Global and phylogenetic distribution of quorum sensing signals, acyl homoserine lactones, in the family of Vibrionaceae.

Bastian Barker Rasmussen,Kristian Fog Nielsen,Henrique Machado,Eva C Sonnenschein,Lone Gram,Jette Melchiorsen

doi:10.3390/md12115527

Abstract

Bacterial quorum sensing (QS) and the corresponding signals, acyl homoserine lactones (AHLs), were first described for a luminescent Vibrio species. Since then, detailed knowledge has been gained on the functional level of QS; however, the abundance of AHLs in the family of Vibrionaceae in the environment has remained unclear. Three hundred and one Vibrionaceae strains were collected on a global research cruise and the prevalence and profile of AHL signals in this global collection were determined. AHLs were detected in 32 of the 301 strains using Agrobacterium tumefaciens and Chromobacterium violaceum reporter strains. Ethyl acetate extracts of the cultures were analysed by ultra-high performance liquid chromatography-high resolution mass spectrometry (MS) with automated tandem MS confirmation for AHLs. N-(3-hydroxy-hexanoyl) (OH-C6) and N-(3-hydroxy-decanoyl) (OH-C10) homoserine lactones were the most common AHLs found in 17 and 12 strains, respectively. Several strains produced a diversity of different AHLs, including N-heptanoyl (C7) HL. AHL-producing Vibrionaceae were found in polar, temperate and tropical waters. The AHL profiles correlated with strain phylogeny based on gene sequence homology, however not with geographical location. In conclusion, a wide range of AHL signals are produced by a number of clades in the Vibrionaceae family and these results will allow future investigations of inter- and intra-species interactions within this cosmopolitan family of marine bacteria.

Highlights

Quorum sensing (QS) is a process induced by cell population density and allows bacteria to sense and act on their local environment, as well as, communicate both within and between species [1]
A. tumefaciens detects regular, 3-OH- and O-homoserine lactones (HLs) and is especially sensitive to longer chain acyl homoserine lactones (AHLs) (>C4) [34], while C. violaceum reacts to short chain AHLs (C4 to C8) [35]
To confirm as well as extend the current knowledge on the AHL detection ability of these strains in a standardized manner, pure standard solutions of C4, C6, C8, C10, C12, C14, C18, OH-C4, OH-C6, OH-C12, O-C4, O-C6, O-C8, O-C10, and O-C12 homoserine lactones were evaluated in both biomonitor assays in three 10-fold dilutions

Summary

Introduction

Quorum sensing (QS) is a process induced by cell population density and allows bacteria to sense and act on their local environment, as well as, communicate both within and between species [1]. The essence underlying the mechanism of QS is based on the production and accumulation of signalling molecules called autoinducers. When the threshold concentration of the signals is reached, they bind to receptor proteins that act as either transcriptional activators or repressors [2]. The QS signals are small molecules such as acyl homoserine lactones (AHLs) produced by Gram-negative bacteria, autoinducer-2 (AI-2) used by Gram-negative and Gram-positive bacteria and oligopeptides which are utilized by Gram-positive bacteria [1,3]. Vibrionaceae is a large family of Gram-negative marine, facultative anaerobic bacteria belonging to the Gammaproteobacteria. This family includes several genera of which the largest are Vibrio and Photobacterium that include human and fish pathogens such as Vibrio cholerae, V. anguillarum, and

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