What is Bt Corn?

Bt delta endotoxin

 3-D model of Bt crystals

First of all Bt stands for Bacillus thuringiensis which is a spore forming bacterium that produces crystal proteins that are toxic to many species of insects that eat the corn(WWW.users.rcna.com). Bacillus thurginiensis can be found almost anywhere in the world because it is distributed in the soil particles frequently when it is stirred up by the wind. There are over one thousand types of Bt that produce over 200 types of crystal proteins that are toxic against a wide variety of insects and even some invertebrates. The toxin they produce is called Bt delta endotoxin and the reason why it was chosen is because it is highly effective in controlling caterpillars. The manner in which this crystal protein works is that it binds to specific receptors in the insects’ intestine and creates holes in the lining and eventually they die. This protein is very specific and generally don’t harm insects such as beetle, flies, bees and wasps. Humans and other vertebrate don’t have the receptors in their intestine and therefore they are not affected by it. Bt is used largely in the agriculture especially by organic farmers because it is a natural protein and is biodegradable. It is applied on to crops by aerial spraying programs and also in transgenic crops.

Bt corn has genetically been engineered through Biotechnologyto produce the Bt toxin which is poisonous to insect that feed on it. Bt corn is a type of GMO because it has been genetically modified through the addition of gene from a different organism through biological technigues. The main target for the Bt corn are the European corn borer and they create the most damage during the larva sage.

History of Bt toxin

Bt toxin was first discovered by a Japanese biologist named Shigetane Ishiwatari when he was investigating what was causing sotto disease. The sotto disease was the sudden collapse disease that was occurring to silkworms and he isolated the bacteria Bacillus thuringiensis (Bt) in 1901. In later years Ernest Berliner isolated the bacteria that was responsible for the death of Mediterranean flour month in 1911. The bacteria that he isolated were the same bacteria that were isolated by Shigetane Ishiwatari, and he named it Bacillus thuringiensis after a German town Thuringia. Mr. Ishiwatari had named the bacteria Bacillus sotto in 1901 but it was over ruled and renamed Bacillus thurigiensis, and in 1915 Berliner reported that Bt created crystal but the function of the crystal was not known until later years.

The Bt pesticide was used by farmers since 1920 and was later commercialized spore based by France in 1938. The pesticide was called Sorine  and its first purpose was to kill flour moths. As the years passed more products were produced that contained Bt but they all had limitations. Some of the limitations are that the Bt toxins:

·         Were washed off from the leaves whenever it rained.

·         Degraded by the sun Ultra violet rays.

·         Most of the insects were not affected by the stand of Bt toxin that was used.

The reason why this occurred was because the strand that was begin used was only toxic to moth larvae only. Then in 1956 researchers, Hanny, Fitz-James and Angus discovered that the insecticidal activity was due to the parasporal crystals. Then in 1958 the U.S.A. started to use the Bt toxin commercially and was later registered as a pesticide in 1961. Until 1977 there was only thirteen  subspecies of toxin that were known and they only affect the moth larvae. Then in 1977 they discovered the first subspecies toxin that affected the flies (dipteran) species, then six years later in 1938 they discovered the strain of toxin that was lethal to beetles.

As the years when by farmers became more interested in Bt toxins because the insects were becoming resistant to synthetic pesticides. Also scientist and environmentalist became aware that the chemicals in synthetic pesticides were harming the environment and the ecosystem. Due to this concern the government and private industries started to fund research on Bt because it is environmentally friendly. Over the years over one thousand strains of Bt were discovered and the genes that encodes the toxin in the DNA is now known.  Thanks to advancements in molecular biology and biotechnology, it became feasible to replicate the gene in Bt that encoded for the toxin and place it into a plant. The first genetically engineered crop was the corn and was registered with the EPA in 1995.

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