Structural and Functional Insights into Iturin W, a Novel Lipopeptide Produced by the Deep-Sea Bacterium Bacillus sp. Strain wsm-1

摘要

In the present study, a deep-sea bacterial strain designated Bacillus sp. strain wsm-1 was screened and found to exhibit strong antifungal activity against many plant-pathogenic fungi, and corresponding antifungal agents were thereby purified and determined by tandem mass spectrometry to be two cyclic lipopeptide homologs. These homologs, which were different from any previously reported lipopeptides, were identified to possess identical amino acid sequences of beta-amino fatty acid-Asn-Ser-Asn-Pro-Tyr-Asn-Gln and deduced as two novel lipopeptides designated C-14 iturin W and C-15 iturin W. Electron microscopy observation indicated that both iturin W homologs caused obvious morphological changes and serious disruption of plasma membrane toward fungal cells, while C-15 iturin W exhibited more serious cell damages than C-14 iturin W did, which was well consistent with the results of the antifungal activity assays. To improve the yield and antifungal activity of iturin W, the effects of different carbon and nitrogen sources and amino acids on production of C-14 iturin W and C-15 iturin W were investigated. The results indicated that supplements of most of the detected carbon and nitrogen sources could increase the yield of C-14 iturin W, but inhibit the yield of C-15 iturin W, while supplements of tryptone and most of the detected amino acids could increase the yield of both C-14 iturin W and C-15 iturin W.