Biosensors for Quorum Chemical Signaling Molecules: Implications of Bacterial Communication in Gastrointestinal Disorders

Abstract

The role of bacteria in causing biofouling and a wide variety of health imbalances has been long established. Moreover, bacterial load plays a fundamental role in these processes. Bacteria regulate expression of certain specialized genes, including certain behaviors/phenotypes, as a function of their population density. They employ chemical language, i.e., signaling molecules for their communication and group-based coordination. This phenomenon is known as quorum sensing (QS). The signaling molecules generally are N-acylated homoserine lactones (AHLs) in Gram-negative bacteria, small peptides in Gram-positive bacteria and a turanosyl borate diester, which is common to both types of bacteria. Thus, to better elucidate the mechanism of pathogenicity in bacteria, it is important to understand bacterial communication. The first step toward that end is to be able to detect the signaling molecules in a sensitive and selective manner. We hypothesize that the levels of these quorum sensing molecules (QSMs) in individuals may correlate with their health status, thus QSMs may be significant as biomarkers of diseases. These biomarkers may serve in the monitoring of disease activity and a patient's health. In that regard, we have developed whole-cell sensing systems for the detection of AHLs. Further, we employed these sensing systems in the analysis of biological samples. Specifically, we detected AHLs in biological matrixes, such as saliva and stool, of healthy subjects as well as patients with gastrointestinal (GI) disorders. We envision that these whole-cell sensing systems will allow for the monitoring of bacterial activity in biological fluids, and, consequently, the management of a patient's health. In addition, the aforementioned QS biosensing systems could be employed in the screening of potential anti-microbial drugs that interfere with bacterial communications. Furthermore, the method is non-invasive, fast, and cost-effective and requires simple sample preparation, which makes it amenable for high throughput detection as well as for miniaturization.