The Streptococcus pyogenes mannose phosphotransferase system (Man-PTS) influences antimicrobial activity and niche-specific nasopharyngeal infection

Abstract

Streptococcus pyogenes is a human-adapted pathogen that causes a variety of infections including pharyngitis and skin infections, and although this bacterium produces many virulence and host colonization factors, how S. pyogenes competes with the host microbiota is not well understood. Here we detected antimicrobial activity produced from S. pyogenes MGAS8232 that was able to prevent the growth of Micrococcus luteus. This activity was produced when cells were grown in 5% CO2 and in M17 media supplemented with galactose; however, evaluation of the phenotype with the addition of alternative sugars coupled with genome sequencing experiments revealed the antimicrobial phenotype was not related to classical bacteriocins. To further determine genes involved in the production of this activity, a transposon mutant library in S. pyogenes MGAS8232 was generated. The transposon screen identified the mannose phosphotransferase system (Man-PTS), a major sugar transporter in S. pyogenes, as important for the antimicrobial phenotype. Additional loss-of-function transposon mutants linked to the antimicrobial activity were identified to also be involved in alternative sugar utilization and additionally, the Man-PTS was also further identified from a secondary mutation in a bacteriocin operon mutant. Sugar utilization profiles in all the Man-PTS mutants demonstrated that galactose, mannose, and N-acetylglucosamine utilization was impaired in different Man-PTS mutants. In vitro RNA-seq experiments in high and low glucose concentrations further identified the Man-PTS as a glucose transporter; however, there was no transcriptional regulators or virulence factors affected with the loss of the Man-PTS. A clean deletion in the Man-PTS demonstrated defects in a mouse model of nasopharyngeal infection. Overall, the ability of S. pyogenes to utilize alternative sugars presented by glycans seems to play a role in acute infection and interactions with the endogenous microbial population existing in the nasopharynx. IMPORTANCEStreptococcus pyogenes causes a wide range of infections and is responsible for over 500,000 deaths per year due to invasive infections and post-infection sequelae. The most common clinical manifestation of S. pyogenes however are acute infections such as pharyngitis or impetigo. S. pyogenes can adapt to its environment through alternative sugar metabolism and in this study, we identified an antimicrobial phenotype that was not bacteriocin-related but a by-product of alternative sugar metabolism. Evidently, the mannose phosphotransferase system, a well-studied sugar transporter, was involved in production of the antimicrobial, and was also important for S. pyogenes to utilize alternative sugars and establish nasopharyngeal infection, but not skin infection. Overall, this study identified potential strategies used by S. pyogenes for interactions with the endogenous microbiota and further elucidated the importance of sugar metabolism in acute infection.