HARNESSING THE POTENTIAL OF QUORUM QUENCHING BACTERIA FOR THE CONTROL OF MULTIDRUG RESISTANT PHYTOPATHOGENIC BACTERIA
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Date
2022-12-31
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University of Agricultural Sciences, Bangalore
Abstract
Pathogenicity of bacteria by biofilm formation, antibiotic resistance and motility, and virulence factors production is regulated by a population density dependant phenomenon called quorum sensing(QS), a cell-to-cell communication ediated by autoinducer(AI) molecules. Destruction or inhibition of these AIs ceases the communication required for establishing the pathogenicity in plants called quorum quenching(QQ). Exploitation of QQ bacteria offers the most viable biocontrol strategy for the multidrug resistant phytopathogenic bacteria as these bacteria interfere with QS of phytopathogens only by degrading AIs and control virulence without hampering their growth. Preliminary screening of thirty-nine bacterial isolates obtained from eight different environmental samples by enrichment culture technique with C6HSL as QS molecule, using Chromobacterium violaceum MCC 4212 as a bioindicator yielded 14 isolates capable of inhibiting violacein production efficiently, a QS-mediated trait. Five of 14 isolates (HSL-13, HSL-31, HSL-32, HSL-61 and HSL-64) exhibited their QQ property without antagonism, a feature of an ideal QQ bacterium. In vitro maceration
attenuation by five isolates in potato, radish and cucumber proved their biocontrol efficiency against soft rot pathogen, Pectobacterium carotovorum subsp. carotovorum(Pcc), a multidrug resistant bacterium. Attenuation of QS-mediated virulence factors of Pcc viz., plant cell wall degrading enzymes and biofilm formation by the bacterial isolates confirmed the QQ-based biocontrol efficiency of these QQ isolates with AHL degradation efficiency of >90% and are extracellular.
In planta host range studies yielded three efficient isolates HSL-13, HSL-32 and HSL-64 that performed better in all five hosts. These quorum quenchers outperformed reference bacteria in their biocontrol as well as plant growth promoting potential in radish under pot culture conditions. Pseudomonas taiwanensis harbouring aiiA gene was identified in present study is responsible for AHL lactonase, quenches QS signals responsible for virulence by Pcc efficiently as predicted by molecular docking studies and rendered better biocontrol efficiency than others against the multidrug resistant Pcc.