Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Science Bt toxins Bt toxins What is this Bt toxin that is in the food we eat? Bacillus thuringiensis is an insecticide with unusual properties witch make it very useful for pest control in certain situations. Bacillus thuringiensis is a naturally occurring bacterial disease in some insects. It is very common in the soils around the world. There are many strains of Bt that can infect insects and kill them. The Bt toxin has been developed because of this unusual property. The insecticidal properties of Bt were first discovered in 1911. The commercial use, although, was not available until the mid-fifty’s. In recent years, there has been renewed interest in Bt and several new products have been developed, because of the human safety associated with Bt-based insecticides. Also, strains of this bacterium have been produced to affect certain fly larvae, such as mosquito’s and leaf beetles. Although the Bt toxin is used worldwide it does have its down side. Bt-based products tend to have a shorter shelf life than other insecticides. Manufacturers indicate that it has reduced effectiveness after two to three years of storage. Shelf life is greatest when it is stored in cool, dry areas that are out of direct sunlight. Bt is also very susceptible to degradation by sunlight Most formulations only stay active for less than a week following the application. With some of the newly developed strains, there has been even shorter persistence lasting less than twenty-four hours. The manufacturers have been experimenting with several ways to increase the longevity of the Bt toxin after the application. One of these involves inserting Bt toxin crystal genes into other species of bacterium that can better survive on the surfaces of crops. The specific activity of Bt limits their use on crops where several pests are present. Bt functions as a stomach poison insecticide. Thus it has to be eaten and the application must cover as much of the plant to be effective. This also poses more limits because some pests that are highly effected rarely get a chance to eat it, such as the codling moth and the corn earworm that tunnel into the plant. Recently the use of additives (stickers, wetting agents) is often useful in Bt applications to improve the performance, making it able to completely cover an area and resist washing of in watering. Since Bt doesn’t cause an instant kill some people assume that the pesticide is ineffective after a day or two. This is, however, just a perceptual problem. The Bt infected insects may eat very little or nothing at all before they die. On the other hand, the specific potency of Bt is considered to be highly beneficial. Because Bt toxins don’t have a very broad band spectrum, beneficial insects, such as bees, are not affected. This also includes the natural predators and parasites that feed of the insects. Therefore, Bt can use can integrate well with other natural controls when trying to control the pests. In Colorado the use of Bt to control the corn borers in field corn has been mostly stimulated the fact that it controls two types of pests. Corn borers are the natural enemy of the Spider mite. Mite infestations usually occur after the corn borers have been wiped out. The Bt toxin effects both of these pests. Because Bt is safe for humans and wildlife, it has a major advantage over other pesticides. This high margin of safety recommends its use on crops or other sensitive sights where pesticide use can cause adverse effects. The exceptional safety of Bt products makes them useful where exposure to the pesticide during mixing and application is likely. Scientists now have been genetically engineering Bt into corn crops. Plant geneticists create Bt corn by inserting selected exotic DNA into the corn plant's own DNA. DNA is the genetic material that controls the alleles of a plant or animal’s trait. Seed companies select elite hybrids for the Bt transformation in order to retain important agronomic qualities for yield, harvestability and disease resistance. Three primary components of the genetic package inserted into corn; protein genes, promoters, and genetic markers. Protein genes, Bt genes modified for improved expression in corn, produce Cry proteins. Initial Bt hybrids in the United States and Canada includes one of three Cry proteins, Cry1Ab, Cry1Ac or Cry9C. Future hybrids may produce other Cry proteins, or proteins from other sources. A promoter controls where and how much of the Cry protein a plant produces. Some promoters limit protein production to specific parts of the plant (for example, leaves, green tissue and pollen) whereas others produce protein throughout the plant. The presence of a genetic marker allows seed companies to identify successful transformations. Current examples of markers include genes for herbicide resistance or antibiotic resistance. Bibliography: Word Count: 792
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