从我国不同地区采集118份土样，利用温度筛选法分离获得一株苏云金芽胞杆菌（Bacillus thuringiensis，简称Bt）6618，镜检观察发现该菌株能产生典型的菱形晶体，PCR分析表明其含有cry1类杀虫基因。采用SDS-PAGE和质谱分析发现该菌株主要产生130 kD原毒素，其组分由Cry1Ae和Cry1Ac原毒素组成。基因序列分析表明该菌株的cry1Ac基因为已知的cry1Ac1，而cry1Ae为新型杀虫基因。毒力生测表明该菌株对棉铃虫（Helicoverpa armigera）幼虫具有显著的杀虫效果。筛选获得的高毒力Bt菌株6618为丰富我国苏云金芽胞杆菌储备和研发新型高效生物杀虫剂提供了菌株资源。

118 soil samples were collected from different parts of our country and a new Bacillus thuringiensis strain 6618 was isolated by temperature screening method. This strain could produce typical bipyramidal crystal under microscope observation. PCR analysis showed that it contained cry1-type gene. SDS-PAGE analysis indicated that this strain expressed a major protein band about 130 kD, which was verified by mass spectrometry analysis to be the products of Cry1Ae and Cry1Ac protoxins. Sequence analysis showed that the cry1Ac gene in this strain was identical to the published cry1Ac1 gene, while the cry1Ae gene was found to be different from the known gene. The crystal-spore mixture of the strain 6618 exhibited high toxicity towards the larvae of Helicoverpa armigera. The isolated Bacillus thuringiensis strain 6618 with high toxicity will not only enrich the reserve of Bacillus thuringiensis strains of our country, but also provide resource for the development of new efficient biological pesticide.