Bacillus thuringiensis and Its Pesticidal Crystal Proteins

Abstract

SUMMARY During the past decade the pesticidal bacterium Bacillus thuringiensis has been the subject of intensive research. These efforts have yielded considerable data about the complex relationships between the structure, mechanism of action, and genetics of the organism’s pesticidal crystal proteins, and a coherent picture of these relationships is beginning to emerge. Other studies have focused on the ecological role of the B. thuringiensis crystal proteins, their performance in agricultural and other natural settings, and the evolution of resistance mechanisms in target pests. Armed with this knowledge base and with the tools of modern biotechnology, researchers are now reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit.

Tevaluation of transgenic event CBH 351 (StarLink) corn in pig

“…It carries a novel gene from a naturally occurring soil bacterium, Bacillus thuringiensis ssp. tolworthi, which encodes for a form of the Bt endotoxin known as the Cry9C protein (Schnepf et al 1998). Because the Cry9C protein was not digested completely in vitro by simulated gastric and intestinal fluids, and because it is a possible allergen for human beings, it was approved only as a feedstuff and for use in alcohol production in the USA (U.S. EPA, Federal Register 17687), and it was not approved by regulatory agencies in Japan for use of either food or feed.…”

Two specific membrane-bound aminopeptidase N isoforms from Aedes aegypti larvae serve as functional receptors for the Bacillus thuringiensis Cry4Ba toxin implicating counterpart specificity

“…Cry d-endotoxins produced by Gram-positive spore-forming Bacillus thuringiensis (Bt) are highly toxic toward a wide range of insect larvae [1]. Of particular interest, the Cry4Ba toxin from Bt subsp.…”

Manduca sexta (Lepidoptera: Sphingidae) cadherin fragments function as synergists for Cry1A and Cry1C Bacillus thuringiensis toxins against noctuid moths Helicoverpa zea, Agrotis ipsilon and Spodoptera exigua

“…Bacillus thuringiensis Berliner (Bt), a spore-forming, gram-positive bacterium, is the leading biorational pesticide. 1 Bt can be isolated from many environments, 2,3 and new Bt strains have been isolated from soil, 2,4 -6 leaves, 6,7 granaries 8 and insects 4 worldwide. During sporulation, Bt produces one or more deltaendotoxins or Cry proteins, which form insoluble inclusions known as insecticidal crystal proteins (ICPs).…”

“…Although a specific Bt toxin has a narrow spectrum of activity, many different types of Bt toxin have been characterized that have selective toxicity to different orders of insects. 1 Bt is a valuable alternative or supplement to integrated pest management programs that utilize synthetic chemical pesticide applications along with other control methods in commercial agriculture, forest management and mosquito control. It is also the main source of genes for transgenic expression in crops to provide pest control with few or no chemical pesticide applications.…”

“…A generally accepted mode of action for Cry toxins describes the sequential steps of protoxin activation, specific binding and cell toxicity. 1 Ingested ICPs are solubilized and activated to a toxic form by the insect's digestive fluids. After crossing the peritrophic matrix, activated toxins bind to specific proteins (i.e.…”