- 作者: Suh-Der Tsen a, Suh-Sen Fang a, Mei-Jye Chen a, Jun-Yi Chien a, Chih-Chun Lee a, Darwin Han-Lin Tsen b
- 作者服務機構: a Department of Microbiology, Graduate Institute of Microbiology and Immunology, National yang-Ming University and b Taipei American School, Taipei, Taiwan, ROC
- 中文摘要: --
- 英文摘要: mids, a most frequent sequence was identified. Thissequence resembled the bacterial interspersed mediumrepetitive sequence of E. coli, suggesting the existence ofa recognition sequence. We conclude that plasmid natu-raltransformation exists in E. coli.Although Escherichia coli does not have a natural trans-formation process, strains of E. coli can incorporateextracellular plasmids into cytoplasm‘naturally' at lowfrequencies. A standard method was developed in whichstationary phase celIs were concentrated, mixed withplasmids, and then plated on agar plates with nutrientswhich allowed cells to grow. Transformed cells couldthen be selected by harvesting cells and plating again onselective agar plates. Competence developed in the lagphase, but disappeared during exponential growth. Asmore plasmids were added to the cell suspension, thenumber of transformants increased, eventually reachinga plateau. Supercoiled monomeric or linear concatemer-is DNA could transform cells, while linear monomericDNA could not. Plasmid transformation was not relatedto conjugation and was recA-independent. Most of theE. coli strains surveyed had this process. All tested plas-mids, except pACYC184, could transform E. coli. Inser-tion of a DNA fragment containing the ampicillin resis-tance gene into pACYC184 made the plasmid transform-able. By inserting random 20-base-pair oligonucleotidesinto pACYC184 and selecting for transformable plas-
- 中文關鍵字: --
- 英文關鍵字: Transformation, Natural transformation, plasmid Escherichia colitransformation, Transformation