Study identifies genetic mechanisms of amino acid toxicity in Staphylococcus aureus, suggests glycine as antibiotic adjuvant
Researchers used deep transposon insertion sequencing to map the genetic mechanisms that allow Staphylococcus aureus to tolerate toxic concentrations of glycine and L-serine. The study found that intracellular accumulation of counterbalancing amino acids—particularly alanine—is the primary resistance mechanism, with specific transporters playing key roles. The findings suggest glycine could be used as an adjuvant to enhance existing antibiotics like D-cycloserine against S. aureus infections.
A study published on bioRxiv used genome-wide transposon insertion sequencing (Tn-seq) to identify genes required for Staphylococcus aureus to survive exposure to excess glycine, diglycine, and L-serine. The central finding is that bacteria resist amino acid toxicity primarily by accumulating counterbalancing amino acids intracellularly, with alanine serving this role against glycine excess. Key transporters were identified as critical for fitness: the peptide transporter DtpT was essential under both L-serine and glycine stress, while the alanine transporter AapA was specifically required under diglycine conditions. The cystine/cysteine transporter TcyABC was also implicated in L-serine tolerance, suggesting multiple uptake pathways contribute to resistance. Mechanistically, excess glycine was found to inhibit alanine uptake, explaining why the D-alanine synthesis enzyme Dat becomes essential under glycine stress. Capitalizing on this vulnerability, the researchers demonstrated strong synergy between glycine and D-cycloserine—an alanine analog antibiotic—in inhibiting S. aureus growth, raising the prospect of using the biocompatible and inexpensive amino acid glycine as an antibiotic adjuvant.
What's missing
As a preprint, this study has not yet undergone peer review, so findings should be interpreted with caution. The study does not report in vivo or animal model data, leaving open whether glycine-D-cycloserine synergy translates to efficacy in living systems. The clinical relevance, effective dosing, and potential toxicity of high-concentration glycine in human therapeutic contexts are not addressed.
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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