Deciphering Bacterial Universal Language by Detecting the Quorum Sensing Signal, Autoinducer-2, with a Whole-Cell Sensing System

Abstract

Bacteria communicate with neighboring bacteria of the same species or of other species by means of chemical signaling molecules. The concentration of such signaling molecules is proportional to the bacterial population size; upon reaching a threshold concentration, corresponding to a threshold cell density, certain specialized genes are expressed. This system of communication among bacteria is known as quorum sensing (QS). QS regulates diverse behaviors, such as formation of biofilms and production of pathogenic factors. Autoinducer-2 (AI-2) is a QS signaling molecule that is used for interspecies communication by both Gram-positive and Gram-negative bacteria. Bacteria are known to play an important role in many diseases, from infections to chronic inflammation. Therefore, QS is involved in a variety of disorders of bacterial origin or where bacteria play a crucial pathogenic role. One such condition is inflammatory bowel disease (IBD), a chronic inflammation of the gastrointestinal (GI) tract that includes debilitating diseases, such as ulcerative colitis (UC) and Crohn's disease (CD). To date, noninvasive methods are unavailable for the diagnosis and monitoring of IBD. We hypothesized that detection of QS molecules in physiological samples, specifically saliva and stool specimens, would provide with a method for the noninvasive, early diagnosis and monitoring of IBD conditions. To that end, we developed and optimized a whole-cell sensing system for AI-2, which is based on Vibrio harveyi strain BB170. Furthermore, we standardized and applied the biosensing system for the quantitative detection of AI-2 in saliva, stool, and intestinal samples from IBD patients.

Peptides as Quorum Sensing Molecules: Measurement Techniques and Obtained Levels In vitro and In vivo

“…Dose-response curves were obtained using 50 nM–0.5 mM dilutions of synthetic autoinducer-2 in saliva or stool matrix. The autoinducer-2 concentration was quantified in stool ( n = 2, 2.76 μM), ileal washing samples ( n = 1; 2.29 μM) and saliva from patients with IBD ( n = 3, 2.05 μM) and saliva from healthy volunteers ( n = 3; 1.39 μM) (Raut et al, 2013). …”

Bacterial Autoinducer-2 Detection via an Engineered Quorum Sensing Protein

“…The presence of AI-2 in saliva was also demonstrated in another study using a whole-cell biosensing system. 32 Analysis of additional samples is necessary to potentially establish the method developed herein as an analytical tool for detection of AI-2 to be employed in the diagnosis and monitoring of bacterial-related conditions.…”

Autoinducer-2 of gut microbiota, a potential novel marker for human colorectal cancer, is associated with the activation of TNFSF9 signaling in macrophages

“…A total of 312 samples (stool, tissue, saliva and serum samples) were collected and processed as described in previous studies. 28,29 Clinicopathological data were acquired according to hospital records. Informed consent was obtained from all participants, and the study was approved by the review board of the Affiliated Hospital of North Sichuan Medical College (Nanchong, China).…”

“…Vibrio harveyi (V. harveyi) strain BB170 was purchased from the Guangdong culture collection center and used to detect AI-2. Autoinducer bioassay (AB) media was prepared for culturing of cells and used for bioluminescence assays as described by Nilesh et al 28 F. nucleatum strains F01 were isolated from CRC tissues and confirmed in our previous study. 30…”

“…The concentration of AI-2 in each sample was calculated according to their bioluminescence value. 28 Purification of F. nucleatum (F01) AI-2…”