Abstract | Quorum sensing (QS) molecules are involved in the regulation of complicated processes helping bacterial population benefit from their cell-density. The co-evolution of prokaryotes and eukaryotes raises the prospect of the existence of inter-kingdom signalling pathways, promoting parasitic/symbiotic relationships. While the members of each kingdom possess hormone-like molecules for cell–cell communication, the members of any given kingdom also respond to the signals produced by another. So, QS plays a major role in this cross-talk. Bacterial antagonistic activity against fungi is considered as an inter-kingdom communication. Interestingly, several bacteria like Bacillus, Lactobacillus and Pseudomonas have shown in laboratory experiments the ability to inhibit fungal growth and production of aflatoxins by Aspergillus. During the screening of antagonistic bacteria against Aspergillus flavus (causes pre-/post-harvest diseases in seed-crops) in vitro, Bacillus subtilis was identified having high antifungal activity. Bacillus licheniformis has industrial application due to its production of antimicrobial compounds. B. licheniformis is related to B. subtilis genetically, whose control of competence-sporulation is regulated by a QS mechanism (comQXPA operon). QS process in B. subtilis are regulated by a specific molecule, ComX pheromone. Pheromone encoding genes have been identified in B. licheniformis NCIMB-8874. To further investigate cell-cell communication, we designed a primer pair to amplify the QSM encoding genes. The comQX locus was sub-cloned into a shuttle vector under the control of an inducible promoter. The shuttle vector was expressed in E. coli and pheromone was isolated by reverse phase chromatography. Pheromone as a QSM is potential signal for communicating between kingdoms and could be applied for biocontrol purposes. Identification of new antifungal peptides against A. flavus could lead to the development of biotechnological strategies which facilitate control of aflatoxin contamination and genetic engineering of plant resistance to fungi through the exploitation of genes related to the bacterial antifungal peptide molecules. |
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