Discovery of Complex Mixtures of Novel Long‐Chain Quorum Sensing Signals in Free‐Living and Host‐Associated Marine Alphaproteobacteria

Abstract

More than 100 bacterial isolates from various marine habitats were screened for AHL production by using gfp reporter constructs based on the lasR system of Pseudomonas aeruginosa and the luxR system of Vibrio fischeri. Of the 67 Alphaproteobacteria tested, most of which belonged into the so-called Roseobacter clade, 39 induced fluorescence in either one or both sensor strains up to 103-fold compared to controls. Acylated homoserine lactones were identified by GC-MS analysis and shown to have chain lengths of C8, C10, C13-C16, and C18. One or two double bonds were often present, while a keto or hydroxyl group occurred only rarely in the side chain. Most strains produced several different AHLs. C18-en-HSL and C18-dien-HSL were produced by Dinoroseobacter shibae, an aerobic anoxygenic phototrophic bacterium isolated from dinoflagellates, and are among the longest AHLs found to date. Z7-C14-en-HSL, which has previously been detected in Rhodobacter sphaeroides, was produced by Roseovarius tolerans and Jannaschia helgolandensis. This signal molecule was synthesised and shown to induce a similar response to the culture supernatant in the respective sensor strain. The widespread occurrence of quorum-sensing compounds in marine Alphaproteobacteria, both free-living strains and those associated to eukaryotic algae, points to a great importance of this signalling mechanism for the adaptation of the organisms to their widely different ecological niches.

Signaling-mediated cross-talk modulates swarming and biofilm formation in a coral pathogen Serratia marcescens

“…This lack of complexity in QS signal profiles of the tested bacteria is different from the reports, in which a-and g-proteobacterial associates of sponges and marine dinoflagellates were shown to produce multiple AHLs, including signals with unusually long acyl side chains (Wagner-Dobler et al, 2005;Mohamed et al, 2008). Treatment with the AHL lactonase AiiA, significantly reduced appearance of the detectable TLC spots produced by the Marinobacter sp.…”

“…The ability of marine prokaryotes and eukaryotes to excrete compounds that stimulate or inhibit QS reporters is now well documented (Pasmore and Costerton, 2003;Wagner-Dobler et al, 2005;Skindersoe et al, 2008;Teasdale et al, 2009;Kwan et al, 2010); however, ecological roles of these compounds and of the bacteria that produce them are less understood. Therefore, our subsequent experiments focused on testing the behaviors of the isolates in the dual-species microbial consortia consisting of the coral pathogen S. marcescens PDL100 and the isolate of interest.…”

You are what you talk: quorum sensing induces individual morphologies and cell division modes in Dinoroseobacter shibae

“…Deletion of luxI 1 completely eliminates AHL production in D. shibae Previously it had been shown that D. shibae synthesizes C18en-HSL and C18dien-HSL in MB medium (Wagner-Dö bler et al, 2005. This was now also confirmed in the minimal medium used for microarray analyses by GC-MS (Supplementary Figure S2).…”

“…shibae, like many other Proteobacteria, relies on acylated homoserine-lactones (AHLs) for cell-tocell communication. It produces C18en-HSL and C18dien-HSL with one and two unsaturations in the acyl side chain, respectively, which represent novel structures not described in any other bacterial species so far (Wagner-Dö bler et al, 2005). Genome analysis of D. shibae revealed the presence of three LuxI type AHL synthase genes (termed luxI 1 , luxI 2 , luxI 3 ).…”

Rhizobial homologs of the fatty acid transporter FadL facilitate perception of long-chain acyl-homoserine lactone signals

“…S. meliloti produces a variety of longchain AHLs, including C18-, C16:1-, 3-oxo-C16:1-, 3-oxo-C14-, and C12-HSLs (8,9). AHLs with an acyl chain containing 14 or more carbons may be characteristic of α-proteobacteria, being identified in Rhodobacter capsulatus, Agrobacterium vitis, and several distant marine species as well (10)(11)(12). S. meliloti strains 1021 and 2011 have a single AHL-based QS system (Fig.…”