苏芸金杆菌伴孢晶体和芽孢孢衣的蛋白质组分及其与毒力的关系

研究了苏芸金杆菌(Bacillus thuringiensis)3个变种6个菌株的提纯伴孢晶体和芽孢对大蜡螟(Galleria mellonella)和大菜粉蝶(Pieris brassicae)的毒力、晶体的蛋白质和多肽成分及芽孢衣中的类晶体蛋白质成分.生物测定表明,晶体毒力高于芽孢,在总数量相同的情况下,晶体和芽孢近1:1的混合物的毒力高于单独的晶体或芽孢.芽孢衣中存在一种类似晶体蛋白质的成分,无晶体突变株及无效野生株的芽孢则无此种蛋白质且对两种昆虫无毒.变种wuhanensis和变种galleriae的晶体含MW138000的主要蛋白质和63000的次要蛋白质,经碱性缓冲液溶解后,上清液含MW138000的蛋白质,沉淀中含MW63000的蛋白质;变种aizawai的晶体中仅含138000的蛋白质.对大蜡螟无毒的HD-11(var.aizawai)晶体的蛋白质成分有别于上述晶体,其胰蛋白酶消化物的SDS凝胶电泳图型显示少2条多肽带,但对大菜粉蝶仍有效.结果表明,苏芸金杆菌的芽孢在昆虫病理中有重要作用,伴孢晶体的蛋白质和多肽成分与它们对昆虫的毒力特性之间有密切关系.

THE COMPOSITION OF PROTEINS AND POLYPEPTIDES IN CRYSTALS AND SPORE COATS OF BACILLUS THURING1ENSIS AND THEIR TOXICITY TO INSECTS

The toxicity of pure spores and parasporal crystals from 3 variants of Bacillus ihuringi-ensis was tested in Calleria mellonella and Pier is brassicae. The composition of proteins and polypeptides in crystals and spore coats was; investigated simultaneously. Bioassays indicated that strains HD-282, 8-25 and 140 were-potent against the larvae of Galleria mellonella. Crystals were more efficient than spores, but the .mixture of spore/crystal in ratio of 1:1 showed the highest toxicity.A protein with MW 138000 similar to the main protein in crystals was present in the spore coats of 3' wild strains, but spore coats of an acrystalliferous mutant and an inactive wild strain lost this specific protein and they also lost toxicity to both insects. Some difference was found to exist in the patterns of proteins and polypeptides of crystals from the strains of var. wu-hanensis, var. galleriae and var. aizawai. There were an alkali-dissoluble protein of Mr 138000 (P-1) in supernatants and an alkali-indissoluble protein of MW-63000 (P-2) in pellets, when the crystals of 8-25 (var. galleriae) and 140 (var. wuhanensis) were abstracted by Na2CO3-HC1(0.1 M, pH 9.5).It was shown that there was a direct relation between the composition of proteins and . polypeptides in crystals and spore coats of Bacillus thuringiensis and their toxicities against insects.