两株苏云金芽孢杆菌的基因鉴定及形态和杀蜱作用观察

目的鉴定两株苏云金芽孢杆菌的形态、杀虫基因种类,并评估其杀蜱作用。方法培养两株苏云金芽孢杆菌,显微镜下观察其形态。将长角血蜱饱血幼蜱浸渍于芽孢浓度为10~8CFU/ml的菌液中,观察死亡率。PCR方法检测两株苏云金芽孢杆菌的Cry和Cyt类杀虫基因。结果发酵后的Bt.Kustaki株较Bt(GIM 1.150)株有更多的晶状体。浸渍Bt(GIM 1.150)株饱血幼蜱死亡率为21.67%,与对照组死亡率5.00%比较差异有统计学意义(P<0.05);浸渍Bt.Kustaki株,饱血幼蜱死亡率为7.33%,与对照组比较无统计学意义(P>0.05)。Bt.Kustaki仅检出Cry2类基因,Bt(GIM 1.150)检出6个Cry和Cyt类基因。结论苏云金芽孢杆菌对长角血蜱幼蜱有毒杀作用,杀蜱效果可能与其发酵形态和杀虫基因有关。

Genetic identification of two strains of Bacillus thuringiensis and observation of their morphology and tick-killing action

Objectives To identify the morphology and types of insecticidal genes of two strains of Bacillus thuring-iensis and to evaluate their tick-killing action.Methods Two strains of B.thuringiensis were cultured and their mor-phology was observed using microscopy.Fed larval Haemaphysalis longicornis ticks were immersed in a Bacillus solution with a spore concentration of 108 CFU/ml,and the mortality rate was observed.The Cry and Cyt genes of B.thuringiensis were detected using PCR.Results After fermentation,B.thuringiensis var.kustaki strains had more crystals than B.thuringiensis(GIM 1.150)strains.The mortality rate of ticks submerged in B.thuringiensis(GIM 1.150)was 21.67%,which differed significantly from the mortality rate of 5.00%in the control group(P<0.05).Ticks submerged in the B.thuringiensis var.kustaki strain had a mortality rate of 7.33%,which did not differ significantly from that in the control group(P>0.05).B.thuringiensis var.kustaki was found to have only the Cry2gene,while B.thuringiensis(GIM 1.150)had six Cry or Cyt genes.Conclusion Bacillus thuringiensis kills larval H.longicornis,and this action may be related to its morphology during fermentation and insecticidal genes.