Identification and characterization of N-acylhomoserine lactone-acylase from the fish intestinal Shewanella sp. strain MIB015.

N-Acylhomoserine lactones (AHLs) are used as quorum-sensing signal molecules by many gram-negative bacteria. We have reported that Shewanella sp. strain MIB015 degrades AHLs. In the present study, we cloned the aac gene from MIB015 by PCR with specific primers based on the aac gene in Shewanella oneidensis strain MR-1, which showed high homology with the known AHL-acylases. Escherichia coli expressing Aac showed high degrading activity of AHLs with long acyl chains. HPLC analysis revealed that Aac worked as AHL-acylase, which hydrolyzed the amide bond of AHL. In addition, expression of Aac in fish pathogen Vibrio anguillarum markedly reduced AHL production and biofilm formation. In conclusion, this study indicates that Aac might be effective in quenching quorum sensing of fish pathogens.