The aim of the present study was to isolate a variety of quorum quenching bacteria (QB) from the rhizosphere and phyllosphere of three agricultural plants using minimal medium (MM)- and nonminimal medium (NM)-based methods. The members of the Pseudomonas genus constituted the most abundant QB genus, particularly in the rhizospheres of all plant samples and showed the highest quorum quenching (QQ) activity according to a screening assay using a biosensor and 3-oxo-C6-HSL (as an important quorum sensing signal in many phytopathogenic bacteria). In addition, QQ-Pseudomonas were recognised as versatile biocontrol agents against non-bacterial and bacterial plant pathogens, such as Pectobacterium carotovorum subsp. carotovorum (Pcc). Three types of quenching activities, including intracellular and extracellular enzymatic and non-enzymatic activities, were observed in QQPseudomonas. Pseudomonas strains, particularly NM-isolated strains with extracellular activity, are the strongest QQ-based biocontrol agents.

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