Dpr-mediated h2o2 resistance contributes to streptococci survival in a cystic fibrosis airway model system

The cystic fibrosis (CF) lung environment is conducive to the colonization of bacteria as polymicrobial biofilms, which are associated with poor clinical outcomes for persons with CF (pwCF). Streptococcus spp. is highly prevalent in the CF airway, but its role in the CF lung microbiome is poorly understood. Some studies have shown Streptococcus spp. to be associated with better clinical outcomes for pwCF, while others show that high abundance of Streptococcus spp. is correlated with exacerbations. Our lab previously reported a polymicrobial culture system consisting of four CF-relevant pathogens that can be used to study microbial behavior in a more clinically relevant setting. Here, we use this model system to identify genetic pathways that are important for Streptococcus sanguinis survival in the context of the polymicrobial community. We identified genes related to reactive oxygen species (ROS) as differentially expressed in S. sanguinis monoculture versus growth of this microbe in the mixed community. Genetic studies identified Dpr as important for S. sanguinis survival in the community. We show that Dpr, a DNA binding ferritin-like protein, and PerR, a peroxide-responsive transcriptional regulator of Dpr, are important for protecting S. sanguinis from phenazine-mediated toxicity in co-culture with P. aeruginosa and when exposed to ROS, both of which mimic the CF lung environment. Characterizing such interactions in a clinically relevant model system contributes to our understanding of microbial behavior in the context of polymicrobial biofilm infections. IMPORTANCE Streptococcus spp. is recognized as a highly prevalent pathogen in CF airway infections. However, its role in clinical outcomes for pwCF is poorly understood. Here, we leverage a polymicrobial community system previously developed by our group to model CF airway infections as a tool to investigate a Pseudomonas-Streptococcus interaction involving ROS. We show that protection against ROS is required for S. sanguinis survival in a clinically relevant polymicrobial system. Using this model system to study interspecies interactions contributes to our broader understanding of the complex role of Streptococcus spp. in the CF lung. ### Competing Interest Statement The authors have declared no competing interest.