# Ecological and Functional Landscape of the Oral Microbiome: A Multi-Site Analysis of Saliva, Dental Plaque and Tongue Coating

## TL;DR

This study explores how different parts of the mouth, like saliva, plaque, and tongue coating, host unique microbial communities shaped by their environment and host factors.

## Contribution

The study reveals that oral microbial composition and function vary independently across niches, emphasizing the need for multi-site sampling.

## Key findings

- Saliva and tongue coating showed taxonomic similarity but were influenced by different host factors.
- Tongue coating showed the most functional divergence despite its taxonomic similarity to saliva.
- Plaque maintained a distinct biofilm-like structure with limited systemic influence.

## Abstract

The oral cavity contains several microbial niches, including saliva, dental plaque and tongue coating, each shaped by distinct local environments and host factors. This study compared the ecological and functional characteristics of the microbiomes of these three oral sites within the same individuals and examined host conditions associated with their variation. Saliva, supragingival plaque and tongue coating samples were collected simultaneously from 31 adults without clinical oral lesions. The bacterial 16S rRNA gene (V3–V4 region) was sequenced using the Illumina MiSeq platform, and analyses included α and β diversity, Mantel correlations, differential abundance tests, network analysis and functional prediction. The three sites displayed a clear ecological gradient. Saliva and tongue coating were taxonomically similar but were influenced by different host factors, whereas plaque maintained a distinct, biofilm-like structure with limited systemic influence. Functional divergence was most pronounced on the tongue coating despite its taxonomic similarity to saliva, whereas functional differences between saliva and plaque were modest despite larger taxonomic separation. These findings indicate that microbial composition and function vary independently across oral niches and support the need for multi-site sampling to more accurately characterize oral microbial ecology.