Microbial Coaggregation in the Oral Cavity: Molecular Interactions and Current Insights

Periodontitis is a chronic inflammatory disease of the periodontal tissues primarily caused by dysbiotic bacterial communities. Accumulating evidence suggests that periodontal pathogens not only drive the initiation and progression of periodontitis but also significantly contribute to systemic disorders, including diabetes mellitus, cardiovascular disease, cancer, and adverse pregnancy outcomes, such as preterm birth. The key periodontal pathogens implicated in disease pathogenesis include Porphyromonas gingivalis, Prevotella intermedia, Treponema denticola, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, and Fusobacterium nucleatum. Among the diverse factors governing bacterial colonization and biofilm formation, interspecies interactions, particularly coaggregation, play a critical role in dental plaque maturation and the establishment of pathogenic microbial communities. Coaggregation facilitates the spatial organization of bacteria within biofilms, enhances bacterial survival, and modulates virulence factor expression. This review summarizes current knowledge regarding bacterial interactions involving major periodontal pathogens, with particular emphasis on coaggregation mechanisms, and discusses the implications of this coaggregation for periodontitis pathogenesis and associated systemic diseases.