A NOVEL AHLDEGRADING RHIZOBACTERIUM QUENCHES THE VIRULENCE OF PECTOBACTERIUM ATROSEPTICUM ON POTATO PLANT
E. Mahmoudi, A. Ahmadi, B.E. Sayed-Tabatabaei, C. Ghobadi, A. Akhavan, N. Hasanzadeh, V. Venturi
Quorum sensing (QS) is a regulatory mechanism that connects gene expression to cell density in bacteria. The expression of numerous genes including those involved in the production of virulence determinants in Pectobacterium atrosepticum are regulated in this way. The signal molecules involved in QS in P. atroseptium belong to the group of N-acyl homoserine lactones (AHLs). Recently, several soil bacteria were found to degrade AHLs, thereby interfering with the QS system. In this research, twelve strains of AHL-degrading rhizobacteria were isolated from potato rhizosphere. According to ribotyping analysis, these isolates fell into four groups belonging to the genera Bacillus, Arthrobacter, Pseudomonas and Chryseobacterium. All these isolates were capable to degrade both synthetic and natural AHLs produced by P. atrosepticum strain SM1. In this report, Chryseobacterium sp. was isolated as an AHL-degrading bacterium for the first time and shown that it could interfere with QSdependent bacterial infection of P. atrosepticum SM1. Chryseobacterium sp. and several other tested isolates effectively inhibited maceration of potato tuber tissue by P. atrosepticum. The attenuation of the pathogenicity might be due to the quenching of QS-regulated production of extracellular enzymes by P. atroseptium SM1. Chryseobacterium sp. isolated in this study might be a useful agent in the biocontrol of bacterial plant diseases.