Abstract
Quorum sensing (QS) is a cell density-dependent mechanism that regulates the expression of specific genes in microbial cells. Quorum quenching (QQ) is a promising strategy for attenuating pathogenicity by interfering with the QS system of pathogens. N-Acyl-homoserine lactones (AHLs) act as signaling molecules in many Gram-negative bacterial pathogens and have received wide attention. In this study, a novel, efficient AHL-degrading bacterium, Acinetobacter sp. strain XN-10, was isolated from agricultural contaminated soil and evaluated for its degradation efficiency and potential use against QS-mediated pathogens. Strain XN-10 could effectively degrade N-(3-oxohexanoyl)-L-homoserine lactone (OHHL), N-hexanoyl-L-homoserine lactone (C6HSL), N-(3-oxododecanoyl)-L-homoserine lactone (3OC12HSL), and N-(3-oxooctanoyl)-L-homoserine lactone (3OC8HSL), which all belong to the AHL family. Analysis of AHL metabolic products by gas chromatography–mass spectrometry (GC-MS) led to the identification of N-cyclohexyl-propanamide, and pentanoic acid, 4-methyl, methyl ester as the main intermediate metabolites, revealing that AHL could be degraded by hydrolysis and dehydroxylation. All intermediates were transitory and faded away without any non-cleavable metabolites at the end of the experiment. Furthermore, strain XN-10 significantly attenuated the pathogenicity of Pectobacterium carotovorum subsp. carotovorum (Pcc) to suppress tissue maceration in carrots, potatoes, and Chinese cabbage. Taken together, our results shed light on the QQ mechanism of a novel AHL-degrading bacterial isolate, and they provide useful information which show potential for biocontrol of infectious diseases caused by AHL-dependent bacterial pathogens.
Highlights
Pectobacterium carotovorum subsp. carotovorum (Pcc), formerly known as Erwinia carotovora subsp. carotovora, is a pathogen with a broad host range
Several Acyl-homoserine lactones (AHLs)-degrading strains were isolated from soil samples, and the one possessing the highest degradation efficacy was designated as XN-10
This study proved that Acinetobacter sp. can reduce the severity of soft rot disease caused by Pcc by degrading the quorum sensing (QS) signals
Summary
Pectobacterium carotovorum subsp. carotovorum (Pcc), formerly known as Erwinia carotovora subsp. carotovora, is a pathogen with a broad host range. Carotovora, is a pathogen with a broad host range. Carotovorum (Pcc), formerly known as Erwinia carotovora subsp. It causes soft rot disease in a variety of cruciferous crops during cultivation, post-harvest processing, and storage [1]. Soft rot is an epidemic, worldwide, and severe disease in many valuable commercial vegetables, such as potatoes (Solanum tuberosum), Chinese cabbage (Brassica pekinensis), carrots (Daucus carota), etc., causing significant economic losses [2,3,4]. To reduce the effects of soft rot, some plant extracts have been developed to inhibit the pathogenic strain Pcc [5]. Many chemicals have been used to control or kill pathogenic bacteria, such as copper sulphate, sodium hypochlorite, and antibiotics [6]. Quorum quenching (QQ) based on the disruption of quorum sensing (QS) has been put forward and regarded as a promising strategy to combat pathogenic infection [9]
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