| Bacillus thuringiensis (Bt), the leading biorational pesticide is a ubiquitous gram-positive, spore-forming bacterium that forms a parasporal crystal during the stationary phase of its growth cycle. It is important to study the human and environmental safety of using Bt microbial pesticides around the world. DNA chip was developed to determine whether there is Bt in certain agricultural products. Meanwhile the practicability of DNA chip in detection of bacteria was also investigated.Specific primers were designed to amplify the genes of Bacillus thuringniensis subsp. israelensis (Bti). 18 Bti DNA fragments were prepared by PCR and RD technology as probes . The PCR products of small DNA fragments (<800bp) were purificated and directly cloned into the pMD18-T vectors.The PCR products of large DNA fragments ( >1500bp) were classified and re-amplified by RD technology to obtain the fragments for subsequent purification and cloning into the pMD18-T vectors. Followed by rapid identification by gel electrophoresis, the recombinant plasmids were extracted from positive clones and the target gene fragments were sequenced.Total DNAs of Bti and Bacillus thuringniensis subsp. Kustaki (Btk) isolation were labeled with fluorescence and hybridized with microarray. The DNA chip were scanned and main results are as follows:1. Sequence analysis showed that all the fragments amplified were Bti genes.2. RD technology is reliable in breaking down large DNA fragments into confined and shorter gene fragments for preparing microarray probes. The length of probes was 200-800bp and are suitable for hybridizational dynamics on a chip.3. The DNA chip could be used to identify Bti. It is reliable to distinguish the Bti from Btk. This kind of method in development of DNA chip in detection of bacteria is practicable.4. Bt and the Bt DNA Chip can be a model system in further detection ofbacteria of the Bacillus family, like the Bacillus Anthracis, which is one of the most threatening bacteria pathogen.
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