Streptococcus pyogenes is a major human-restricted pathogen capable of both localized and systemic diseases, as well as causing post-infectious acute and chronic rheumatological conditions. Despite its well-documented clinical importance and over a century of extensive research, gaps persist in understanding this pathogen. We report the discovery of a novel pigment produced by S. pyogenes when cultured in a replete, chemically defined medium. Color development accumulates during growth, requires exposure to oxygen, and remains associated with the bacterial cell. Though only 20% of a small strain collection produced the pigment (8 of 40), positive cultures were overrepresented by M1 and M89 serotypes. Given that pigments are critical virulence and fitness determinants in pathogens like Staphylococcus aureus and Streptococcus agalactiae, here we describe initial attempts to characterize S. pyogenes pigment biosynthesis, regulation, and potential benefits to the organism. 20,405 transposon mutants were screened for pigment loss in liquid culture, and we identified 94 independent hits enriched in pathways associated with isoprenoid biosynthesis, purine biosynthesis, guanosine transport, and mixed acid fermentation. Although color development requires oxygen, the extracted pigment did not provide antioxidative activity as compared to non-pigmented extracts. Pigment production was inhibited when the Rgg2/Rgg3 quorum-sensing system was active, though by unknown means. Treatment of RAW-Blue macrophages with the extracted pigment significantly reduced NF{kappa}B activation, suggesting a potential anti-inflammatory effect. Overall, this study describes a previously uncharacterized pigment produced by Streptococcus pyogenes and provides insights into its oxygen-dependent production and associated metabolic pathways.
Pathak, S. J., DeVinney, T., Gogos, A., Woods, R. A., Anderson, C. J., Chang, J. C., Federle, M. J.
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