Abstract
A wide range of microbial symbionts such as bacteria and fungi colonize the tissues of macrophytes. The chemical interactions between these endophytes remain underexplored. The obligate marine fungus Paradendryphiella salina was isolated from several healthy brown macrophytes species. Novel α-hydroxy butenolides produced by P. salina were purified and characterized by NMR. These compounds interfere with the bacterial quorum sensing system as shown in bioassays with pathogenic bacterial model Pseudomonas aeruginosa. UHPLC-HRMS-based comparative metabolomics revealed the presence of the main α-hydroxy γ-butenolides among all the P. salina strains isolated from the different hosts as well as a high metabolic variability related to the alga-host species. Collectively, these findings highlight the key role of microbial chemical signaling that may occur within the algal holobiont.
Highlights
Marine macrophytes harbor a wide range of mutualistic microorganisms that contribute to their host health through their life cycle and are involved in maintaining the physiological status of their host (Wahl et al, 2012; Egan et al, 2013; Singh and Reddy, 2015)
To identify the features found in the metabolomics analysis, P. salina strain LD40H was cultivated at large scale, and its metabolites were purified and identified with standard natural product approaches
The heteronuclear multiple bond correlation (HMBC) spectrum pointed out correlations between the methyl singlet H-6 at δ 1.75 and the carbonyl C-5 at δC 172.4, the oxygenated tetrasubstituted carbon C-4 at δC 85.2, and the carbon C-3 at δC 131.2 ppm
Summary
Marine macrophytes harbor a wide range of mutualistic microorganisms that contribute to their host health through their life cycle and are involved in maintaining the physiological status of their host (Wahl et al, 2012; Egan et al, 2013; Singh and Reddy, 2015). QS requires the synthesis, exchange, and perception of bacterial signaling molecules, named autoinducers (AI) This mechanism has been described in eukaryotes, in fungi, where they regulate processes such as pathogenesis, sporulation, morphological differentiation, secondary metabolite production, and biofilm formation (Barriuso et al, 2018). Of note is that fungi in the environment are often competing with bacteria hinting at an inter-kingdom chemical signaling system and may produce inhibitors of bacterial QS (Deveau et al, 2018) This process is referred to as quorum quenching and can change the synthesis, release, accumulation, or recognition of the QS signals (Dong et al, 2001). Mass spectrometry (MS)based metabolomics highlighted the presence of α-hydroxyl γ-butenolides among the P. salina strains as well as a hostspecificity of P. salina metabolomes
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