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Bacillus thuringiensis - Bacterial Insecticide

June 24, 2003

Microbiologists in Europe have played a major role in developing the Bacillus thuringiensis story, as they have in many areas of research.

FEMS, The Federation of European Microbiological Societies, is now embarking on a series of major European Congresses bringing together scientists from all parts of Europe and providing a forum for the promotion of microbiology as a crucial resource for the development of a sustainable and healthy society in the twenty-first century.

The first of the series will be held in Ljubljana, Slovenia, June 29 - July 3, 2003.

Bacillus thuringiensis - or Bt as it is usually called - was one of the earliest bacteria to be seen and recognised for what it is: a potent pathogen causing a rapidly spreading and fatal infection in caterpillars. It was about 1850 that Louis Pasteur, the father of microbiology, saw the rodshaped, spore-bearing cells in the bodies of silkworms suffering from a disease called flacherie and correctly described them as being the cause of the infection. As time passed it was recognised that different strains of the bacterium would infect insects other than silkworms, some of them important pests of food and agricultural crops.

The idea of using a bacterial disease to control harmful pests was an attractive one and the first bacterial insecticide was marketed in France just before the Second World War. It was a suspension of spores of Bt and it was fairly effective in killing the European Corn Borer in the field. A German bacteriologist, Berliner, had isolated Bt in 1915 from infected Flour Moth larvae - he worked in the province of Thuringia and gave the bacterium its name. Berliner noticed that alongside the spore a second, dense body grew in the bacterial cell. Soon after the end of the Second World War this so-called parasporal body was shown to be a beautiful crystal of protein - a pro-toxin that, when activated by the digestive juices of the caterpillar, released a potent toxin that attacked the wall of the gut and initiated changes that killed the host.

During the latter half of the 20th Century many products appeared on the market and found some application as sprays or dusts to treat crops and garden plants. They had two attractive features; they proved to be completely safe in use - the receptor molecules to which the toxin attached are not found in mammals or other beneficial life-forms - and they were judged to be "organic". The genes controlling the production of the protein toxin were isolated during the 1990s and a major development took place in 1998 when a Bt toxin gene was inserted into the cells of a tobacco plant, which proved to be resistant to insect attack; it had its own built-in insecticide.

Today much of our corn is produced from plants containing toxin genes and several other important crop plants, such as cotton, are protected from insect attack in the same way. Naturally not everyone is happy about the use of genetically modified plants in this way and Bt, once the darling of the Organic lobby, now finds itself at the centre of a vigorous social and political debate. That debate and the science behind it provide typical examples of the themes that will be explored in depth at the 1st First Congress of European Microbiologists to be organised by FEMS, in Slovenia, June 29 - July 3, 2003.

Cankarjev dom