Japanese biologist, Shigetane
Ishiwatari was investigating the cause of the sotto disease (sudden-collapse
disease) that was killing large populations of silkworms when he first isolated
the bacterium Bacillus thuringiensis (Bt) as the cause of the disease in 1901.
Ernst Berliner isolated a bacteria that had killed a Mediterranean flour moth in
1911, and rediscovered Bt. He named it Bacillus thuringiensis, after the German
town Thuringia where the moth was found. Ishiwatari had named the bacterium
Bacillus sotto in 1901 but the name was later ruled invalid. In 1915, Berliner
reported the existance of a crystal within Bt, but the activity of this crystal
was not discovered until much later.
Farmers started to use Bt as a pesticide in 1920. France soon started to make
commericialized spore based formulations called Sporine in 1938. Sporine, at the
time was used primarly to kill flour moths.
More products containing Bt were marketed, but many of these products had
limitations. Bt products such as sprays are rapidly washed away by rain, and
degrade under the sun's UV rays. Also, there were many insects that are not
susceptible to any of the limited number of Bt strains known at the time. All
the Bt strains known at the time were toxic to lepidopteran (moth) larvae only.
There were also some insects that live within the plant or underground where the
Bt sprays could not reach. Since synthetic insecticides were readily avaliable
and often very efficient in killing insects, Bt was not used widly.
In 1956, researchers, Hannay, Fitz-James and Angus found that the main
insecticidal activity against lepidoteran (moth) insects was due to the
parasporal crystal. With this discovery came increased interest in the crystal
structure, biochemistry, and general mode of action of Bt. Research on Bt began
in ernest.
In the US, Bt was used commercially starting in 1958. By 1961, Bt was registerd
as a pesticide to the EPA.
Up until 1977, only thirteen Bt strains had been described. All thirteen
subspecies were toxic only to certain species of lepidopteran larvae. In 1977
the first subspecies toxic to dipteran (flies) species was found, and the first
discovery of strains toxic to species of coleopteran (beetles) followed in 1983.
In the 1980's use of Bt increased when insects became increasingly resistant to
the synthetic insecticides and scientists and environmentalists became aware
that the chemicals were harming the environment. Bt is organic and it affects
specific insects and does not persist in the environment. Because of this,
governments and private industries started to fund research on Bt.
Today, there are thousands of strains of Bt. Many of them have genes that encode
unique toxic crystals in their DNA.
With the advancement in molecular biology, it soon became feasible to move the
gene that encodes the toxic crystals into a plant. The first genetically
engineered plant, corn, was registered with the EPA in 1995. Today, GM
(genetically modified) crops including, potato and cotton are planted throughout
the world.