A strain of Bacillus thuringiensis, named Bt 1-3, was isolated from Korean soil sample and it showed high insecticidal activity against Plutella xylostella. Bt 1-3 was deterimined to belong to ssp. aizawai (H7) by an H antiserum agglutination test and produced bipyramidal-shaped crystal proteins. PCR analysis with specific cry gene primers showed that Bt 1-3 contained cry1Aa, cry1Ab, cry1C, cry1D and cry2Ab genes. In addition, this isolate showed high uptake rate of foreign plasmid by electroporation. Based on these characteristics of Bt 1-3, we tried to construct a spore-free Bt 1-3 mutant by knock-out sigG gene, which is known as a key transcription factor during sporulation. First, we constructed a basal vector, named pDST, consisting of erythromycin resistant gene (EmR), partial polyhedrin gene and temperature sensitive origin of replication gene (Orits). Subsequently, according to the chromosomal DNA sequence of Bt subsp. konkukian 97-27, we amplifed upstream and downstream regions of Bt 1-3 sigG, and cloned into pDST (pDST-G). So far, several EmR colonies were obtained by electroporating into the wildtype Bt 1-3 and crossover by homologous recombination is going on.

Research has been in progress for more than a decade to production of useful proteins by genetic modification in cattle. However, the levels of protein production in transgenic cattle have been reported very low. To enhance protein production in transgenic animal, we tried homologous recombination to donor cells for production of transgenic clone cattle through nuclear transfer procedure. Thus, we constructed the two targeting vectors of human thrombopoietin (TPO) at bovine -casein locus using homologous recombination with 13.6 kb and 9.6 kb homology. In two targeting vectors, positive selection was through the neomycin resistance gene and negative selection was by the diphtheria toxin (DT). Gene targeting was attempted in bovine embryonic fibroblasts (bEF) and bovine ear skin fibroblasts (bESF). To determine the most appropriate concentration of neomycin for bEF and bESF, G4l8 resistance was confirmed by culturing the cells in various concentrations of the drug and both of the cells were optimally selected at of neomycin. The transfected bEF and bESF by the targeting vectors were colonized efficiently at the ratio of DNA to transfection reagent such as :2 and :. Comparing number of healthy clones from passage 4 to passage 8, bESF (17%) persist in culture for much longer than bEF (6%). The two gene-targeted bESF clones of 30 random-integrated clones with 9.6 kb homology length were confirmed, however, nothing was out of 72 random integration clones with 13.6 kb homology length, The DT also worked more efficiently in clones transfected with the vector of 9.6 kb homology length. Our data suggests that the choice of donor cell for long culture period should be considered to obtain targeted cell clone, and the gene-targeting frequency and the DT working efficiency are dependent on the length of target homology.

단백질분해효소를 생산하지 않는 균주 B. subtilis MT-2의 염색체 DNA를 추출한 다음, B. subtilis AC819 균주에 상동성 유전자재조합을 이용하여 competent cell 형질전환을 시켰다. 얻어진 형질전환체를 B. subtilis HL-1이라고 명명하였으며, 그 표현형은 histidine 요구성, streptomycin 내성, tetracyclin 내성을 나타내면서 단백질 분해효소를 생산하지 않았다. 플라스미드 pUB11