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Abstract: An N-acyl homoserine lactonase gene aiiA, transcribed by a strong and constitutive Escherichia coli promoter P lpp (Accession No. EU723847), was transformed into Lysobacter enzymogenes strain OH11, creating strain OH11A. The N-acyl-homoserine lactone (AHL)-degradation assay showed that transformant OH11A acquired the ability to degrade AHL molecules produced by Agrobacterium tumefaciens, Pectobacterium carotovorum, Pseudomonas syringae pv. tomato strain DC3000 and Acidovorax avenae subsp. citrulli. Pathogenicity tests showed that while the parental strain OH11 did not reduce P. carotovorum infection, the transformant OH11A caused a strong reduction of Pectobacterium virulence on Chinese cabbage and cactus, whereas strain OH11A did not seem to interfere with the normal growth of this pathogen in cabbages. In antimicrobial activity assays, strain OH11A and OH11 showed similar antimicrobial activity against Phytophthora capsici and Sclerotinia sclerotiorum. This work provided a new strategy for developing genetically engineered multi-functional L. enzymogenes strains that possessed the ability to biologically control fungal pathogens and reduce bacterial pathogenicity. [Copyright &y& Elsevier]