Study identifies genetic mechanisms of amino acid toxicity in Staphylococcus aureus, suggests glycine as antibiotic adjuvant
Researchers used transposon insertion sequencing to identify genes that allow S. aureus to tolerate excess glycine and L-serine, finding that counterbalancing amino acids like alanine are key to resistance. The study reveals that specific amino acid transporters and the enzyme D-alanine aminotransferase are essential for survival under these conditions. The findings suggest glycine combined with existing antibiotics could offer a new treatment strategy against this dangerous pathogen.
A bioRxiv preprint describes experiments using deep transposon insertion sequencing (Tn-seq) to map genes required for Staphylococcus aureus to survive in high concentrations of glycine and L-serine. The researchers found that intracellular accumulation of counterbalancing amino acids—particularly alanine in response to excess glycine—is the primary resistance mechanism. Multiple amino acid and peptide transporters proved essential for fitness under these conditions, including the peptide transporter DtpT (required for L-serine and glycine tolerance) and the alanine transporter AapA (essential for diglycine tolerance). The enzyme D-alanine aminotransferase (Dat) was also necessary for glycine tolerance. Notably, the team demonstrated strong synergistic inhibition of S. aureus growth when combining glycine with D-cycloserine, an existing alanine analog antibiotic, suggesting a potential new combination therapy approach.
What's missing
The study's own limitations are not detailed in the provided abstract. Typical caveats for Tn-seq studies include: whether results were validated in independent mutant strains; whether findings translate to in vivo infection models; the specific glycine and L-serine concentrations tested and their physiological relevance; and whether the synergy with D-cycloserine was tested in animal models or clinical contexts.
What different sources said
- bioRxivCenter
Genetic basis of glycine and L-serine toxicity in Staphylococcus aureus and the case for glycine as an antibiotic adjuvant
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