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The OxyR homologue in Tannerella forsythia regulates expression of oxidative stress responses and biofilm formation

¹ University at Buffalo;
² Department of Microbiology, Tokyo Dental College

ABSTRACT

Tannerella forsythia is an anaerobic periodontal pathogen which encounters constant oxidative stress in the human oral cavity due to exposure to air and reactive oxidative species from coexisting dental plaque bacteria as well as leukocytes. In this study, we sought to characterize a T. forsythia open reading frame with close similarity to bacterial oxidative-stress response sensor protein OxyR. To analyze the role of this OxyR homologue, a gene deletion mutant was constructed and characterized. Aerotolerance, survivability after hydrogen peroxide challenge and transcription levels of known bacterial anti-oxidant genes were then determined. Since association between oxidative stress and biofilm formation has been observed in bacterial systems, we also investigated the role of the OxyR protein in biofilm development by T. forsythia. Our results showed that aerotolerance, sensitivity to peroxide challenge and the expression of oxidative stress response genes was significantly reduced in the mutant as compared to that in the wild-type strain. Moreover, the results of biofilm analyses showed that as compared to the wild-type strain, the oxyR mutant showed significantly less autoaggregation and reduced ability to form mixed biofilms with Fusobacterium nucleatum. In conclusion, a gene annotated in the T. forsythia genome as an oxyR homologue was characterized. Our studies showed that the oxyR homologue in T. forsythia constitutively activates anti-oxidant genes involved in resistance to peroxides as well as oxygen stress (aerotolerance). In addition, the oxyR deletion attenuates biofilm formation in T. forsythia.

³ E-mail: sharmaa{at}buffalo.edu

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