The transcriptional regulator oxtR and its involvement in oxygen stress response in T. denticola

Treponema denticola has been strongly implicated in the pathogenesis of chronic periodontitis. Previously, we reported increased expression of TDE_0259 (oxtR), which exhibits similarities with the multiple-antibiotic resistance regulator (marR)-like gene in the bacteriocin ABC transporter gene-deficient mutant, which altered susceptibility to antimicrobial agents. Therefore, we investigated the function of oxtR in T. denticola using an oxtR-deficient mutant. We observed increased OxtR expression upon oxygen exposure. The growth rate of the bacterium was unaffected by the inactivation of oxtR. We observed a relative increase in the expression of genes associated with iron-sulfur cluster-binding proteins, flavodoxin, oligopeptide/dipeptide ABC transporters, heat shock proteins, DNA helicase, iron compounds, ABC transporters, and lipoproteins. The oxtR mutant exhibited an increased minimum inhibitory concentration against ofloxacin. In addition, the mutant showed a slightly faster growth rate than that of the wild type under oxygen stress. Our findings also suggested that OxtR may regulate the operon by binding to a potential promoter region. The oxygen-sensing regulator oxtR plays a role in regulating the expression of a potential ferredoxin, which may contribute to the response to oxygen-induced stress in T. denticola. Comparison of 2 strains of T. denticola. Treponema denticola ATCC 35405 and NY-7 were cultured in TYGVS medium for 24-48 h. Profile of gene expression of T. denticola NY-7 was compared to that of ATCC 35405.