Abstract
Many Gram-negative plant pathogenic bacteria employ a N-acylhomoserine lactone (AHL)-based quorum sensing (QS) system to regulate their virulence traits. A sustainable biocontrol strategy has been developed using quorum quenching (QQ) bacteria to interfere with QS and protect plants from pathogens. Here, the prevalence and the diversity of QQ strains inhabiting tobacco leaf surfaces were explored. A total of 1177 leaf-associated isolates were screened for their ability to disrupt AHL-mediated QS, using the biosensor Chromobacterium violaceum CV026. One hundred and sixty-eight strains (14%) are capable of interfering with AHL activity. Among these, 106 strains (63%) of the culturable quenchers can enzymatically degrade AHL molecules, while the remaining strains might use other QS inhibitors to interrupt the chemical communication. Moreover, almost 79% of the QQ strains capable of inactivating AHLs enzymatically have lactonase activity. Further phylogenetic analysis based on 16S rDNA revealed that the leaf-associated QQ bacteria can be classified as Bacillus sp., Acinetobacter sp., Lysinibacillus sp., Serratia sp., Pseudomonas sp., and Myroides sp. The naturally occurring diversity of bacterial quenchers might provide opportunities to use them as effective biocontrol reagents for suppressing plant pathogen in situ.
Highlights
The form of microbial chemical communication known as quorum sensing (QS) occurs via specific diffusible signal molecules [1]
To analyze the QS-quenching potential of the isolated bacteria originating from the tobacco phyllosphere, a degradation assay was performed with Chromobacterium violaceum CV026 sensor strains
The initial screening of the isolates revealed that the acylhomoserine lactone (AHL)-quenchers represented 14% of the culturable leaf-associated bacteria (Figure 2)
Summary
The form of microbial chemical communication known as quorum sensing (QS) occurs via specific diffusible signal molecules [1]. Many Gram-negative plant-associated bacteria pathogens have been reported to regulate their virulence by AHL-based QS [4]. Phyllosphere, an important habitat for microorganisms, should deserve research attention as a resource of quenching bacteria [14] They have the ability to reside within the same ecological niche as their pathogenic counterparts, which would protect plant effectively [15]. A systematic understanding of leaf-dwelling QQ bacteria should help to highlight the importance of the interactions within phyllosphere bacteria communities This knowledge will broaden biotechnological research in the field of the biocontrol of plant diseases, based on AHL-degrading phyllosphere bacterial resources. An in-depth analysis, based on the 16S rRNA gene, was performed to gain insight into the phylogenetic profiles of AHL-degrading phyllosphere bacteria
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