中文摘要：

为明确枯草芽胞杆菌BacillussubtilisNCD-2菌株生物膜形成相关基因及其在生物膜形成、根际定殖中的作用，采用转座子插入技术，从4000余株NCD-2突变子中获得6株生物膜形成能力降低的突变子。在生物膜形成能力丧失的突变子M3中，转座予以单拷贝的形式插入到ywbB基因内部。通过基因同源重组技术对ywbB基因进行缺失突变，获得ywbB基因缺失突变菌株NCD-2（AywbB），与野生菌株相比，突变子丧失了生物膜形成能力。进一步比较发现，突变菌株NCD-2（AywbB）显著降低了在棉花根际的群体数量，同时也降低了对棉花立枯病的防治效果。研究证明，ywbB是NCD-2菌株生物膜形成途径中的重要基因，且生物膜形成与NCD-2菌株根际定殖和生防效果呈正相关。

英文摘要：

Bacillus subtilis NCD-2 is a plant beneficial bacterium which forms biofilm in vitro and in plan- ta. In order to elucidate the role played by biofilm formation and its associated gene （s） in the rhizo- sphere colonization and bio-control capability of Bacillus subtilis NCD-2, a Tn-lO transposon mutant li- brary of strain NCD-2 was constructed in this study. Six out of 4 000 mutants showed deficiency in biofilm formation. The mutant strain M3, which was dramatically lost the capability of biofilm formation, was fur- ther studied. Gene ywbB was identified which was inserted by the transposon Tn-lO with a single copy in mutant strain M3. A deletion mutant of ywbB, mutant strain NCD-2 （AywbB）, was generated to charac- terize the role of ywbB in strain NCD-2. Compared with the wild strain NCD-2, mutant strain NCD-2 （AywbB） also showed deficiency in biofilm formation. Meanwhile, mutant strain NCD-2 （AywbB） de- creased the ability of colonization in cotton rhizosphere and control against cotton seedling rhizoctoniadamping-off. The results confirmed that ywbB was an strain NCD-2. It was suggested that biofilm formation tion and disease control of strain NCD-2. important gene among biofilm was positively correlated with formation pathway in rhizosphere coloniza-