Biotechnology Bulletin ›› 2023, Vol. 39 ›› Issue (9): 255-267.doi: 10.13560/j.cnki.biotech.bull.1985.2023-0086

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Properties of Bacillus subtilis Strain BBs-27 Fermentation Broth and the Inhibition of Lipopeptides Against Fusarium culmorum

MIAO Yong-mei1(), MIAO Cui-ping2, YU Qing-cai1   

  1. 1. College of Life and Health Science, Anhui Science and Technology University, Fengyang 233100
    2. School of Life Sciences, Yunnan University, Kunming 650504
  • Received:2023-02-07 Online:2023-09-26 Published:2023-10-24

Abstract:

Bacillus subtilis strain BBs-27 isolated from the medicinal plant Bulbophyllum sp. shows strong antifungal activity against Fusarium culmorum. In order to further understand the composition of fermentation broth and its antifungal mechanism, the properties of fermentation broth were studied by acid-base treatment, ultraviolet irradiation and enzymolysis. On the above basis, the type of lipopeptides(LPs)in the fermentation broth was identified using LC-MS. The antifungal effects of LPs were analyzed from the morphology, physiology and transcriptome levels. The results showed that the antifungal activity of the fermentation broth was the strongest at pH=6, and decreased significantly at pH < 4 or > 10, and declined significantly when UV irradiation in over 10 min, easily hydrolyzed by other three proteases, but insensitive to pepsin. It was speculated that antifugal antifugal substances were mainly lipopeptides, and contained a small amount of protein. LPs LPs were mainly iturin and fengycin by LC-MS analysis. The fungus mycelium treated by LPs was twisted, informed and abnormally swollen under SEM. LPs had a significant impact on the activities of SOD, POD, CAT and the contents of soluble protein and soluble sugar, and all five physiological indicators were highly correlated with antifungal rate. With F. graminis genome as reference, Q20 and Q30 were above 96%, 91% respectively, GC content ranged from 52.27% to 52.87%, comparison rate was above 78%. Total 712 differentially expressed genes(DEGs)were screened, of which 393 were up-regulated and 319 were down-regulated. The Go functional annotation classification showed that 712 DEGs were mainly involved in 6 biological processes, 11 cell components and 12 molecular functions. KEGG enrichment analysis revealed that the DEGs were mainly enriched in the metabolisms of carbohydrate, lipid, amino acid, cofactors and vitamins. Genes including GAO, CHS3, MPG1, FGSG_02016, IPDH and ODC responding to LPs affected the fungus growth by interfering with the normal synthesis of cell wall, cell membrane, amino acids and antioxidant enzymes. These results provide a theoretical basis for further development and utilization of safe microbial pesticides.

Key words: lipopeptides, Bacillus, Fusarium culmorum, scanning electron microscope, mycelium morphology, transcriptome, fermentation property, antifungal rate