Study on the heredity stability of a recombinant plasmid pMal--2X in {\sl Escherichia coli}

The strain of TB1 from the original stock which harboring a recombinant plasmid pMal-2X including apc gene from cyanophyceae had been subcultured serialyto 100~(th) generation in Amp~(+) plate. The growth characteristics and the morphology of the cultures did not show differences among the generations. The chromatogram of the plasmids in different generations digested by EcoRⅠ restriction enzymes were same, as well as DNA sequences showed no difference among generations. In addition to that, origin strain and 10~(th), 20~(th), 50~(th) and 100~(th) generation strain had a similar rAPC expression level. The immunology activity of the rAPC and SDS-PAGE of the proteins expressed in different generations were also same. From the above results, it is indicated that recombinant stain P1 has a high hereditable stability.