Aims: To screen novel micro-organisms and enzymes capable of degrading 3-hydroxypalmitic acid methyl ester (3-OH PAME), the quorum-sensing signal molecule (quormone), which regulates the virulence of Ralstonia solanacearum. Methods and Results: Ideonella sp. 0-0013, a betaproteobacterium isolated from soil using the selective-enrichment culture method, was grown on plates containing 3-OH PAME as its main carbon source. beta-Hydroxypalmitate methyl ester hydrolase (beta HPMEH) purified from the supernatant of the Ideonella sp. 0-0013 culture exhibited high hydrolysing activity towards the ester bond of 3-OH PAME and eliminated the 3-OH PAME activity, thereby reducing the virulence of R. solanacearum. An Escherichia coli transformant of the beta hpmeh gene expression vector degraded 3-OH PAME, and the crude enzyme from the transformant inhibited in vitro production of the R. solanacearum exopolysaccharide (EPS). Conclusions: The ability of bHPMEH to hydrolyse 3-OH PAME inhibited the production of EPS by the R. solanacearum wild-type strain, indicating that bHPMEH inhibits the effects of activation of virulence genes. This ability will be potentially useful for pest control of the wilt disease caused by this bacterium. Significance and Impact of the Study: This enzyme is the first protein that has been found to degrade a quormone other than N-acyl homoserine lactone.