Isolation of the bacteria with quorum quenching activity against Pectobacterium carotovorum subsp. carotovorum

One hundred seventhy seven quorum quenching bacteria were isolated from Solanaceae family using two methods of minimal medium containing synthetic acyl homoserine lactone signal 3-oxo-C6-HSL and sole common culture medium. Eleven isolates of bacteria, includingPseudomonas, Enterobacter, Acinetobacter and Bacillus were identified as bacteria with high quorum quenching ability, especially the genus Pseudomonas showed the highest quorum quenching activity. Investigating quorum quenching mechanisms among these bacteria revealed that enzymes and non-enzymatic small compounds with quorum quenching activity were involved in this process. However, most of the bacteria showing enzymatic activity were confirmed by HPLC. Results also showed that one isolate of Acinetobacter calcoaceticus obtained by the second method, had non-enzymatic quorum quenching activity. The quorum quenching bacteria mainly reduced the biofilm and pathogenicity of Pectobacterium carotovorum subsp. carotovorum on potato and cactus. Therefore, there was a direct relationship between increasing quorum quenching activity and biocontrol ability against thispathogen. However, there were some exceptions. In addition, some isolates of Pseudomonas as the best biocontrol agents were identified, which were effective against the pathogen based on quorum quenching.