AUTHOR=Ng Hong Min , Slakeski Nada , Butler Catherine A. , Veith Paul D. , Chen Yu-Yen , Liu Sze Wei , Hoffmann Brigitte , Dashper Stuart G. , Reynolds Eric C. 

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

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=9

YEAR=2019

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2019.00432

DOI=10.3389/fcimb.2019.00432

ISSN=2235-2988

ABSTRACT=<p>Chronic periodontitis has a polymicrobial biofilm etiology and interactions between key oral bacterial species, such as <italic>Porphyromonas gingivalis</italic> and <italic>Treponema denticola</italic> contribute to disease progression. <italic>P. gingivalis</italic> and <italic>T. denticola</italic> 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 <italic>T. denticola</italic>, although not considered as a classic virulence factor, may be involved in synergistic biofilm development between <italic>P. gingivalis</italic> and <italic>T. denticola</italic>. We determined the role of <italic>T. denticola</italic> motility in polymicrobial biofilm development using an optimized transformation protocol to produce two <italic>T. denticola</italic> 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<italic>flgE</italic>) or a component of the stator motor that drives the flagella (Δ<italic>motB</italic>). 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, <italic>motB</italic>, had effects beyond motility. There were 64 and 326 proteins that changed in abundance in the Δ<italic>flgE</italic> and Δ<italic>motB</italic> mutants, respectively. In the Δ<italic>flgE</italic> 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 <italic>motB</italic> as well as stopping motility also upregulated cellular stress responses in the mutant indicating pleiotropic effects of the mutation. <italic>T. denticola</italic> wild-type and <italic>P. gingivalis</italic> displayed synergistic biofilm development with a 2-fold higher biomass of the dual-species biofilms than the sum of the monospecies biofilms. Inactivation of <italic>T. denticola flgE</italic> and <italic>motB</italic> reduced this synergy. A 5-fold reduction in dual-species biofilm biomass was found with the motility-specific Δ<italic>flgE</italic> mutant suggesting that <italic>T. denticola</italic> periplasmic flagella are essential in synergistic biofilm formation with <italic>P. gingivalis</italic>.</p>