Tannerella forsythia is a major contributor to the aggressive form of periodontitis. These bacteria commonly exist as part of the sub-gingival plaque biofilm. However, there is currently limited information on the genetic and physiological mechanisms employed by T. forsythia during its adaptation to a biofilm lifestyle.
Objectives: The aim of this study was to investigate the physiological changes that Tannerella forsythia undergoes during early biofilm growth.
Methods: We used an iTRAQ shotgun proteomics approach to investigate differentially expressed proteins in biofilm compared to planktonic cells. In parallel we used a combination of RT-PCR, mutagenesis, recombinant protein expression and genetic complementation techniques to investigate differentially expressed proteins/genes and their role in biofilm physiology.
Results: 106 proteins were significantly up-or down-regulated (>1.4-fold). Several outer-membrane proteins, including putative transport systems and the Surface-layer proteins were markedly up-regulated. Enzyme levels in the terminal branch of the glutamate pathway, that might result in lower levels of the cytotoxic compound butyrate, were markedly down-regulated (3.8-5.3 fold). Furthermore, several oxidative stress-related proteins showed increased expression in biofilm cells and experiments revealed that such cells were 10-20-fold more resistant to Hydrogen Peroxide exposure than planktonic cells. There was also increased expression of proteins encoded by a putative sialic acid utilisation operon in biofilm cells. This was supported by the observation that sialic acid stimulated growth of T.forsythia biofilms and that the organism possesses a functional sialic acid uptake system.
Conclusion: This study has revealed several changes in the protein expression profile of biofilm cells which highlight a putative set of important adaptations made by T.forsythia that might help it achieve prolonged persistence and immune evasion in the oral cavity.