Large-scale mutant libraries of S. pyogenes serotype M18 and M49 were generated by transposon mutagenesis. Subsequently, mutants with an altered susceptibility to oxidative stress were selected and the transposon insertion site was analysed. This led to the identification of genes encoding for proteins involved in metabolic processes, for the synthesis and repair of DNA as well as for genes with unknown functions and intergenic regions.
For serotyp M49 multiple transposon mutants had a TnSpc insertion in the gene region Spy49_1658c with unknown function. The inactivation or deletion of Spy49_1658 increased the tolerance to O2.- produced by MS. Additionally, ΔSpy49_1658c showed a significantly reduced surface hydrophobicity compared to M49 591.
Experiments with human keratinocytes HaCaT showed a reduced capacity of ΔSpy49_1658c to adhere to HaCaT compared to the wild type strain. Furthermore, in the presence of HaCaT the rate of mortification or rate of growth inhibition of ΔSpy49_1658c was increased compared to the wild type strain. Growth experiments in human blood revealed a significantly reduced growth rate of S. pyogenes M49 due to the loss of Spy49_1658c.