온도감수성 대장균 M5248 균주에 있어서의 plasmid $pPL-lambda$와 pAS1을 $30^{circ}C$에서 형질전환 시킬 때의 조건을 조사한 바 배양시간에 있어서는 균주의 대수 증식기 중반인 2시간 30분 배양시, 즉 cell농도는 $4.5 imes10^7;cells/ml$이며 파장 590nm에서의 흡광도가 0.45 일 때 plasmid $pPL-lambda$와 pAS1 모두 형질전환율은 $2.4 imes10^6$과 $1.5 imes10^{-6}$로서 가장 높았다. 그리 고 competent cell $200{mu}l(9 imes10^{-6}cell)$에 대하여 plasmid 농도가 $6.4{mu}g/ml$ 형질전환율이 $4.4 imes10^{-6}$로서 높게 나타났으며 이때 calcium chloride만으로 처리한 것 보다 calcium chloride와 thymidine을 혼합하여 처리했을 때 2배 정도 더 많은 transformant를 유도하였다. Ampicillin 내성유전자는 LB배지를 첨가하여 $30^{circ}C$에서 2시간 동안 배양했을 때 그 형질이 표현되었다.
The transformational conditions of plasmids $pPL-lambda$ and pAS 1 are as follows in E. coli, Ts-mutant M 5248 strain at $30^{circ}C$. When the culture time was 2.5 hours of mid logarithemic phase, the cell concentration was $4.5 imes10^7;cells/ml$, the optical density was equal to 0.45 at 590 nm wave length, the transformational frequencies of plasmid$pPL-lambda$ and pAS 1 had the highest values as $2 imes10^{-6};and;1.5 imes10^{-6};and;1.5 imes10^{-6}$ and respectively. For $9 imes10^6$ competent cells in $200{mu}l$, the transformational frequency was as high as $4.4 imes10^{-6}$ at 510 ng plasmid concentration. The competent cells treated with the mixture of calcium chloride and thymidine twice rates of transformation than those treated with calcium chloride. The ampicillin resistance of transformants was expressed in LB broth after 2 hours at $30^{circ}C$.
