The Role of Treponema denticola Motility in Synergistic Biofilm Formation With Porphyromonas gingivalis

Chronic periodontitis has a polymicrobial biofilm etiology and interactions between key oral bacterial species, such as and contribute to disease progression. and are co-localized in subgingival plaque and have been previously shown to exhibit strong synergy in growth, biofilm formation and virulence in an animal model of disease. The motility of , although not considered as a classic virulence factor, may be involved in synergistic biofilm development between and . We determined the role of motility in polymicrobial biofilm development using an optimized transformation protocol to produce two mutants targeting the motility machinery. These deletion mutants were non-motile and lacked the gene encoding the flagellar hook protein of the periplasmic flagella (Δ ) or a component of the stator motor that drives the flagella (Δ ). The specificity of these gene deletions was determined by whole genome sequencing. Quantitative proteomic analyses of mutant strains revealed that the specific inactivation of the motility-associated gene, , had effects beyond motility. There were 64 and 326 proteins that changed in abundance in the Δ and Δ mutants, respectively. In the Δ mutant, motility-associated proteins showed the most significant change in abundance confirming the phenotype change for the mutant was related to motility. However, the inactivation of as well as stopping motility also upregulated cellular stress responses in the mutant indicating pleiotropic effects of the mutation. wild-type and displayed synergistic biofilm development with a 2-fold higher biomass of the dual-species biofilms than the sum of the monospecies biofilms. Inactivation of and reduced this synergy. A 5-fold reduction in dual-species biofilm biomass was found with the motility-specific Δ mutant suggesting that periplasmic flagella are essential in synergistic biofilm formation with .