Project description:Transcriptional profiling of Streptococcus pyogenes MGAS5005 cells comparing control untreated GAS cells with GAS cells exposed to 4uM heme for 1.5 h
Project description:Transcriptional profiling of Streptococcus pyogenes MGAS5005 cells comparing control untreated GAS cells with GAS cells exposed to 4uM heme for 1.5 h Two-condition experiment, untreated vs. heme-treated MGAS5005 cells. Biological replicates: 3 control, 3 Heme-treated, independantly grown and harvested. One replicate per array.
Project description:The nasopharynx and the skin are the major oxygen-rich anatomical sites for colonization by the human pathogen Streptococcus pyogenes (group A Streptococcus, GAS). To establish infection, GAS must survive oxidative stress generated during aerobic metabolism and the release of reactive oxygen species (ROS) by host innate immune cells. Glutathione is the major host antioxidant molecule while GAS is glutathione-auxotrophic. Here we report the molecular characterization of the ABC transporter substrate binding protein GshT in the GAS glutathione salvage pathway. We demonstrate that glutathione uptake is critical for aerobic growth of GAS and that impaired import of glutathione induces oxidative stress that triggers enhanced production of the reducing equivalent NADPH. Our results highlight the interrelationship between glutathione assimilation, carbohydrate metabolism, virulence factor production and innate immune evasion. Together, these findings suggest an adaptive strategy employed by extracellular bacterial pathogens to exploit host glutathione stores for their own benefit.
Project description:A new variant of group A Streptococcus (GAS) serotype M1 (designated ‘M1UK’) has been reported in the United Kingdom, linked with seasonal scarlet fever surges, marked increase in invasive infections, and exhibiting enhanced expression of the superantigen SpeA. The progenitor GAS ‘M1global’ and M1UK clones can be differentiated by 27 SNPs and 4 indels, yet the mechanism for speA upregulation is unknown. Here we investigate the previously unappreciated expansion of M1UK in Australia, now isolated from the majority of serious infections caused by serotype M1 GAS. M1UK sub-lineages circulating in Australia also contain a novel toxin repertoire associated with epidemic scarlet fever causing GAS in Asia. A single SNP in the M1UK tmRNA gene ssrA drives enhanced SpeA superantigen expression as a result of ssrA terminator readthrough in the M1UK lineage. This represents a new paradigm of toxin expression and urges enhanced international surveillance.
