Characterization of OxyR homologue of Tannerella forsythia

Objectives: T. forsythia is an anaerobic periodontal pathogen which encounters constant oxidative stress in the oral cavity due to reactive oxidative species produced by other bacteria in the dental biofilm as well as by the host defenses such as neutrophils. The redox-sensitive transcriptional regulator OxyR regulates expression of downstream genes important in defense against oxidative responses in Gram-negative organisms. In this study, we sought to characterize the role of a putative OxyR homologue identified in the T. forsythia genome.

Methods: A mutant defective in the expression of an oxyR homologue in T. forsythia (gene id: TF0104) was constructed. The aerotolerance and survivability against hydrogen peroxide were determined. Moreover, transcriptional expression of oxyR-regulated genes involved in oxidative stress responses was determined by real-time PCR and compared with that of the parental strain. The ability of the oxyR mutant to form synergistic biofilms with Fusobacterium nucleatum was also determined, and compared with that of the parental strain.

Results: The survivability as well as tolerance to air exposure of the oxyR mutant was significantly decreased as compared to that of the parental strain. In addition, the T. forsythia oxyR mutant and F. nucleatum formed significantly less mixed biofilms as compared to the formation of biofilms between the T. forsythia parental strain and F. nucleatum.

Conclusion: An OxyR encoding gene has been identified in T. forsythiai in this study. The T. forsythia oxyR acts as a regulator of resistance to peroxide as well as oxygen (aerotolerance). In addition, OxyR is associated with biofilm formation in T. forsythia. This study was supported by NIDCR grant DE 014749.