ABSTRACTAcylated amino acids function as important components of the cellular membrane in some bacteria. Biosynthesis is initiated by theN-acylation of the amino acid, and this is followed by subsequentO-acylation of the acylated molecule, resulting in the production of the mature diacylated amino acid lipid. In this study, we use both genetics and liquid chromatography-mass spectrometry (LC-MS) to characterize the biosynthesis and function of a diacylated glycine lipid (GL) species produced inBacteroides thetaiotaomicron. We, and others, have previously reported the identification of a gene, namedglsBin this study, that encodes anN-acyltransferase activity responsible for the production of a monoacylated glycine calledN-acyl-3-hydroxy-palmitoyl glycine (or commendamide). In all of theBacteroidalesgenomes sequenced so far, theglsBgene is located immediately downstream from a gene, namedglsA, that is also predicted to encode a protein with acyltransferase activity. We use LC-MS to show that the coexpression ofglsBandglsAresults in the production of GL inEscherichia coli. We constructed a deletion mutant of theglsBgene inB. thetaiotaomicron, and we confirm thatglsBis required for the production of GL inB. thetaiotaomicron. Moreover, we show thatglsBis important for the ability ofB. thetaiotaomicronto adapt to stress and colonize the mammalian gut. Therefore, this report describes the genetic requirements for the biosynthesis of GL, a diacylated amino acid species that contributes to fitness in the human gut bacteriumB. thetaiotaomicron.IMPORTANCEThe gut microbiome has an important role in both health and disease of the host. The mammalian gut microbiome is often dominated by bacteria from theBacteroidales, an order that includesBacteroidesandPrevotella. In this study, we have identified an acylated amino acid, called glycine lipid, produced byBacteroides thetaiotaomicron, a beneficial bacterium originally isolated from the human gut. In addition to identifying the genes required for the production of glycine lipids, we show that glycine lipids have an important role during the adaptation ofB. thetaiotaomicronto a number of environmental stresses, including exposure to either bile or air. We also show that glycine lipids are important for the normal colonization of the murine gut byB. thetaiotaomicron. This work identifies glycine lipids as an important fitness determinant inB. thetaiotaomicronand therefore increases our understanding of the molecular mechanisms underpinning colonization of the mammalian gut by beneficial bacteria.
Rags to riches: Amino acid sensing by the Rag GTPases in health and disease
