Quorum quenching is an antivirulence strategy employed by endophytic bacteria
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Bacteria predominantly use quorum sensing to regulate a plethora of physiological activities such as cell-cell crosstalk, mutualism, virulence, competence, biofilm formation, and antibiotic resistance. In this study, we investigated how certain potent endophytic bacteria harbored in Cannabis sativa L. plants use quorum quenching as an antivirulence strategy to disrupt the cell-to-cell quorum sensing signals in the biosensor strain, Chromobacterium violaceum. We used a combination of high-performance liquid chromatography high-resolution mass spectrometry (HPLC-ESI-HRMSn) and matrix-assisted laser desorption ionization imaging high-resolution mass spectrometry (MALDI-imaging-HRMS) to first quantify and visualize the spatial distribution of the quorum sensing molecules in the biosensor strain, C. violaceum. We then showed, both quantitatively and visually in high spatial resolution, how selected endophytic bacteria of C. sativa can selectively and differentially quench the quorum sensing molecules of C. violaceum. This study provides fundamental insights into the antivirulence strategies used by endophytes in order to survive in their ecological niches. Such defense mechanisms are evolved in order to thwart the plethora of pathogens invading associated host plants in a manner that prevents the pathogens from developing resistance against the plant/endophyte bioactive secondary metabolites. This work also provides evidence towards utilizing endophytes as tools for biological control of bacterial phytopathogens. In continuation, such insights would even afford new concepts and strategies in the future for combating drug resistant bacteria by quorum-inhibiting clinical therapies.
KeywordsBacterial endophytes Quorum quenching N-acylated homoserine lactones Cannabis sativa L High-resolution mass spectrometry MALDI imaging high-resolution mass spectrometry Microbe-microbe interaction Microbe-plant interaction Phytopathology
This research was funded by the Ministry of Innovation, Science and Research of the German Federal State North Rhine-Westphalia (NRW) and TU Dortmund by a scholarship to P.K. from the CLIB-Graduate Cluster Industrial Biotechnology. We thank the German Research Foundation (DFG) for financing the MALDI imaging high-resolution mass spectrometers. We are thankful to Federal Institute for Drugs and Medical Devices (Bundesinstituts für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany for granting us the necessary permissions for working with Cannabis plants (BtM number 458 49 89). S.K. was a Visiting Researcher at the Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 15 3RB, UK, during part of the work and preparation of the manuscript (Apr 2013 to Mar 2014). S.K. gratefully acknowledges M.S. for approving and authorizing, Dr. Gail M. Preston for hosting, and TU Dortmund for supporting his stay at the University of Oxford.
Conflict of Interest
The authors declare no conflict of interest.
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