The Functional Groups of Micro-organisms Used as Bio-indicator on Soil Disturbance Caused by Biotech Products such as Bacillus thuringiensis and Bt Transgenic Plants

Insects are usually controlled with insecticides. Of the insecticides 5 % are biological, and more than 90 % of biological insecticides are based on Bacillus thuringiensis (Bt; Sanchis 2000). The use of bio-insecticides has increased because of the growing need to obtain better quality food and to protect the environment, but very little is known about the impact these organisms have on the environment and mainly on the soil functional microorganism groups.

Due to the efficiency of bio-insecticides based on B. thuringiensis, the gene which produces the bio-insecticide crystal was introduced into plants to produce Bt-transgenic plants. Transformed tobacco using the Ti plasmodium from Agrobacterium tumefasciens was obtained in the 1980s. Later, the electroporation and bombardment or bio-ballistic of embryos method, which is more efficient for transformation of a greater number of plant species with the cry B. thuringiensis gene, was used (Peferoen 1997). The second generation of Bt-transgenic plants is presently obtained with the introduction of at least two cry genes in the plant genome, and there are already more than 20 species of transgenic plants of economic importance being used in a few countries (Sanchis 2000).

Although transgenic plants have been produced and sown for two decades, there is little information about their environmental impact. Currently proposed plant gene products will probably have less impact on soil ecosystems than some familiar and accepted practices. However, some transgenic plant products may have measurable adverse effects on soil organisms that will have to be monitored for some years after widespread introduction