Parasporal Body of Bacillus thuringiensis israelensis
Parasporal Body of Bacillus thuringiensis israelensis
复制标题
以色列苏云金芽孢杆菌的伴孢体
DOI：
10.1007/978-94-011-5967-8_3
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发表时间：
1990
影响因子：
4.1
通讯作者：
J. Ibarra
中科院分区：
文献类型：
--
作者：
B. Federici;P. Luthy;J. Ibarra
自从本世纪初在日本和德国发现苏云金芽孢杆菌以来，已经描述了超过25种形成孢子的杀虫细菌苏云金芽孢杆菌(de Barjac，1985)。这种细菌最显著的特征是在孢子形成过程中产生的伴孢体，主要由杀虫蛋白组成(Angus 1965；Heimpl 1967；Aronson，Beckman和Dunn 1986；Hofte和Whiteley 1989)。在大多数亚种中，伴孢体是一个双锥体晶体，含有一个或多个约135 kDa的类似蛋白，对鳞翅目幼虫具有毒性。当幼虫摄入时，这种含毒素的包含物溶解在碱性肠液中，中肠蛋白酶裂解原毒素，产生一种60-70 kDa的活性多肽毒素，即δ-内毒素。虽然毒素的确切作用模式尚不完全清楚，但中毒会导致中肠上皮细胞膜渗透失衡，从而迅速导致中肠细胞肥大和溶解。溶解之后，基底膜破裂，消化液渗入血腔，幼虫死亡(Luthy和Ebersell 1981)。苏云金芽胞杆菌不同亚种的δ内毒素对幼虫的毒性差异很大。这些变异被认为是由于毒素的氨基酸序列的差异，目前引起了人们的极大兴趣，因为通过定点突变可能会增加毒性和宿主谱。
Since its discovery in Japan and Germany during the early part of this century, more than 25 subspecies of the spore-forming insecticidal bacterium Bacillus thuringiensis Berliner have been described (de Barjac 1985). The most distinctive characteristic of this bacterium is a parasporal body produced during sporulation that consists primarily of insecticidal proteins (Angus 1965; Heimpel 1967; Aronson, Beckman, and Dunn 1986; Hofte and Whiteley 1989). In most subspecies, the parasporal body is a bipyramidal crystal containing one or more similar proteins of about 135 kDa that are toxic to lepidopterous larvae. When ingested by a larva, this toxin-containing inclusion dissolves in the alkaline gut juices, and midgut proteases cleave the protoxin, yielding an active peptide toxin of 60–70 kDa, the δ-endotoxin. Although the toxin’s precise mode of action is not fully understood, intoxication results in an osmotic imbalance across the midgut epithelial cell membrane, which leads quickly to hypertrophy and lysis of midgut cells. Lysis is followed by disruption of the basement membrane, leakage of digestive juices into the hemocoel, and larval death (Luthy and Ebersold 1981 ). The δ-endotoxins of different subspecies of B. thuringiensis can vary considerably in toxicity to larvae. These variations are thought to be due to differences in the amino acid sequence of the toxins, and are currently the subject of much interest because of the potential for increasing toxicity and host spectrum through site-directed mutagenesis.