STUDIES OF PARASPORAL BODY FORMING BACILLI

苏云金芽孢杆菌的特点是产生大量的， 孢子形成过程中的细胞内包涵体。其中的每一项都是 由一类或几类大的多肽(原毒素)组成 对特定种类的昆虫幼虫是有毒的。有一种光谱 这些毒素由苏云金杆菌亚种产生，每个亚种都有独特的 对某些昆虫幼虫的毒性模式。其中包括 许多对农作物和树木造成重大损害的昆虫(鳞翅目)以及 其他作为人类疾病携带者的，如蚊子和 苍蝇。在一些亚种中，形成了不止一个包裹体，每个包裹体 含有一种独特的毒素。这些多肽是在一段时间内产生的 形成孢子的过程，并包含蛋白质的相当一部分 形成期的合成活动。 其中几个原毒素基因已经从苏云金杆菌中克隆出来。 枯草杆菌穿梭表达载体的构建及高效表达 在两种生物体中都允许确定选定的致死剂量 新生幼虫。毒素特异性的基础将由以下因素确定 苏云金芽胞杆菌亲本克隆株相对Lc50‘S的比较 原毒素基因(单独或组合)和蜡样芽胞杆菌透性芽孢杆菌 含有选定的苏云金芽胞杆菌质粒阵列。苏云金芽胞杆菌 我们将选择亚种和克隆的基因来进行比较。 既有重叠的，也有非重叠的。各地区 将对克隆的原毒素基因进行亚克隆以检测毒性水平 以及特异性的变化。 至少在一个亚种中对原毒素合成的调节是 依赖于两个隐蔽质粒的活性。一种质粒会影响 原毒素合成的温度，另一个是产生量。 将利用克隆的原毒素基因和 克隆这些调控质粒的片段，以确定 每一个参与调控的质粒区，是否存在基因 产品以及监管功能是否处于 抄写或其他地方。

Bacillus thuringiensis is characterized by the production of a large, intracellular inclusion during sporulation. Each of these inclusions is comprised of one or a few classes of large polypeptides (protoxins) that are toxic for specific species of insect larvae. There is a spectrum of these toxins produced by subspecies of B. thuringiensis each with a unique pattern of toxicity for certain insect larvae. Included among these are many that cause major damage to crops and trees (Lepidoptera) as well as others that serve as carriers of human diseases, i.e. mosquitoes and flies. In some subspecies, more than one inclusion is formed and each contains a unique toxin. These polypeptides are produced during a portion of the sporulation process and comprise a substantial part of the protein synthetic activity during the period of formation. Several of these protoxin genes have been cloned from B. thuringiensis plasmids into B. subtilis E. coli shuttle vector and express sufficiently well in both organisms to permit determination of lethal doses for select neonate larvae. The basis for toxin specificity will be determined by comparing relative LC50's for parental B. thuringiensis strains, cloned protoxin genes (alone or in combination) and of B. cereus transcipients containing selected arrays of B. thuringiensis plasmids. B. thuringiensis subspecies and cloned genes will be chosen to provide a comparison of those with overlapping as well as non-overlapping specificities. Various regions of the cloned protoxin genes will be subcloned to examine toxicity levels as well as alterations in specificity. The regulation of protoxin synthesis in at least one subspecies is dependent on the activities of two cryptic plasmids. One plasmid affects the temperature of protoxin synthesis, the other the amount produced. Bioassay systems will be developed employing cloned protoxin genes plus cloned fragments of these regulatory plasmids in order to define the portion of each plasmid involved in regulation, whether there is a gene product and whether the regulatory function is at the level of transcription or elsewhere.