Identification of a glutathione transporter in A. actinomycetemcomitans

Abstract

ABSTRACT Bacteria rely on extracellular chemical cues to sense their environment, interact with one another, and shape their chemical landscape. Understanding this biochemistry can help us elucidate the mechanisms by which bacterial interactions impact community function. By applying mass spectrometry to mono- and co-cultures of the oral pathogen Aggregatibacter actinomycetemcomitans and the oral commensal Streptococcus gordonii , we identified hundreds of extracellular small molecules produced by these bacteria. We discovered that A. actinomycetemcomitans secretes millimolar amounts of glutathione and identified a five-gene operon (called gttABCDE ) that is important for maximum secretion. The metabolomics data set generated in this study provides a valuable data set for unraveling the importance of individual molecules for mediating polymicrobial interactions in the oral cavity. IMPORTANCE Microbes produce a large array of extracellular molecules, which serve as signals and cues to promote polymicrobial interactions and alter the function of microbial communities. This has been particularly well studied in the human oral microbiome, where key metabolites have been shown to impact both health and disease. Here, we used an untargeted mass spectrometry approach to comprehensively assess the extracellular metabolome of the pathogen Aggregatibacter actinomycetemcomitans and the commensal Streptococcus gordonii during mono- and co-culture. We generated and made publicly available a metabolomic data set that includes hundreds of potential metabolites and leveraged this data set to identify an operon important for glutathione secretion in A. actinomycetemcomitans .