Essay 22 Bacillus thuringiensis and Its UsesWords1 B. thuringiensis (Bt) n. 苏云金杆菌 2 insecticidal adj.杀昆虫的, 杀昆虫剂的 3 Lepidoptera n. 鳞翅目 4 mosquito larvae n. 蚊子幼虫 5 simuliid blackfly 呐黑蝇 6 vector v向带菌 7 fungicide n. 杀真菌剂 8 herbicide n. 除草剂 9 insecticide n. 杀昆虫剂 10 biocontrol agent n. 生物防治剂 11 host range n. 宿主范围 12 Bacillus popilliae n.（日本）金龟子芽孢杆菌 13 aggregate n. 聚合体 14 kDa n. （分子量单位）千道尔顿（kilodalton） 15 protoxin n. 原毒素16 mid-gut n. (昆虫)中肠 17 protease n. 蛋白酶 18 delta-endotoxin n. 德耳塔内毒素 19 epithelial cell n.上皮细胞 20 immobilize v. 固定 21 lyse v. 细胞裂解 22 septicaemia n.败血病 23 domain n .结构域 24 beta-sheet n. beta-（折叠）片层 25 antigen-binding region n. 抗原结合区 26 immunoglobulin n. 免疫球蛋白（即抗体） 27 beta-sandwich n. beta-（折叠）片层构成的夹心 28 C-terminus n. C-末端，羧基末端 29 diphtheria toxin n.白喉毒素 30 flour moth n. 面粉蛾31 Thuringia n. 图林根州德意志联邦共和国州名32 potent adj. 强力的，有力的, 有效的33 B. thuringiensis var kurstaki 苏云金杆菌库斯塔变种4 formulation n. 配方35 screen v. 筛选36 coleopteran n. 鞘翅类37 diptera n. 双翅类38 B. thuringiensis var aizawai苏云金杆菌鲇泽变种39B.t. var israelensis苏云金杆菌以色列变种40 gnat n. 小昆虫。 Fungus gnats（蕈蚊）: 小形双翅蝇构成蕈蚊科和尖眼蕈蚊科任何一种,具有取食真菌的幼虫。41 Aedes n.伊蚊(一种传染黄热病的蚊子)42 Culex spp. 库蚊亚种 (常见于北美、欧洲)43 Anopheles spp. 按蚊亚种44 B.t. var san diego n.苏云金杆菌圣地牙哥变种45 B.t. var tenebrionis n.苏云金芽胞杆菌拟步行甲变种46 Colorado potato beetle n. 科罗拉多薯虫 47 Cry (crystal) toxin n. 晶体毒素 48 Cyt (cytolytic) toxin n. 细胞裂解毒素 49 augment v. 增加, 增大 50 sequence similarity n. 序列相似性 51 bipyramidal adj. 双棱锥的 52 cuboidal adj. 立方形的 53 transposon n. 转座子 54 flank vt.在.的侧面, 侧翼包围, 守侧面 55 aubergine n.茄子, (茄子般的)紫红色 56 Solanaceae n. 茄科 57 gene pyramiding n. 基因聚合。就是将分散在不同品种中的优良性状基因通过杂交、回交、复合杂交等手段聚合到同一个品种中。 58 encouraging adj. 令人鼓舞的 59 aminopeptidase n. 氨基肽酶 60 bore v. 钻 61 European corn borer n. 欧洲玉米钻心虫 62 downside n. 底侧，下降趋势 63 selection pressure n. 选择压力 B. thuringiensis (commonly known as Bt) is an insecticidal bacterium, marketed worldwide for control of many important plant pests - mainly caterpillars of the Lepidoptera (butterflies and moths) but also mosquito larvae, and simuliid blackflies that vector river blindness in Africa. Bt products represent about 1% of the total agrochemical market (fungicides, herbicides and insecticides) across the world. The commercial Bt products are powders containing a mixture of dried spores and toxin crystals. They are applied to leaves or other environments where the insect larvae feed. The toxin genes have also been genetically engineered into several crop plants. The method of use, mode of action, and host range of this biocontrol agent differ markedly from those of Bacillus popilliae.Text苏云金杆菌（常称为Bt）是一种杀昆虫细菌，在全世界范围内销售，用于许多作物 虫的控制， 主要是鳞翅目（蝶和硪）的毛虫、蚊子幼虫、以及在非洲的江河中泛滥 流行的呐黑蝇。Bt产品占全世界农化市场（杀真菌剂，除草剂和杀昆虫剂）的1%。 商业Bt产品是含干燥孢子和毒素晶体混合物的粉末。可施用在叶片上或其它昆虫幼 虫取食的环境中。毒素基因也已经遗传工程化到数种作物中了。此种生物防治剂的使 用方法、作用模式和宿主范围与（日本）金龟子芽孢杆菌明显不同。Mode of action The crystals are aggregates of a large protein (about 130-140 kDa) that is actually a protoxin - it must be activated before it has any effect. The crystal protein is highly insoluble in normal conditions, so it is entirely safe to humans, higher animals and most insects. However, it is solubilized in reducing conditions of high pH (above about pH 9.5) - the conditions commonly found in the mid-gut of lepidopteran larvae. For this reason, Bt is a highly specific insecticidal agent. 作用模式晶体是大的蛋白质（约130-140千道尔顿）的聚集体，实质上是一种原毒素，必须先经过活化才有作用。此种晶体蛋白在正常条件下是高度不溶于水的， 因此对人类、高等动物和大多数昆虫是完全安全的。但是在高pH（高于大约pH 9.5）和还原条件下溶解性增强， 此种条件通常存在于鳞翅目昆虫幼虫的中肠中。正是由于这个原因，Bt是一种高度特异的杀昆虫剂。Once it has been solubilized in the insect gut, the protoxin is cleaved by a gut protease to produce an active toxin of about 60kD. This toxin is termed delta-endotoxin. It binds to the midgut epithelial cells, creating pores in the cell membranes and leading to equilibration of ions. As a result, the gut is rapidly immobilized, the epithelial cells lyse , the larva stops feeding, and the gut pH is lowered by equilibration with the blood pH. This lower pH enables the bacterial spores to germinate, and the bacterium can then invade the host, causing a lethal septicaemia.一旦在昆虫的肠道中溶解，原毒素就通过肠蛋白酶的切割产生大约60kD的有活性的毒素。此毒素称为德耳塔内毒素。它可与中肠上皮细胞结合，在细胞膜上产生孔洞，导致离子的平衡。结果，中肠被快速固化，上皮细胞裂解，幼虫停止取食，中肠 pH与血液pH达成平衡而降低，此降低了的pH使细菌孢子萌发，产生的细菌又浸染宿主，引起致命性的.败血病。Recent studies on the delta-endotoxin structure show that it has three domains . Dom