Simple unicellular organisms such as bacteria have a INTRODUCTION remarkable ability for social cooperation. In a competitive

Abstract

A total of 45 bacterial isolates were obtained from rhizosphere soil of rice and tomato in Peninsular Malaysia, of which 6 have the ability to degrade quorum sensing signal molecules, N-acyl-homoserine lactones (AHLs), in vitro. The six isolates designated as SP17, SPB2, SPB9, CHB4, CHB18 and CHB19 were identified as Bacillus thuringiensis, Bacillus sp., Bacillus amyloliquefaciens, Bacillus cereus, Bacillus megaterium and Bacillus pumilus, respectively, using 16S ribosomal RNA sequence-based identification. PCR amplification of AHL lactonase genes (aiiA) using aiiA primers revealed the presence of aiiA gene homologues in all of the isolates which may contribute to its AHL degradation ability. These AHL degrading bacteria have the potential for use as biological control agents against the papaya dieback disease pathogen, Erwinia mallotivora, in Malaysia, where their virulence and pathogenicity are regulated by AHL- mediated quorum sensing.