Changes in survival, mean dry weight, levels of key energy reserve compounds and respiration of non-feeding infective juveniles (IJs) of Steinernema carpocapsae incubated in various ratios of D2O:H2O on a shaker at 28

Permeability of the sheath and cuticle of the infective juveniles (IJs) of Steinernema carpocapsae to glycerol and its effect on biochemical adaptation of the IJs to osmotic dehydration were examined by incubating both sheathed and exsheathed IJs in glycerol-d5 solution then monitoring the changes in levels of deuterium labelled and non-labelled glycerol and trehalose. Energy metabolism of the IJs during osmotic dehydration and subsequent rehydration and the effect of the permeated glycerol on this process were investigated by examining and comparing the changes in mean dry weight and key biochemical composition of the IJs dehydrated in glycerol and sodium chloride solutions. The results show: (1) similarly to evaporative dehydration, osmotic dehydration induces IJs to synthesise the protectants glycerol and trehalose; (2) glycerol permeates the sheath and the cuticle into the body of IJs during dehydration in glycerol solution. Part of the permeated glycerol plays a role as protectant like that synthesised by IJs from their energy reserve materials while part is incorporated into trehalose; (3) the sheath reduces the rate of permeation of glycerol and therefore affects the equilibrium glycerol and trehalose levels of the IJs and also the time needed to reach the equilibrium levels; (4) the reduction in mean dry weight and lipids of the IJs during dehydration in glycerol solution is substantially less than those dehydrated in sodium chloride solution. Both the total protectant level and the ratio of glycerol to trehalose of the IJs dehydrated in glycerol solution are higher than those dehydrated in sodium chloride solution; (5) glycogen reserves of the IJs play a role as a buffer reservoir of the protectants during both dehydration and rehydration but the principal sources of the protectants during dehydration are more likely to be lipids and proteins rather than glycogen.

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。