Identification of bacterial N-acylhomoserine lactones (AHLs) with a combination of ultra-performance liquid chromatography (UPLC), ultra-high-resolution mass spectrometry, and in-situ biosensors

Abstract

N-Acylated homoserine lactones (AHLs) are produced by Gram-negative bacteria as communication signals and are frequently studied as mediators of the "quorum sensing" response of bacterial communities. Several reports have recently been published on the identification of AHLs from different species and attempts have been made to study their role in natural habitats, for example the surface of plant roots in the rhizosphere. In this article, different analytical methods, including bacterial biosensors and chromatographic techniques, are reviewed. A concept for assignment of the structures of AHLs is also presented. The retention behaviour of derivatives of AHLs containing beta-keto or hydroxyl groups and/or double bonds has been evaluated in relation to the separation behaviour of AHLs with saturated and unsubstituted alkanoyl chains. Samples have also been analysed by high resolution mass spectrometry (Fourier-transform ion-cyclotron-resonance mass spectrometry, FTICR-MS), nano liquid chromatography-electrospray ionization ion trap mass spectrometry (nano-LC-MS) and by the aid of a biosensor. The results obtained from ultra performance liquid chromatography (UPLC), FTICR-MS, nano-LC-MS, and bioassays have been compared to attempt structural characterisation of AHL without chemical synthesis of analytical standards. The method was used to identify the major AHL compound produced by the rhizosphere bacterium Acidovorax sp. N35 as N-(3-hydroxydecanoyl)homoserine lactone.

Microbial interactions associated with biofilms attached to Trichodesmium spp. and detrital particles in the ocean

“…Ethyl acetate and dichloromethane are commonly used as extraction solvents for AHLs (reviewed in Fekete et al, 2007). However, ethyl acetate has been shown to be a more effective solvent and is improved further by slight acidification by 0.1% formic acid (Ravn et al, 2001).…”

“…This density is not uncommon in biofilms; not only do biofilms host high densities of bacteria, but they also offer a physical barrier to prevent the diffusive loss of AHLs into seawater. Within biofilms, AHL concentrations are maintained at significantly higher concentrations (up to four orders of magnitude) than occur in the external environment Fekete et al, 2007). In addition to deterring the diffusive loss of AHLs, the chemical environment within biofilms is typically more acidic than the surrounding environment (Vroom et al, 1999) which will have a stabilizing effect on AHLs by reducing the rate of abiotic base-catalyzed lactonolysis.…”

Cell–Cell Communication in Azospirillum and Related PGPR

“…According to the molecular ion peaks and fragments, the molecular mass and structural features can be estimated. MS detects even picomoles of samples and can be combined with HPLC (Winson et al 1995 ), gas chromatography (GC) (Zhang et al 1993 ;Wagner-Dobler et al 2005 ), UPLC (Li et al 2006 ;Fekete et al 2007 ), nano-LC (Fekete et al 2007 ), and capillary zone electrophoresis (CZE-MS) (Frommberger et al 2005 ). There are many types of ionization available, the most commonly used for AHLs being (reviewed in Wang et al 2010 ) electron ionization (EI-MS) (Bainton et al 1992 ), fast atom bombardment (FAB-MS) (Pearson et al 1995 ;Winson et al 1995 ), chemical ionization (CI-MS) (Gray et al 1996 ), electrospray ionization (ESI-MS) (Morin et al 2003 ), and atmospheric pressure chemical ionization (APCI-MS) (Vial et al 2006 ).…”

Detection and Control of Indoor Airborne Pathogenic Bacteria by Biosensors Based on Quorum Sensing Chemical Language: Bio-Tools, Connectivity Apps and Intelligent Buildings

“…Several analytical methods have been used to identify these molecules, like ultra-performance liquid chromatography (UPLC), high-performance liquid chromatography (HPLC) and highresolution mass spectrometry; nevertheless, these chemical analyses require high-tech equipment as well as sample preparation, extraction and purification [39]. Therefore, it has been proposed that QS microbial biosensors are a potent tool for environmental and healthcare monitoring [40].…”