Abstract
In our search for quorum-sensing (QS) disrupting molecules, 75 fungal isolates were recovered from reef organisms (endophytes), saline lakes and mangrove rhizosphere. Their QS inhibitory activity was evaluated in Chromobacterium violaceum CVO26. Four strains of endophytic fungi stood out for their potent activity at concentrations from 500 to 50 μg mL−1. The molecular characterization, based on the internal transcribed spacer (ITS) region sequences (ITS1, 5.8S and ITS2) between the rRNA of 18S and 28S, identified these strains as belonging to four genera: Sarocladium (LAEE06), Fusarium (LAEE13), Epicoccum (LAEE14), and Khuskia (LAEE21). Interestingly, three came from coral species and two of them came from the same organism, the coral Diploria strigosa. Metabolic profiles obtained by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) suggest that a combination of fungal secondary metabolites and fatty acids could be the responsible for the observed activities. The LC-HRMS analysis also revealed the presence of potentially new secondary metabolites. This is, to the best of our knowledge, the first report of QS inhibition by marine endophytic fungi.
Highlights
Quorum sensing (QS) is the term coined to describe the process of cell-to-cell communication in bacteria
Fungi are a renowned source of bioactive compounds, their ability to thwart bacterial cell-to-cell communication is poorly characterized
Among the diversity of aquatic environments screened in this study, marine endophytes clearly stood out
Summary
Quorum sensing (QS) is the term coined to describe the process of cell-to-cell communication in bacteria. This intercellular communication enables the execution of coordinated behaviors in function of the bacterial population density. The process relies on the production, release and reception of signaling molecules that have been often classified into three main chemical categories: N-acyl homoserine lactones (AHLs), referred as “autoinducer-1” (AI-1), which are characteristic of. The most recent example are pyrones, recently identified as QS signals in Photorhabdus luminescens [4,5]. This likely represents only a small proportion of the extracellular metabolites involved in QS signaling Other chemically different signaling molecules have been identified over the last decades, such as the A-factor from Streptomyces (a γ-butyrolactone), 4-quinolones (Pseudomonas Quinolone Signal, PQS) or fatty acids (Diffusible Signal Factors, DSF) [2,3].
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