Abstract
This study presents a fast, accurate and sensitive technique using gas chromatography-mass spectrometry (GC-MS) for the identification and quantification of N-acyl homoserine lactones (AHLs) in the extracts of bacterial strain of Pseudomonas aeruginosa and sputum sample of a cystic fibrosis patient. This method involves direct separation and determination of AHLs by using GC-MS as simultaneous separation and characterization of AHLs were possible without any prior derivatiza-tion. Electron ionization resulted in a common fragmentation pattern with the most common fragment ion at m/z 143 and other minor peaks at 73, 57 and 43. The limit of detection for N-butanoyl, N-hexanoyl, N-octanoyl, N-decanoyl, N-dodecanoyl and N-tetradecanoyl homoserine lactones was 2.14, 3.59, 2.71, 2.10, 2.45 and 2.34 µg/L, respectively. The presence of AHLs in the culture of P. aeruginosa strain and spu-tum of a cystic fibrosis patient was achieved in selected ion monitoring (SIM) mode by using the prominent fragment at m/z 143.
Highlights
N-acyl homoserine lactones (AHLs) are important intercellular signaling molecules used by many bacteria to monitor their population density and control a variety of physiological functions in a cell-density-dependent manner by the process called quorum sensing
Detection was performed in selected ion monitoring (SIM) mode by using fragment at m/z 143
A primary aspect of this work is to establish an assay for analyzing the AHLs from bacterial cultures and sputum samples
Summary
N-acyl homoserine lactones (AHLs) are important intercellular signaling molecules used by many bacteria to monitor their population density and control a variety of physiological functions in a cell-density-dependent manner by the process called quorum sensing. Quorum sensing involves synthesis and detection of extra cellular signals termed as auto inducers. Many Gram-negative bacteria like Pseudomonas aeruginosa, Vibrio fischeri, Agrobacterium tumefaciens etc., use acyl homoserine lactones (AHLs) as cell-cell communication molecules. When a threshold bacterial density (and corresponding AHL concentration) is reached, AHLs interact with transcriptional activators to trigger the expression of target genes. Members of the LuxI family of proteins synthesize these signals. These signal molecules diffuse from bacterial cells and accumulate in the medium as a function of cell growth
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