Study On The Biocontrol Mechanism Against Banana Vasicular Wilt And The Antimicrobial Substance Of Bacillus Subtilis CS16

In order to probe into the biocontrol mechanism of Bacillus subtilis strain CS16(Bacillus subtilis subsp.subtilis),discover new activities and develop effective biocontrol agents, the biocontrol mechanism against Banana vasicular wilt of Bacillus subtilis CS16 was analyzed, and its extracellular metabolites were isolated and purified with qualitative and quantitative analysis, while the encoding genes related to its activities were cloned and detected. The main research contents and results are as follows:1. In order to realize the biocontrol potential of strain CS16, its antimicrobial activity was detected. The results showed that strain CS16 had strong inhibition against many pathogenic fungi with clear inhibition zone but rather weak in anti-bacterial activities, so the strain CS16 has high specifici inhibition against pathogenic fungi, which can be further developed into biocontrol agents to control plant fungal diseases.2. The biocontrol mechanism against Fusarium oxysporum f.sp.cubense of Bacillus subtilis strain CS16 was discussed. The results showed that the biocontrol mechanism of strain CS16 mainly included competition, antagonistic effect and the induction of plant disease resistance effect.3. The extracellular metabolites of strain CS16 were isolated and purified with qualitative and quantitative analysis. The results showed that the crude extract of the fermented liquid from strain CS16 had distinct inhibition against Fusarium oxysporum f.sp.cubense and its minimal inhibitory concentration (MIC) was 0.0625mg/mL.And then the extract was purified by reverse-phase silica gel column, sephadex LH-20 gel column and normal-phase silica gel column. The antimicrobial substance in the purified extract was cyclic lipopeptide by thin-layer chromatography analysis.4. The encoding genes related to its activities were cloned and detected with the genome DNA of strain CS16 as template. The results showed that the strain CS16 contained fenD gene encoding Fengycin, two functional genes (ituD and lpa-14) encoding iturin A. The antimicrobial substance of strain CS16 were cyclic lipopeptide, which were possibly Fengycin and/or iturin A.