乙偶姻和枯草芽孢杆菌NRCB002的促生机制

【目的】研究植物根际促生菌及其代谢产物对作物生长的促进效应及其机制，为制备高效微生物肥料提供优良的菌种资源和应用技术支持。【方法】枯草芽孢杆菌枯草亚种(Bacillus subtilis subsp. subtilis)NRCB002发酵液组分的促生效应盆栽试验设置了5个处理，分别为发酵培养基(P)、发酵菌液(F)、发酵菌液上清液(S)、重悬菌液(G)和重悬菌液+乙偶姻(A)，以浇灌等量的去离子水的处理为对照(CK)。进一步的乙偶姻施用方式盆栽试验设置两个处理，分别为在生菜幼苗根部浇灌(RI)、叶面喷施(FS) 0.1 g/L乙偶姻溶处理，以施用等量去离子水的处理为对照(CK)。生菜生长两周后，两组盆栽试验收获地上部及根系，测定株高、叶面积、地上部和根部的鲜重和干重，并分析根系指标。以K氏培养基为基础培养基，添加0、0.075、0.375、1.5 g/L的乙偶姻培养NRCB002，采用结晶紫染色法测定了NRCB002生物膜的形成量。【结果】1)与CK相比，除培养基P处理外，其余4个处理均显著提高了生菜幼苗的地上部和根部的鲜、干重；S、F和A处理还显著增加了生菜幼苗的株高、叶面积、总根长...

Mechanism of growth promotion by acetoin and Bacillus subtilis NRCB002

  【Objectives】  This study was conducted to explore the promoting effect of plant growth promoting rhizobacteria and their metabolites on crop growth, and deeply understand the mechanism of their promoting crop growth, so as to provide excellent strain resources and technical support for the application of efficient microbial fertilizer.  【Methods】  A pot experiment was carried out to clarify the growth-promoting effect of the fermentation broth components of Bacillus subtilis subsp. subtilis NRCB002. Five treatments were set up, namely fermentation medium (P), fermentation broth (F), fermentation broth supernatant (S), resuspended bacteria (G) and resuspended bacteria + acetoin (A) respectively, and the control treatment was irrigated with the same amount of deionized water (CK). Another pot experiment on the growth-promoting effect and application methods of acetoin was conducted. Two treatments of root irrigation (RI) and foliar spray (FS) with 0.1 g/L acetoin solution were set up, with the same amount of deionized water as the control (CK). Two weeks after treatment imposition in both studies, lettuce seedlings were characterized for plant height, leaf area, fresh and dry weights of shoot and root, and root index. NRCB002 was cultured under K medium with 0, 0.075, 0.375, and 1.5 g/L acetoin addition. The amount of NRCB002 biofilm formation was determined by crystal violet staining method.   【Results】  1) Compared with CK, fresh and dry weight of shoot and root were significantly increased by the other four treatments except for the P treatment. Treatments of S, F, and A also significantly increased the plant height, leaf area, total root length, total root surface area, total root volume and number of lateral roots of lettuce seedlings. Except for average root diameter and number of lateral roots, the growth characteristics of lettuce seedlings treated with S, F, and A were similar, S, F and A treatments significantly enhanced shoot dry weight, fresh and dry weight of root compared with G treatment. 2) Compared with the control, plant height, total root length, total root surface area, total root volume, number of lateral roots, root-shoot ratio, fresh and dry weight of shoot and root of lettuce seedlings treated with root application (RI) and leaf application (FS) of acetoin were significantly increased. Except for root dry weight and root-shoot ratio, there was no significant difference between the two treatments. 3) Acetoin significantly increased the biofilm formation of NRCB002. Under three application concentrations, the biomass of NRCB002 were similar, but the biofilm formation of NRCB002 with acetion of 0.375 g/L was significantly lower than that with acetion of 0.075 and 1.5 g/L.   【Conclusions】  Acetoin is a key promoting component of NRCB002 fermentation broth. Root irrigation and foliar spray, especially foliar spray of trace amounts of acetoin directly promotes the growth of lettuce seedlings. Acetoin significantly enhances the biofilm formation of NRCB002, which would improve the stability of NRCB002, therefore acetoin and NRCB002 have synergistical effects.