A Commensal Streptococcus Dysregulates the Pseudomonas aeruginosa Denitrification Pathway

Chronic infections in the cystic fibrosis (CF) airway are composed of both pathogenic and commensal bacteria. Chronic Pseudomonas aeruginosa infections are the leading cause of lung deterioration in CF. Interestingly, oral commensals can translocate to the CF lung and their presence is associated with improved lung function, presumably due to their ability to antagonize P. aeruginosa. We have previously shown that one commensal, Streptococcus parasanguinis, produces hydrogen peroxide that reacts with nitrite to generate reactive nitrogen intermediates (RNI) which inhibit P. aeruginosa growth. In this study, we sought to understand the global impact of commensal-mediated RNI on the P. aeruginosa transcriptome. P. aeruginosa was grown in the presence or absence of nitrite, S. parasanguinis, or both nitrite and S. parasanguinis, and RNA sequencing was performed to assess gene expression between treatment and control groups.