LEfSe analysis identified several niche-specific genera. PICRUSt2 functional prediction revealed significant differences in amino acid metabolism, carbohydrate metabolism, cell motility, translation, signal transduction, immune system, infectious disea-ses, and membrane transport (P<0 .05).ConclusionThe dorsal tongue, tooth surface, and buccal mucosa in preschool children harbor distinct microbial communities with different taxonomic composition, diversity, and functional potential. The findings suggest that local microenvironmental factors shape oral microbiota and may contribute to the early onset of oral diseases. This study provides foundational data and theoretical insights for early microbiome-based risk assessment and personalized oral health interventions in children.
