Investigating the mechanism of a novel glycine dependent riboswitch and a putative non coding regulatory RNA in Streptococcus pyogenes We investigated gene expression regulation by a putative glycine(Gly) riboswitch located in the 5′ UTR of a SAF protein gene in the S.pyogenes. Gly dependency was studied using a luciferase reporter gene system. Maximal reporter gene expression happened in the presence of low Gly concentrations. RT qPCR showed that in the presence of Gly (≥1 mM) expression of the gene was downregulated. Growth in the presence of 0.1 mM Gly led to the production of a full length transcript. We conclude that the Gly riboswitch in S. pyogenes represses gene expression in the presence of high Gly concentrations.<eng>