Abstract
As a universal quorum sensing (QS) signal, autoinducer-2 (AI-2) is utilized by both Gram-negative and Gram-positive bacteria to coordinate several group behaviors, such as biofilm formation, virulence, and motility, when the bacterial cell density exceeds the thresholds. The determination of the AI-2 level is essential to understand the physiological and biochemical processes involved in bacterial communication. However, the current methods for AI-2 determination are complicated, time-consuming, and require costly equipment, such as a mass spectrometer (MS) or fluorescence detector (FLD). In this study, we present a new and easily applicable method for AI-2 determination. This method, based on the primary derivatization of AI-2 with 2,3-diaminonaphthalene (DAN), uses an affordable high-performance liquid chromatography (HPLC) instrument with a UV detector. Under optimized conditions, our method showed a good linearity (r2 = 0.999) and demonstrated the effective detection of AI-2 levels in various environmental samples, as follows: 0.38 (±0.05) μM for E. coli K12, 0.48 (±0.05) μM for Aeromonas sp. YB-2, 0.32 (±0.06) μM for the Enterobacter sp. YB-3, and 0.28 (±0.16) μM for activated sludge.
Highlights
Bacteria can sense the presence of, and communicate with, neighbors by detecting chemical signals called autoinducers
quorum sensing (QS) involves the regulation of gene expression, such as biofilm formation, dispersion, conjugation, virulence, symbiosis, motility, and morphology, in response to variations in bacterial cell density [1,2,3]
Three types of QS signaling molecules are known to be involved in bacterial communication—Gram-negative bacteria use N-acylhomoserine lactones (AHLs or HSLs), while Gram-positive bacteria use autoinducer peptides (AIPs) or oligopeptides
Summary
Bacteria can sense the presence of, and communicate with, neighbors by detecting chemical signals called autoinducers. Various methods, such as bioassay [11,12,13,14], high-performance liquid chromatography (HPLC) [15,16], liquid chromatography–mass spectrometry (LC–MS) [17,18], and gas chromatography–mass spectrometry (GC–MS) [19], have been developed for the analysis of AHLs, demonstrating that the detection of these molecules is relatively easy. One example of the second type is the widely applied AI-2 bioassay method that uses the bioluminescent response of an AI-2 reporter strain (e.g., Vibrio harveyi BB strains) to measure the intensity of the AI-2 signal.
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