Streptococcus parasanguinis Transcriptomics Data with and without Exogenous Nitrite

Oral commensal streptococci play a large role in mediating microbial homeostasis. Our published findings have demonstrated that hydrogen peroxide (H2O2) produced by oral commensal streptococci can react with salivary nitrite (NO2) and generate peroxynitrite (ONOO-), a potent antimicrobial. We have shown that the combinatorial antimicrobial effects of NO2 and H2O2 produced from the commensal Streptococcus parasanguinis, inhibit the colonization and pathogenesis of oral pathogens to promote homeostasis. Remarkably, S. parasanguinis is highly resistant to the NO2 and ONOO-. However, it remains unclear how S. parasanguinis copes in the presence of nitrosative stress. The goal of this study was to identify mechanisms used by S. parasanguinis to resist NO2-mediated nitrosative stress using a transcriptomics approach. Transcriptomic analysis showed that the competence response regulator, comE, is upregulated in the presence of NO2. Loss of comE resulted in a decrease in biofilm development, H2O2 production, increased acid tolerance and sensitivity to ONOO- compared to wild-type S. parasanguinis. Our data show that ComE is critical for key aspects of S. parasanguinis physiology and potentially impacts this commensal's ability to colonize and modulate homeostasis in the oral cavity. Overall design: Wild-type Streptococcus parasanguinis were grown in the presence of 2 mM of Nitrite in Todd-Hewitt Broth to late-exponential phase and RNA was harvested for RNA-sequencing analysis.