A probable aculeacin A acylase from the Ralstonia solanacearum GMI1000 is N-acyl-homoserine lactone acylase with quorum-quenching activityReport as inadecuate

A probable aculeacin A acylase from the Ralstonia solanacearum GMI1000 is N-acyl-homoserine lactone acylase with quorum-quenching activity - Download this document for free, or read online. Document in PDF available to download.

BMC Microbiology

, 9:89

First Online: 09 May 2009Received: 22 July 2008Accepted: 09 May 2009


BackgroundThe infection and virulence functions of diverse plant and animal pathogens that possess quorum sensing systems are regulated by N-acylhomoserine lactones AHLs acting as signal molecules. AHL-acylase is a quorum quenching enzyme and degrades AHLs by removing the fatty acid side chain from the homoserine lactone ring of AHLs. This blocks AHL accumulation and pathogenic phenotypes in quorum sensing bacteria.

ResultsAn aac gene of undemonstrated function from Ralstonia solanacearum GMI1000 was cloned, expressed in Escherichia coli; it inactivated four AHLs that were tested. The sequence of the 795 amino acid polypeptide was considerably similar to the AHL-acylase from Ralstonia sp. XJ12B with 83% identity match and shared 39% identity with an aculeacin A acylase precursor from the gram-positive actinomycete Actinoplanes utahensis. Aculeacin A is a neutral lipopeptide antibiotic and an antifungal drug. An electrospray ionisation mass spectrometry ESI-MS analysis verified that Aac hydrolysed the amide bond of AHL, releasing homoserine lactone and the corresponding fatty acids. However, ESI-MS analysis demonstrated that the Aac could not catalyze the hydrolysis of the palmitoyl moiety of the aculeacin A. Moreover, the results of MIC test of aculeacin A suggest that Aac could not deacylate aculeacin A. The specificity of Aac for AHLs showed a greater preference for long acyl chains than for short acyl chains. Heterologous expression of the aac gene in Chromobacterium violaceum CV026 effectively inhibited violacein and chitinase activity, both of which were regulated by the quorum-sensing mechanism. These results indicated that Aac could control AHL-dependent pathogenicity.

ConclusionThis is the first study to find an AHL-acylase in a phytopathogen. Our data provide direct evidence that the functioning of the aac gene NP520668 of R. solanacearum GMI1000 is via AHL-acylase and not via aculeacin A acylase. Since Aac is a therapeutic potential quorum-quenching agent, its further biotechnological applications in agriculture, clinical and bio-industrial fields should be evaluated in the near future.

AbbreviationsAHLsN-acylhomoserine lactones

C4-HSLN-butanoyl-L-homoserine lactone


C7-HSLN-heptanoyl-L-homoserine lactone

C8-HSLN-octanoyl-L-homoserine lactone

C10-HSLN-decanoyl-L-homoserine lactone

C12-HSLN-dodecanoyl-L-homoserine lactone

C14-HSLN-tetradecanoyl-L-homoserine lactone

3OC12-HSLN-3-oxo-dodecanoyl -homoserine lactone

HSL-OPAHomoserine lactone-o-phthaldialdehyde

HPLCHigh-performance liquid chromatography.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2180-9-89 contains supplementary material, which is available to authorized users.

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Author: Chin-Nung Chen - Chii-Jaan Chen - Chen-Ting Liao - Chia-Yin Lee

Source: https://link.springer.com/article/10.1186/1471-2180-9-89

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