The spent culture supernatant of Pseudomonas syringae contains azelaic acid

Danilo Licastro,Luciano Navarini,Valentina Lonzarich,Paola Cescutti,Roberto Rizzo,Corrado Guarnaccia,Sree Gowrinadh Javvadi,Vittorio Venturi

doi:10.1186/s12866-018-1352-z

Abstract

BackgroundPseudomonas syringae pv. actinidiae (PSA) is an emerging kiwifruit bacterial pathogen which since 2008 has caused considerable losses. No quorum sensing (QS) signaling molecule has yet been reported from PSA and the aim of this study was to identify possible intercellular signals produced by PSA.ResultsA secreted metabolome analysis resulted in the identification of 83 putative compounds, one of them was the nine carbon saturated dicarboxylic acid called azelaic acid. Azelaic acid, which is a nine-carbon (C9) saturated dicarboxylic acid, has been reported in plants as a mobile signal that primes systemic defenses. In addition, its structure,(which is associated with fatty acid biosynthesis) is similar to other known bacterial QS signals like the Diffusible Signal Facor (DSF). For these reason it could be acting as s signal molecule. Analytical and structural studies by NMR spectroscopy confirmed that in PSA spent supernatants azelaic acid was present. Quantification studies further revealed that 20 μg/L of were present and was also found in the spent supernatants of several other P. syringae pathovars. The RNAseq transcriptome study however did not determine whether azelaic acid could behave as a QS molecule.ConclusionsThis study reports of the possible natural biosynthesis of azelaic acid by bacteria. The production of azelaic acid by P. syringae pathovars can be associated with plant-bacteria signaling.

Highlights

Pseudomonas syringae pv. actinidiae (PSA) is an emerging kiwifruit bacterial pathogen which since 2008 has caused considerable losses
We report the possible biosynthesis of azelaic acid by P. syringae pathovars and possible biological roles are discussed
Metabolome studies of P. syringae pv. actinidiae and P. savastanoi pv. savastanoi With the aim of identifying novel signaling molecules produced by P. syringae pv. actinidiae (PSA), we analyzed the extracellular metabolome profile using gas chromatography coupled with mass spectrometry (GCMS)

Summary

Introduction

Pseudomonas syringae pv. actinidiae (PSA) is an emerging kiwifruit bacterial pathogen which since 2008 has caused considerable losses. In the last 20 years, many bacterial species have been reported to produce QS signals and it is reasonable to assume that most, if not all, use small chemical compounds to communicate with their neighborhood [5,6,7]. In the Pseudomonas group of phytopathogens, QS is a common regulatory mechanism. It occurs commonly via the LuxI/LuxR circuit, which produces and responds to N-acylhomoserine lactone (AHL) signals. LuxI-family proteins are the signal synthases that are responsible for producing AHLs, whereas LuxR-family members are the AHL-responsive cytoplasmic DNA-binding transcriptional activators. Several Gram-negative bacteria produce long chain fatty acids and fatty acid methyl esters as QS signal molecules. Some examples of these types of molecules are (i) PQS (pseudomonas quinolone signal) 2-heptyl-3-hydroxy-4(1H)-quinolone is produced by Pseudomonas aeruginosa, (ii) HHQ signal, 2-heptyl-4 (1H)-quinolone by Bacillus atrophaeus and Pseudomonas [11, 12] (iii) the DSF, diffusible signaling factor, cis-11-methyl-2-dodecenoic acid by Xanthomonas and Burkholderia [13,14,15]

Objectives

Methods

Results

Discussion

Conclusion