对昆虫病原线虫共生菌杀虫毒素的种类，与口服毒性有关的杀虫毒素以及口服毒性与杀虫毒素基因的关系等研究进展进行了综述，并对未来的研究方向提出了作者的见解。

昆虫病原线虫共生菌xenorhabdus nematophilus BP的多个杀虫毒素基因集中在一起形成一个约40kb的基因簇。为研究这个基因簇中各基因与杀虫活性的关系对该共生菌粘粒文库中5个粘粒克隆XnBP76、XnBP83、XnBP203和XnBPD378和XnBP414及XnBP83的3个亚克隆插入DNA片段的基因结构和它们对棉铃虫的杀虫活性进行了比较，结果显示xptB1，xptC1和xpt3个基因或后两者的联合表达产物具有最强的杀虫效果，缺失其中的任何1个或2个会使杀虫活力大幅度地下降或完全消失，而xptd1的缺失对毒素基因簇的表达产物的杀虫活力影响很小；杀虫毒素的物理混合没有明显的增效作用。

构建了昆虫病原线虫共生菌Xenorhabdus nematophilus BP品系的粘粒文库并用生物测定的方法从中筛选到2个对棉铃虫初孵幼虫有口服抑杀作用的克隆cos83和cos76。为初步确定这两个克隆的毒素基因与已报道基因的差异程度，根据已发表的共生菌毒素基因序列资料设计了7对引物对这两个克隆进行PCR扩增并对扩增产物进行测序和分析。从毒力较强的cos83中7对引物均扩增出与目标片段大小一致的产物而从cos76中只有5对扩增到目标片段。测序结果显示cos76的5个PCR扩增产物与cos83的对应扩增产物DAN序列同源性为100%。以cos83的7个PCR扩增产物所编码氨基酸序列进行BLAST分析，它们与X. nematophilus PMF1296和Photorhabdus luminencenc W14毒素相应区间的平均同源性分别为94%和58%说明cos83毒素是共生菌口服毒素家族的一员但与同类的其它毒素有一定的差异，值得对其杀虫谱，作用机理等进行进一步的研究。

A new species of entomopathogenic nematode, Steinernema guangdongense sp. n. was recovered from a soil sample collected from Jijia town in the western part of Guangdong province, the Peoples Republic of China during a survey for entomopathogenic nematodes in 2001. The nematode can be separated from other described species of Steinernema, by morphological, morphometrical characteristics of different stages of the nematode, by crossbreeding tests and by characterizations and phylogeny of DNA sequences of either a partial 28S or the internal transcribed spacer regions of rDNA. This nematode is closest to S. longicaudum. It can be distinguished from that nematode by characteristics of different stages. For infective juveniles, although the body length is almost similar (1055 μm compared to 1063μm), body diameter of the new species is larger; values of EP (length from anterior end to excretory pore), NR (length from anterior end to nerve ring) and a body length/body width ratio are smaller, and tail with dorsal constriction. For male, the new species has longer spicule, not well curved, spicule head shorter, shaft not prominent or absent and spicule tip not suddenly tapered as shown in S. longicaudum. Also, the ratios SW (spicule length/anal body width) and GS (gubernaculums/spicule) are smaller. For female, the presence of a small double flapped epiptygma, a small projection on dorsal side of the tail tips and prominent post-anal swelling is typical for the new species.