Chromatography of Quorum Sensing Peptides: An Important Functional Class of the Bacterial Peptidome

Quorum sensing is the process by which bacteria communicate with each other to regulate the expression of certain genes in a cell density-dependent manner. One group of signalling molecules used in this process are the quorum sensing peptides, which are primarily produced by Gram-positive bacteria. Aside from their known role in bacterial physiology, it was recently found that these peptides are also able to influence human cells in a direct or indirect manner. To fully elucidate their biological and clinical significance in the microbiome, the ability to detect and quantify these active peptides in cell media and in vivo is of utmost importance. Several different methods, primarily for bacterial cell culture media, have already been developed. Standard procedure employs traditional techniques such as solid-phase extraction during sample preparation, a critical step in the analysis. A suitable sample preparation to extract the entire peptidome, prior to untargeted mass spectrometry detection, has not yet been proposed. Following sample preparation, liquid chromatography is coupled with different detection methods with mass spectrometry as the most commonly used. The aim of this review is to summarise and critically discuss current analytical methods for quorum sensing peptide identification and quantification.