Abstract
Diffusible signal factor (DSF) represents a family of widely conserved quorum sensing (QS) signals involved in the regulation of virulence factor production in many Gram-negative bacterial pathogens. Quorum quenching, which disrupts QS either by degradation of QS signals or interference of signal generation or perception, is a promising strategy for prevention and control of QS-mediated bacterial infections. In this study, a novel DSF-degrading strain, HN-2, was isolated from contaminated soil and identified as Cupriavidus sp. The isolate exhibited superior DSF degradation activity and completely degraded 2 mmol·L–1 of DSF within 24 h. Analysis of the degradation products of DSF by gas chromatography–mass spectrometry led to the identification of trans-2-decenoic acid methyl ester as the main intermediate product, suggesting that DSF could be degraded by oxidation and hydroxylation. Moreover, this study presents for the first time, evidence that Cupriavidus sp. can reduce the black rot disease caused by Xanthomonas campestris pv. campestris (Xcc). Application of the HN-2 strain as a biocontrol agent could substantially reduce the disease severity. These findings reveal the biochemical basis of a highly efficient DSF-degrading bacterial isolate and present a useful agent for controlling infectious diseases caused by DSF-dependent bacterial pathogens.
Highlights
Black rot pathogen Xanthomonas campestris pv. campestris (Xcc) has a wide host range but mainly infects cruciferous crops
Microorganisms 2020, 8, 45 significantly reduce the black rot disease severity caused by Xcc. These results suggest that the HN-2 strain possesses promising potential that can be further expanded for better control of Diffusible signal factor (DSF)-dependent pathogens and protection of plants from the respective infectious diseases
According to the results of the soil enrichment culture, four morphologically different bacterial bacterial strains were attained by the streaking plate method and named as HN-1, HN-2, HN-3, and strains were attained by the streaking plate method and named as HN-1, HN-2, HN-3, and HN-4, HN-4, respectively
Summary
Black rot pathogen Xanthomonas campestris pv. campestris (Xcc) has a wide host range but mainly infects cruciferous crops. Campestris (Xcc) has a wide host range but mainly infects cruciferous crops. Important cruciferous crops are consistently damaged by the black rot pathogen, and the death of plant tissues by Xcc infection leads to severe crop losses [1,2]. The Xcc inoculum spreads from the infected seed to the epicotyl of healthy seeds, and as a result, cotyledons develop blackened margins and shrivel and drop [1,4]. Bacteria in guttation droplets are spread to neighboring plants by wind, rain, water splashes, and Microorganisms 2020, 8, 45; doi:10.3390/microorganisms8010045 www.mdpi.com/journal/microorganisms of the soft rot potato pathogens Pectobacteria atrosepticum and Pectobacteria carotovorum [15,17,18,19].
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