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Bacteria for plague control in agriculture

Bacillus thuringiensis, a spore bacteria discovered in 1901 by the Japanese scientist Ishiwata and, ten years later, by the German scientist Berliner came across his findings. It is the micro-organism most used as a bio-insecticide throughout the world. It is a bacterium found naturally in ecosystems, frequently on floors and on the surface of leaves and in practically all habitats.

But, above all, it is a bacteria which synthesises a series of proteins which crystallise and have a toxic capacity for some insects. This crystalline form is actually what can be used as the active ingredient in any bio-insecticide. These proteins are activated by ingestion and, in a matter of hours, produce irreversible damage in the cell walls of the digestive tract producing paralysis therein. The insect dies of hunger or, when the bacterial spores manage to penetrate and germinate in the haemocoelic cavity, the insects die from septicaemia.

With Bacillus thuringiensis, more than 200 different toxic proteins have been identified to date and which offer a valuable natural resource for their use in plague control.

Non-contaminant, non-toxic bacterial lines

The advantages of their use as bio-insecticides are many: they are highly specific and do not contaminate the environment as they are not toxic to other insects, plants, land and aquatic animals, nor for humans.

The research centres on the identification and investigation of new toxins from this bacterium for use against the Helicoverpa armigera insect. Also the bio-insecticide bio-technologogy of Bacillus thuringiensis needs a great improvement on products currently on offer in at least three aspects: in the innovation of production processes, in the innovation of lines for creating toxins production and in the search for new toxins.

The results of the study not only permits the identification of lines which can be used as bio-insecticides, but can isolate the genes responsible for the toxic proteins (genes cry). The synthesised protein is in fact a protoxin and only becomes a toxin in the medium conditions of the digestive tract of the Helicoverpa armigera. In the tracts of other animals present in natural ecosystems, humans included, these conditions are not met and so the mentioned proteins are inoffensive for them. Thus, we have the security that these bacteria can be used as bio-insecticides.

Elhuyar Fundazioa. February 2003.

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