Study On Marine Flavobacterium Against Phytopathogens And Antifungal Activity Compouds

To control crop pathogenic fungus,it is exigent of screening new natural antifungal compounds.But along with research unceasingly thorough,the probability of obtaining new antifungal compounds from terrestrial microorganism has reduced gradually.Under this situation,for the first time,in this paper,we studied on marine Flavobacterium sp. strain WWP37 against phytopathogens and broad spectrum antifungal activity compounds.The antifungal compounds were purified and identified.Its fermentation conditions for producing the antifungal compounds were studied.Suppression effect of strain WWP37 on SRS was also determined.The results were followed as:1.In our study,three plant pathogenic Fusariurn oxysporum,Biotrytis cinerea and Sclerotinia sclerotiorum were used as indicating strains.And 176 marine isolates were used to screen antifungal substance-producing bacteria.The results showed that 11 marine strains which had high antifungal effective were picked up.Finally,strain WWP37(MCCC 1A01368) was confirmed of this activity.2.The active compounds could maintain most antifungal activities when heated at 100℃for 20 min,or treated with UV radiation for 90 min.Furthermore,antifungal compounds remained strong activity over a wide pH range from 4.0 to 10.0.The active compounds could be extracted with n-butanol.TLC-bioautography results showed that the strain WWP37 produced at least two active compounds.Compared with the paper chromatograms of eight-solvent system from different standards,the antifungal compound was similar as aureothricin and thiolutin.3.Compound BF-1 was purified by means of gel filtration chromatography,solid phase extraction and HPLC.Then BF-1 was analysed by UV absorption spectrum and LC/MS.The ultraviolet characteristic absorptions of BF-1 were similar as characteristic absorptions of aureothricin.Its molecular weight was 699 Da after systematic analysis of the fragmentation peaks appearing in the mass spectrum.With the same parent ring as aureothricin,the results suggested that BF-1 was a member of the aureothricin family.4.It was proved through orthogonal experiments that the optimum medium for producing the antifungal compounds was 0.6%cane sugar,1.2%yeast extract powder, 1.4%NaCl and 0.80%MgSO₄;the optimum culturing conditions were inoculated with 8 hours' seedage and 7.0%of inocula,and cultured for 24 hours at pH 8.0.Effect of culture supernatant of strain WWP37 against SRS was measured in greenhouse and the result showed that 76.7%of the plants were still healthy after 21 d with the sterilized supernatant treatment.From scanning electron micrograph of WWP37,antifungal effects revealed that the cells of the hypha of Fusarium oxysporum began to shorten,the cell walls were broken and the protoplasm leaked out after treatment with fermentation of WWP37.Preliminary analysis on antibiotic properties showed BF-1 was a novel pyrrole-antibiotic and had a significant antifungal activity on Sclerotinia sclerotiorum. This is the first report on the antifungal activity of a novel pyrrole-antibiotic from marine Flavobacterium and it may be a promising agricultural antibiotics.