PgRsp Is a Novel Redox-Sensing Transcription Regulator Essential for Virulence.

is one of the etiological agents of chronic periodontitis. Both heme and oxidative stress impact expression of genes responsible for its survival and virulence. Previously we showed that ferric uptake regulator homolog affects expression of a gene encoding a putative Crp/Fnr superfamily member, termed redox-sensing protein (PgRsp). Although PgRsp binds heme and shows the highest similarity to proteins assigned to the CooA family, it could be a member of a novel, separate family of proteins with unknown function. Expression of the gene is autoregulated and iron/heme dependent. Genes encoding proteins engaged in the oxidative stress response were upregulated in the mutant (TO11) strain compared with the wild-type strain. The TO11 strain showed higher biomass production, biofilm formation, and coaggregation ability with and . We suggest that PgRsp may regulate production of virulence factors, proteases, Hmu heme acquisition system, and FimA protein. Moreover, we observed growth retardation of the TO11 strain under oxidative conditions and decreased survival ability of the mutant cells inside macrophages. We conclude that PgRsp protein may play a role in the oxidative stress response using heme as a ligand for sensing changes in redox status, thus regulating the alternative pathway of the oxidative stress response alongside OxyR.