苏云金芽胞杆菌(Bt)是使用最成功的微生物杀虫剂。已报道71个血清型，克隆到73个大类的760多个杀虫基因(cry)，不同的Cry能够毒杀500多种昆虫与多种线虫。作为昆虫和线虫病原菌，Bt还能产生大量的辅助活性成分。目前对Bt的认识仅限于少数Cry蛋白的杀虫活性与机制等方面，对于不同Bt之间的遗传差异，主效和辅助活性成分的分布，以及它们所反映出的与宿主之间的进化关系等问题不清楚。本项目拟以所有71个血清型的标准菌株，以及部分血清型的非标准菌株为材料，以比较基因组的方法，研究菌株之间的系统发育关系、遗传差异性及其影响因素。研究主效和辅助毒力因子的分布和进化规律，建立杀虫活性谱与毒力因子以及菌株系统发育之间的关系。并结合近缘种的基因组，为Bt在蜡状芽胞杆菌群中的分类地位提供新证据。本研究将为有针对性地寻找新Bt资源提供理论基础，也将深化我们对于Bt作为重要昆虫与线虫病原菌的起源与进化的认识。

The Bacillus thuringiensis is the most successful microbial pesticide and is also an important source of the genes for genetically modified (GM) plants. There are 71 serotypes (84 serovars) reported and more 760 genes of insecticidal crystal protein cloned. And these Cry proteins showed toxic to more than 500 insects and many nematodes. As an important pathogen to insects and nematodes, Bt can produce many other accessory virulence factors except for Cry. Up to now the researches about Bt have been mainly focused on the activities and action mode of Cry proteins, those on the genetic differences among different Bt strains, the distributions and dynamics of the major toxins and accessory virulence factors among the Bt population, and the co-evolution between Bt and its hosts based on these features are rarely reported. This project plans to use all the type strains of the 71 serotypes, and some other strains with known serotypes as material, through the methods of comparative genomics, to study the phylogenetic relationships, genetic differences among these strains and the determinants of these features. The relationships among activity profiles of Bt against insects, distributions and evolution of Bt toxins and virulence factors, and the phylogenies of these Bt population, were revealed by studying the distributions, dynamics and evolution of these factors among the whole Bt population. Combing with its related species, comparative genomics will provide new insight into the evolutionary position for the Bt species. This study will provide important theoretical principle for new Bt strain source isolation and differentiation, and can also improve the knowledge of the origin and evolutionary history of Bt species as the important insect pathogen.