Effect of glucose starvation on the expression of transferred tsx genes in Escherichia coli K12 zygotes.

Escherichia coli K12 Hfr H Tsxs Strs and F- Pro- Tsxr His- Arg- Strr 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 tsxs gene expression which occurred in all the zygotes which had received the gene. In contrast, argine and glucose starvation allows tsxs 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 tsxs genes are transitorily expressed in all the zygotes at the unintegrated state. After this transient period, only thsoe genes integrated in the chromosomes of the zygotes continue to be expressed.