脂肽类抗生素fengycin对大丽轮枝菌孢子萌发和微菌核形成的影响

枯草芽胞杆菌NCD-2菌株能够产生脂肽类抗生素fengycin和surfactin。本研究分别比较了NCD-2野生型菌株、丧失fengycin合成的突变子MF和丧失surfactin合成的突变子MS对大丽轮枝菌的抑菌活性。结果表明,NCD-2菌株和突变子MS周围能形成清晰的透明圈,而突变子MF周围透明圈模糊,说明fengycin对大丽轮枝菌具有抑菌活性。不同浓度的脂肽提取物对大丽轮枝菌孢子萌发的抑制试验表明,NCD-2野生型菌株的脂肽提取物能抑制大丽轮枝菌孢子萌发,在0.1 mg·mL^-1浓度下对孢子萌发的抑制率为46.30%,且随着脂肽浓度的提高抑制效果更加明显;同野生型菌株相比,突变子MF脂肽提取物显著降低了对大丽轮枝菌孢子萌发的抑制效果,在0.1 mg·mL^-1浓度下对孢子萌发的抑制率仅为18.48%,而突变子MS的脂肽提取物对大丽轮枝菌孢子萌发抑制效果与野生型菌株没有显著差异。通过测试脂肽提取物对微菌核形成的影响,发现野生型菌株和突变子MS脂肽提取物均能够显著抑制微菌核的形成,而突变子MF几乎丧失了对微菌核形成的抑制作用。RT-qPC...

Effect of fengycin produced by Bacillus subtilis NCD-2 on the conidial germination and microsclerotia formation of Verticillium dahliae

Bacillus subtilis strain NCD-2 could produce lipopeptides fengycin and surfactin,and showed significant biocontrol effect on cotton verticillium wilt.Antifungal activities of NCD-2 wild type,fengycin-deficient mutant (MF) and surfactin-deficient mutant (MS) strains against Verticillium dahliae were compared by using double layer medium method.Results showed that clear inhibitory zone could be formed around the wild type strain and the mutant MS,but not around the mutant MF.It was indicated that fengycin contributed to the antifungal activity against V.dahliae. Germination inhibition of V.dahliae conidia by lipopeptide extracted from strain NCD-2 was evaluated.Results showed that different concentrations of the lipopeptide had different inhibition effects on conidial germination,and with the increase of lipopeptide concentration,the suppression became more obvious.At 0.1 mg·mL^-1 concentration,the lipopeptide extracted from wild type strain could inhibit the conidial germination by 46.30 %,however,only 18.48 % inhibitory rate was achieved by the lipopeptide from mutant MF.The inhibitory effect of lipopeptide extract from mutant MS was similar to that of the wild type strain.Effects of lipopeptides from the different strains on microsclerotia formation was also evaluated.Results showed that the lipopeptides from wild type strain and mutant MS significantly suppressed microsclerotia formation.However,the lipopeptide from mutant MF almost lost the inhibitory ability on microsclerotia formation.Further RT-qPCR experiment convinced that the lipopeptides from the wild type strain and mutant MS could inhibit expressions of genes related to microsclerotia formation.However,the lipopeptide from mutant MF lost the inhibition ability.Taken together,it was confirmed that fengycin played an important role in suppressing conidia germination and microsclerotia formation of V.dahliae.