Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden; Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan.
Department of Industrial Biotechnology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
Microbiol Res. 2019 Jun-Aug;223-225:129-136. doi: 10.1016/j.micres.2019.04.006. Epub 2019 Apr 22.
Heterobasidion annosum s.s. and H. parviporum are severe pathogens of conifers causing butt rot and root rot thus reducing the economic value of timber. Here, the antifungal activity of Bacillus subtilis isolate A18 against these two Heterobasidion species was investigated. Five different culture media with different culture age were investigated to study the effect of substrate composition and culture age for metabolite production. Bacterial cultures and cell-free culture filtrates were tested for antifungal activity. Inhibition of fungal growth was analysed using the agar disc-diffusion method. MALDI-TOF and LC-HRMS analyses were used to identify the antifungal metabolites. Substrate composition and age of culture were found to be active variables with direct effect on the antifungal activity of bacterial culture extracts. High anti-fungal activity was observed when B. subtilis was cultured in PDB, SGB and LB media for four days. Mass-spectrometry analysis showed the presence of lipopeptides in culture filtrates identified as members of the surfactins, polymixins, kurstakins and fengycins. A culture filtrate containing fengycin-type lipopeptides showed the highest bioactivity against Heterobasidion species. Bacterial cultures had higher bioactivity compared to their respective cell free culture filtrates. The results of the present study suggest that B. subtilis A18 is a powerful biocontrol agent against Heterobasidion infections of tree wounds and stumps.
密环菌 ss 和 H. 短密环菌是针叶树的严重病原体，可引起树干腐烂和根部腐烂，从而降低木材的经济价值。在这里，研究了枯草芽孢杆菌分离株 A18 对这两种密环菌的抗真菌活性。研究了五种不同的培养基，不同的培养年龄，以研究基质组成和培养年龄对代谢产物产生的影响。测试了细菌培养物和无细胞培养滤液的抗真菌活性。采用琼脂-disc 扩散法分析真菌生长抑制情况。使用 MALDI-TOF 和 LC-HRMS 分析鉴定抗真菌代谢物。基质组成和培养年龄是具有直接影响细菌培养物提取物抗真菌活性的活跃变量。当枯草芽孢杆菌在 PDB、SGB 和 LB 培养基中培养四天时，观察到高抗真菌活性。质谱分析显示，培养滤液中存在脂肽，鉴定为表面活性剂、多粘菌素、库斯塔金斯和丰原素的成员。含有丰原素型脂肽的培养滤液对密环菌表现出最高的生物活性。与各自的无细胞培养滤液相比，细菌培养物具有更高的生物活性。本研究结果表明，枯草芽孢杆菌 A18 是一种有效的生物防治剂，可防治树木伤口和树桩的密环菌感染。
