Profiling acylated homoserine lactones in Yersinia ruckeri and influence of exogenous acyl homoserine lactones and known quorum-sensing inhibitors on protease production

Abstract

Aims: To profile the quorum‐sensing (QS) signals in Yersinia ruckeri and to examine the possible regulatory link between QS signals and a typical QS‐regulated virulence phenotype, a protease. Methods and Results: Liquid chromatography‐high resolution mass spectrometry (HPLC‐HRMS) showed that Y. ruckeri produced at least eight different acylated homoserine lactones (AHLs) with N‐(3‐oxooctanoyl)‐l‐homoserine lactone (3‐oxo‐C8‐HSL) being the dominant molecule. Also, some uncommon AHL, N‐(3‐oxoheptanoyl)‐l‐homoserine lactone (3‐oxo‐C7‐HSL) and N‐(3‐oxononanoyl)‐l‐homoserine lactone (3‐oxo‐C9‐HSL), were produced. 3‐oxo‐C8‐HSL was detected in organs from fish infected with Y. ruckeri. Protease production was significantly lower at temperatures above 23°C than below although growth was faster at the higher temperatures. Neither addition of sterile filtered high‐density Y. ruckeri culture supernatant nor the addition of pure exogenous AHLs induced protease production. Furthermore, three QS inhibitors (QSIs), sulfur‐containing AHL analogues, did not inhibit protease production in Y. ruckeri. Conclusions: Exogenous AHL or sulfur‐containing AHL analogues did not influence the protease production indicating that protease production may not be QS regulated in Y. ruckeri. Significance and Impact of the Study: The array of different AHLs produced indicates that the QS system of Y. ruckeri is complex and could involve several regulatory systems. In this case, neither AHLs nor QSI would be likely to directly affect a QS‐regulated phenotype.

Quorum Sensing Activity of Hafnia alvei Isolated from Packed Food

“…It is, however, often detected and most intensively studied in plant-associated bacteria [24–26]. Presence of this molecule has been linked to the virulence genes in Pseudomonas aeruginosa , an opportunistic human pathogen [27], as well as Yersinia ruckeri , a fish pathogen [28]. Whether 3-oxo-C8-HSL has a role in pathogenesis of H. alvei FB1, and it contributes to the survival or colonization of the strain in its environment of origin, remain questions to be solved in more in-depth studies.…”

Potential Emergence of Multi-quorum Sensing Inhibitor Resistant (MQSIR) Bacteria

“…Putative role in pathogenesis [107,108] a Quorum sensing system Qrr sRNAs, which consequently regulates the QSS (Table 2) [47,48]. In the marine bacterium Vibrio harveyi, QSS-LuxMLuxN system, responds to AHL signal harveyi autoinducer-1(HAI-1), synthesized by LuxLM, which is recognized by the harveyi autoinducer-1sensor (HAI-1 sensor), Lux N [49][50][51].…”

“…The QS signals modulating these QSS range from unsubstituted-to substituted-HSLs, as well as peptides (DKPs), quinolones, hormones [69,[94][95][96][97][98][99][100][101][102][103][104][105]. In Yersinia, luxI/R homologues are majorly regulated by substituted AHLs [106][107][108].…”

Characterization of <i>N</i>-acyl homoserine lactones (AHLs) producing bacteria isolated from vacuum-packaged refrigerated turbot (<i>Scophthalmus maximus</i>) and possible influence of exogenous AHLs on bacterial phenotype

“…Proteolytic activity was determined using azocasein as the substrate according to the method described by Gram et al (2002) with some modifications. Briefly, bacterial strains were inoculated into 100 mL LB broth in the absence or presence of exogenous AHLs (C4-HSL, C6-HSL, 3-oxo-C6-HSL, final concentration of 10 µM) (Kastbjerg et al, 2007). QS inhibitor (BMF), final concentration of 5.4 mg/L, that have no effect on the growth of the two bacterial strains were also used.…”