Mutagenic DNA repair in Escherichia coli

Summary Escherichia coli K12 Hfr H Tsx^s Str^s and F^- Pro^- Tsx^r His^- Arg^- Str^r bacteria were conjugated in the absence of arginine with or without glucose. The efficiency of conjugation, measured by the frequency of Pro⁺ and His⁺ recombinants was not affected. Arginine starvation alone did not affect the tsx^s gene expression which occurred in all the zygotes which had received the gene. In contrast, argine and glucose starvation allows tsx^s expression only in those zygotes in which the donor gene had been integrated in the genome. As the glucose starvation brings on a destabilization of the messenger RNA synthesized by the F^- cells in absence of arginine, the results can be interpreted as follows: the transferred tsx^s genes are transitorily expressed in all the zygotes at the unintegrated state. After this transient period, only those genes integrated in the chromosomes of the zygotes continue to be expressed.