中文摘要：

枯草芽胞杆菌B006是一株防治黄瓜枯萎病的高效菌株,可产生脂肽类抗生素表面活性素surfactin和芬枯草菌素fengycin。为深入了解surfactin在根际的作用,本研究通过同源重组的方法将生防芽胞杆菌B006菌株中编码4′-磷酸泛酰巯基乙胺转移酶Sfp的sfp基因整合到不产生surfactin的模式菌株B.subtilis168（B168）基因组中,获得了重组菌株B168S。重组菌株B168S在1%淀粉平板上不水解淀粉,在5%血平板上产生透明溶血圈;HPLC-ESI-MS检测表明菌株B168S在牛肉膏蛋白胨培养液中培养48 h后可产生surfactin。平板对峙试验表明菌株B168S在黄瓜根分泌物培养基上对Fusarium oxysporum f.sp.cucumerinum（Foc）菌丝生长有一定的抑制作用,抑制率R2/R1为1.22;平板菌落计数法测定表明,将菌悬液（10^6 cfu/m L）浸泡90 min的黄瓜种子播种于无菌石英砂3 d后,菌株B168S在黄瓜根基部和根尖的定殖量分别为菌株B168的2-3倍和9-10倍;温室盆栽试验表明,黄瓜苗用浓度为10^6 cfu/m L的B168S和B168菌悬液蘸根后,移栽到接种Foc孢子（10^5孢子/g）的病土中,移栽后第3周菌株B168S和B168处理的防效分别为21.1%和17.9%;对不同高度黄瓜茎中Foc的组织分离结果表明,菌株B168S处理后Foc在黄瓜茎内蔓延的相对高度低于菌株B168和Foc处理。上述结果进一步明确了surfactin可明显促进芽胞杆菌在黄瓜根部的定殖,并通过抑制枯萎病菌的侵染和在黄瓜茎中的蔓延增强对黄瓜枯萎病的防治效果。

英文摘要：

B. subtilis B006 is an effective biocontrol bacterium of fusarium wilt diseases by producing surfactin and fengycin. To elucidate the function of surfactin in vivo, the complete sfp gene encoding protein of PPantransferase Sfp to activate the surfactin synthetase, was amplified from B. subtilis B006. A transformant strain B168 S was constructed through inserting the sfp gene into the B. subtilis strain 168 by using homologous recombination method. The recombinant B168 S did not hydrolyze starch on 1% starch medium, but producing hemolysis circle around its colonies on 5% blood plates. Detection by HPLC-ESI-MS showed that B168 S produced surfactin after 48 h growth in nutrient broth, while B168 did not. Strain B168 S suppressed the mycelial growth of Fusarium oxysporum f. sp. cucumerinum（Foc） on cucumber root exudate（CRE） medium plates with inhibitory rate 1.22. Colonization tests by dilution plating method indicated that the population of B168 S colonized on cucumber root bases and root tips increased by 2—3 times and 9—10 times in comparison with B168 at 3rd day after germination when cucumber seeds soaked with 10^6 cfu/m L bacterial suspensions for 90 mins were sown in quartz sand. Greenhouse experiments showed that control efficacy of B168 S and B168 against fusarium wilt disease was 21.1% and 17.9%, respectively, at the third week after transplantation of cucumber seedlings immersed with 10^6 cfu/m L bacterial suspensions and transplanted to the substrate inoculated with Foc at 10^5 spores/g of soil. The isolation of Foc from cucumber stems at different height showed that B168 S was able to suppress the infection and the spread of Foc in cucumber, compared with the control and B168 treatments. In a conclusion, surfactin promoted B. subtilis colonization on cucumber roots and played an important role in suppressing the infection and spread of Foc in cucumber.