Bizzarri Mariangela F, Bishop Alistair H
School of Science, University of Greenwich, Chatham Maritime, Kent, ME4 4TB, UK.
J Invertebr Pathol. 2007 Jan;94(1):38-47. doi: 10.1016/j.jip.2006.08.007. Epub 2006 Sep 26.
Two media were developed which specifically allow the cultivation of Bacillus thuringiensis while it is in the vegetative as opposed to the spore form. Using these media B. thuringiensis was shown conclusively for the first time to exist in an active form on the phylloplane. The profile of its appearance in vegetative and spore form was followed over a growing season on clover (Trifolium hybridum) in the field. Three simultaneous and sudden rises and declines of both spore and vegetative cell densities were observed. The most common other spore-former on these leaves was Bacillus cereus but the fluctuations in appearance of these two very closely related species were not co-incident. Using specific PCR primers a considerable diversity of cry toxin gene types was found in isolates that had been recovered in vegetative form ('vegetative isolates') with the majority possessing multiple delta-endotoxin genes while some had only one of those tested. Bioassays against a lepidopteran insect of purified delta-endotoxins showed that they were no more potent than those from a laboratory-adapted strain. PCR primers for an internal region of the vip3A gene produced amplification in 70% of the vegetative isolates compared to 25% of the laboratory-adapted strains tested.
开发了两种培养基，它们专门用于苏云金芽孢杆菌处于营养体而非孢子形式时的培养。利用这些培养基，首次确凿地证明了苏云金芽孢杆菌以活性形式存在于叶面上。在田间三叶草（杂种车轴草）的一个生长季节中，追踪了其营养体和孢子形式的出现情况。观察到孢子和营养体细胞密度同时出现三次突然的上升和下降。这些叶片上最常见的其他产孢菌是蜡样芽孢杆菌，但这两个密切相关物种的出现波动并不一致。使用特异性PCR引物，在以营养体形式回收的分离株（“营养体分离株”）中发现了相当多样的cry毒素基因类型，大多数含有多个δ-内毒素基因，而有些只含有所检测的其中一个。对一种鳞翅目昆虫进行的纯化δ-内毒素生物测定表明，它们的效力并不比来自实验室适应菌株的δ-内毒素更强。与25%的受试实验室适应菌株相比，vip3A基因内部区域的PCR引物在70%的营养体分离株中产生了扩增。
