Screening and identification of a Streptomyces strain with quorum sensing inhibitory activity and effect of the crude extracts on virulence factors of Erwinia amylovora

【Objective】 To explore the potential metabolisms for natural product compounds from actinomycetes in the arid area and investigate effect of the quorum sensing inhibition on virulence factors in Erwinia amylovora. 【Methods】 Chromobacterium violaceum 026 (CV026) was used for the screening model of the quorum sensing inhibitions, the fermentation of actinomycetes isolated from soils in arid areas around the Kumutag Desert was carried out, and the quorum sensing inhibitory activity of the fermentation broth was tested using the Oxford Cup method. The strain was identified by the 16S rRNA gene sequence analysis, and effect of crude extracts from the broth on virulence factors of Erwinia amylovora was measured. In addition to that, liquid chromatography and mass spectrometry (LC-MS) was used to measure metabolites, and compounds with similar structure to reported quorum sensing inhibitors were selected to validate. 【Results】 Isolate K-9 was screened and identified to belong to the genus Streptomyces, which showed strong quorum sensing inhibitory activity and shared the highest similarities with Streptomyces rubradiris NBRC 14000^T(99.72%). The crude extracts of the broth effectively reduced the violacein production of CV026 and the swimming ability of Erwinia amylovora. Virulence factors of Erwinia amylovora such as biofilm, pyocyanin and rhamnolipid were inhabited significantly with the concentration-dependent interactions. A total of 635 compounds were identified from the crude extract by LC-MS, and 5 compounds with significant quorum sensing inhibitory activity were observed. 【Conclusion】 Streptomyces sp. K-9 is one potential new species isolated from arid areas, whose fermentation metabolites shows obvious quorum sensing inhibitory activity, and can inhibit virulence factors produced by Pseudomonas aeruginosa. Additionally, many kinds of novel quorum sensing inhibitors were obtained.