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 can cause multiple diseases, including pharyngitis and skin infections. Although this bacterium produces many virulence factors, how S. pyogenes competes with the host microbiota is not well understood. Here, we detected antimicrobial activity from S. pyogenes MGAS8232 that prevented the growth of Micrococcus luteus. This activity was produced when cells were grown in 5% CO₂ in M17 media supplemented with galactose; however, the addition of alternative sugars coupled with genome sequencing experiments revealed that 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 identified the mannose phosphotransferase system (Man-PTS), a major sugar transporter, as important for the antimicrobial phenotype. 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 further identified from an inadvertent secondary mutation in a bacteriocin operon mutant. Sugar utilization in the Man-PTS mutants demonstrated that galactose, mannose, and N-acetylglucosamine utilization was impaired. RNA-seq experiments in high and low glucose concentrations further characterized the Man-PTS as a glucose transporter; however, transcriptional regulators or virulence factors were not affected with the loss of the Man-PTS. Deletion of Man-PTS demonstrated defects in a mouse model of nasopharyngeal infection but not skin infection. This work suggests that the ability of S. pyogenes to utilize alternative sugars presented by glycans may play a role in acute infection and interactions with the endogenous microbial population existing in the nasopharynx.IMPORTANCEStreptococcus pyogenes is responsible for over 500,000 deaths per year primarily due to invasive infections and post-infection sequelae, although the most common manifestations include pharyngitis and impetigo. S. pyogenes can adapt to its environment through alternative sugar metabolism. Here, we identified an antimicrobial phenotype that was not bacteriocin-related but a by-product of alternative sugar metabolism. The mannose phosphotransferase system was involved in the 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 upper respiratory tract infection.