Abstract

Stabilization by the mini-F fragment of a pBR322 derivative bearing the tryptophan operon in Escherichia coli.
Agric. Biol. Chem. 49: 3619-3622. 1985.
H. Yukawa, Y. kurusu, M. Shimazu, M. Terasawa, A. Ohta and I. Shibuya.
In an Escherichia coli K-12 strain (trpA trpE tna) cultured in LB broth without selective pressure, a pBR322 derivative bearing the E. coli tryptophan operon (pBR322-trp) was rapidly lost: after 27 cell-number doublings, only 7% cells retained both tryptophan prototrophy (Trp+)and ampicillin resistance (Apr), and 17% were Apr but Trp-. Insertion of the mini-F DNA from F factor into this plasmid effectively suppressed both the plasmid loss and the discoordinate loss of Trp+: the persentage of Trp- cells per cell number doubling was decreased more than 100-fold. Partial derepression of the trp operon due to 3-indole acrylic acid further decreased the stability of the pBR322-trp but not that of the mini-F-inserted pBR322-trp.